
^{12}C (2017KE05)(See Energy Level Diagrams for ^{12}C and Isobar Diagram) See also 2 [Electromagnetic Transitions in A = 12] (in PDF or PS), 12.13 [Energy levels of ^{12}C] (in PDF or PS) and 12.14 [The decay of some ^{12}C levels] (in PDF or PS).
< r^{2}_{matter} >^{1/2} ≈ 2.352.48 fm; i.e., see (1985TA18, 2001OZ04, 2011AL23, 2016KA37). ^{12}C*(4.44): Q = 6 ± 3 e ⋅ fm^{2}, indicating a substantial oblate deformation (1983VE01). g_{J} (^{12}C^{5+})[electronic gfactor] = 2.0010415963 (10)_{exp} (44)_{me} (2002BE82).
The γ_{03} excitation functions from the ^{6}Li + ^{6}Li capture reaction were measured for E_{cm} = 1 to 8 MeV (1991EU01). Evidence is found for a state at E_{x} = 30.33 MeV with Γ ≈ 0.8 MeV. A comparison with other data, mainly from other ^{6}Li + ^{6}Li decay channels and ^{9}He(^{3}He, γ) suggests the resonance results from a concentration of J^{π}; T = 2^{+}; 0 and 2^{}; 1 strength.
The excitation functions for some final states in ^{11}B and ^{11}C (reactions (a) and (b)) are structureless while others (to states with J^{π} = 3/2^{}, 5/2^{}, 5/2^{+}) exhibit pronounced structures. The most prominent of these is observed at E(^{6}Li) = 8.4 MeV [^{12}C*(32.4)] in the p_{2} and n_{2} yields with a width Γ_{cm} ≈ 1 MeV (1987DO05). Reaction (d) has been studied in kinematically complete experiments at E(^{6}Li) = 2.4 to 6.7 MeV (1988LA11) and at E(^{6}Li) = 2.5 and 3.1 MeV (2015SP01, 2015TU06). See also (1984LA19, 1987LA25). For reactions (e) and (f) see (1983WA09). Broad structures have been observed in the elastic scattering at E(^{6}Li) ≈ 13 and 26 MeV: see (1980AJ01). See also (1990AJ01).
This reaction and the Hoyle state ^{12}C*(7.65) resonance state are of great importance to nucleosynthesis and the formation of heavy elements; see (1985CA41, 1987DE13, 1998TH07, 2000FI14, 2001CS04, 2010OGZX, 2010UM01, 2013EP01, 2013NG01, 2015FI03, 2016ME03, 2016SU25). In (2010UM01), nonresonant capture to a linear configuration that transitions to a triangular orientation is suggested. Production rate sensitivities to stellar environment variables are investigated in (2010DE18, 2011AU01), and the impact of time variation of the fundamental constants is studied in (2012CO19). Also see a prediction for the J^{π} = 0_{3}^{+} state at E_{res} = 1.66 MeV in (2010KAZK).
Excitation functions and angular distribution studies have been carried out at E(^{3}He) = 1.0 to 6.0 MeV (1972BL17: γ_{0}, γ_{1}, γ_{2}), E(^{3}He) = 1.5 to 11 MeV (1972LI29: γ_{0}, γ_{1}, γ_{2}, γ_{3}), E(^{3}He) = 2 to 4.5 MeV (1964BL12: γ_{0}, γ_{1}) and E(^{3}He) = 3 to 26 MeV (1974SH01: γ_{0}, γ_{1}, γ_{2}, γ_{3}). Observed resonances are shown in 12.15 (in PDF or PS). See (1980AJ01) for references. ^{12}C*(28.2) appears to be formed by s and dwave capture. The γ_{0} and γ_{2} transitions to the 0^{+} states ^{12}C*(0, 7.7) are strong and show a similar energy dependence. A strong nonresonant contribution is necessary to account for the γ_{1} yield (1972BL17). The resonance structure reported by (1974SH01) appears to confirm the role of 3p3h configurations for ^{12}C excitations somewhat above the giant resonance region. The γ_{3} yield is relatively unstructured (1972LI29, 1974SH01: to E(^{3}He) = 26 MeV). See also (1975AJ02). (1970BL09) had reported a capture resonance at E(^{3}He) = 1.74 MeV which subsequently decayed via ^{12}C*(15.11) and which was assumed to correspond to the first J^{π} = 0^{+}; T = 2 state in ^{12}C [E_{x} = 27.585 ± 0.005 MeV]. However, neither (1972HA63) nor (1972WA18) have been able to repeat this observation: Γ_{3He}Γ_{γ}/Γ < 1.5 meV (1972WA18), < 2 meV (1972HA63).
Excitation functions for neutrons, production cross sections for ^{11}C and polarization observables have been measured at E(^{3}He) = 1.2 to 10 MeV for several neutron groups. No sharp structure is observed, but there is some suggestion, from angular distribution data and the excitation function at forward angles, for a structure (Γ ≈ 350 keV) at E(^{3}He) ≈ 2 MeV: E_{x} = 27.8 MeV (1963DU12, 1965DI06). The total cross section for ^{11}C production shows a broad maximum, σ = 113 mb at E(^{3}He) = 4.3 MeV. In the range E(^{3}He) = 5.7 to 40.7 MeV the yield decreases monotonically. Excitation functions and angular distributions for protons (reaction (b)) have been measured for E(^{3}He) = 1.0 to 10.2 MeV for a number of proton groups. No pronounced structures are reported. Analyzing powers have been measured at E(pol. ^{3}He) = 33.3 MeV for nine deuteron groups (reaction (c)). The cross section for groundstate tritons (reaction (d)) increases monotonically for E(^{3}He) = 2.5 to 4.2 MeV and then shows a broad maximum at E(^{3}He) ≈ 4.5 MeV. See also (1993AR14, 1996AR07: E = 22.3 to 34 MeV). The excitation function for elastic scattering (reaction (e)) decreases monotonically for E(^{3}He) = 4.0 to 9.0 MeV and 15.0 to 21.0 MeV. See also (1992AD06: E = 50, 60 MeV). At θ_{cm} = 111° a slight rise is observed for E(^{3}He) = 19 to 21 MeV. Polarization observables have been reported at E(^{3}He) = 18, 31.4 and 32.8 MeV. Excitation functions for the α_{0} group (reaction (f)) have been reported for E(^{3}He) = 2 to 10 MeV (1978BI15): evidence is found for a resonance at E_{x} ≈ 29.3 MeV. See also (1992AD06). Analyzing powers have been measured at E(pol. ^{3}He) = 33.3 MeV. For reaction (g) see (1986LA26, 1987WA25). See references and additional work in (1968AJ02, 1975AJ02, 1980AJ01, 1985AJ01, 1990AJ01).
Neutron groups have been observed to ^{12}C*(0, 4.4, 7.7, 9.6, (10.1), (10.8)). Angular distributions of neutrons, mainly for n_{03}, have been measured at energies in the range E_{α} = 1.75 to 32 MeV. Gammaray angular distributions have been studied by (1955TA28, 1959SM98, 1963SE04). Observation of the γdecay of the 15.1 MeV level is reported by (1954RA35, 1957WA04). At E_{α} = 35 MeV the members of the K^{π} = 0^{+} band and ^{12}C*(9.63) are strongly populated (1981HAZV). Doppler shift measurements on the transition ^{12}C*(4.4 → g.s.) yield mean life values of τ_{m} = 50 ± 6 fsec (1961DE38); 57^{+23}_{17} fsec, Γ_{γ} = (11.5^{+5}_{3.2}) meV (1966WA10); < 48 ± 10 fsec (1967CA02). The internal pair conversion coefficient indicates an E2 transition (1954MI68): the pair angular correlation permits M1 or E2 and favors the latter (1954HA07, 1956GO1K, 1956GO73, 1958AR1B). Angular distributions of n_{1} and n_{1}γ correlations strongly indicate a direct interaction mechanism even at E_{α} = 3.3 and 5.5 MeV (1960GA14, 1962KJ01); also see correlation studies at E_{α} = 1.4 to 4.5 MeV (2010GI07). ^{12}C*(7.65[J^{π} = 0^{+}]) decays predominantly into ^{8}Be + α with a small radiative branch. In (1960AL04, 1972OB01) the pair decay is measured Γ_{π}/Γ = (6.9 ± 2.1) × 10^{6}; this supercedes the earlier value Γ_{π}/Γ = (6.6 ± 2.2) × 10^{6} (1959AL97, 1960AJ04, 1960AL04, 1961GA03). However, see 12.14 (in PDF or PS). Neutron catalyzed helium burning, i.e. ^{4}He(αn, γ)^{9}Be(α, n)^{12}C, is analyzed in (1994WR01, 1996KU07, 2009GI03, 2011GI05). The ratio, Yield(E_{γ} = 4.44 MeV)/Yield(neutrons) = 0.596 ± 0.017, was measured for an AmBe source in (2004MO18). The energy dependent reaction cross sections have been evaluated at E < 10 MeV for actinideBe neutron source energy distributions (2003SH22). Also see (1997HE11, 2000MI34, 2007AH07, 2007MA58, 2015VL01). Reaction (b) was measured at E_{α} = 22 to 30 MeV, along with ^{12}C(α, 3α)^{4}He, in search of ^{12}C resonances above E_{x} = 7 MeV that could have structures related to the Hoyle state (2011FR02). The analysis separately considered both events populating natural parity states involving ^{12}C* → ^{8}Be_{g.s.}(J^{π} = 0^{+}) + α and events that excluded ^{12}C* → ^{8}Be_{g.s.} + α. Known states at E_{x} = 9.64, 10.84, 11.83, 12.71, 14.08 are observed in the ^{9}Be(α, ^{12}C) reaction along with a state consistent with E_{x} = 13.3 ± 0.2 MeV and Γ = 1.7 ± 0.2 MeV. Analysis of the angular correlations from the ^{12}C(α, 3α) reaction support J^{π} = 4^{+} for the new state.
At E(^{6}Li) = 32 MeV angular distributions have been studied to ^{12}C*(0, 4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 14.1); ^{12}C*(9.64) is relatively strongly populated. There is no indication of the T = 1 states (1986AS02: FRDWBA). Similar results are found for E(^{9}Be) = 26 MeV in (1975VE10).
At E(^{9}Be) = 40 MeV, angular distributions to ^{12}C*(0, 4.44, 7.65, 9.64, 13.35, 14.08) were measured (1992CO05); the data are consistent with direct ^{3}He cluster transfer. Cluster spectroscopic factors are deduced. Also see measurements at E(^{9}Be) = 26 MeV, θ = 10° to ^{12}C*(4.4, 7.7, 9.6) (1975VE10).
At E(^{10}C) = 10.7 MeV, the αparticle correlations from ^{12}C*(7.65, 9.64) were studied in search of evidence supporting direct 3body breakup (2012MA10), as suggested in (2011RA43). Results were consistent with 100% decay via ^{8}Be_{g.s.} + α in both cases.
At E(^{3}He) = 13 MeV neutron groups are observed to ^{12}C*(0, 4.4, 7.7, 16.1, 17.8) and to excited states at E_{x} = 23.53 ± 0.04 [Γ < 0.4 MeV] and 27.611 ± 0.020 MeV. The latter is formed with a 0° cross section of ≈ 200 μb/sr and is taken to be the first 0^{+}; T = 2 state of ^{12}C (1974GO23).
The (d, γγ) excitation function [via the J^{π} = 1^{+}; T = 1 state at E_{x} = 15.1 MeV] has been measured for E_{d} = 2.655 to 2.84 MeV. The nonresonant yield of 15 MeV γrays is due to direct capture processes or to a very broad resonance: no sharp resonances are observed corresponding to the E_{x} ≈ 27.6, T = 2 state reported in other reactions [Γ_{d0}Γ_{γ}/Γ ≲ 0.2 eV] (1970BL09).
The thintarget excitation function, measured at E_{d} = 0.3 to 4.6 MeV, shows some indication of a broad resonance in the forward direction near E_{d} = 0.9 MeV. Above E_{d} = 2.4 MeV, the cross section increases rapidly to 210 mb/sr at 3.8 MeV and then remains constant to 4.6 MeV (1954BU06, 1955MA76). Also see activation measurements reported at E_{d} = 0.5 to 6 MeV (1990MI11). The 0° excitation function for ground state neutrons shows no structure for E_{d} = 3.2 to 9.0 MeV (1967DI01). Excitation functions have been measured for E_{d} = 7.0 to 16.0 MeV (1981AN16). The excitation function for neutrons to ^{11}C*(6.48) increases monotonically for E_{d} = 4.0 to 4.8 MeV (1972TH14). The branching ratios at 90° for the transitions to the ground states of ^{11}C and ^{11}B [n_{0}/p_{0}] have been measured for E_{d} = 1.0 to 2.0 MeV by (1973BR24). At E_{d} = 1 to 5 MeV, cross sections have been obtained for the neutrons and protons to the second, third, fourth, and fifth excited states of the ^{11}B and ^{11}C mirror nuclei (1967SC1K). The angular distributions all show a sharp peak around 20° and a smaller contribution in the backward direction; DWBA produces a satisfactory fit to these distributions (1967DI01). Polarization measurements have been carried out for E_{pol. d} = 2.5 to 4.0 MeV (1967ME1N), E_{pol. d} = 1.20 to 2.90 MeV (1968BR26: n_{0}) and E_{pol. d} = 2.4 to 4.0 MeV (1972ME06: n_{0}, n_{1}, n_{2+3}). The transitions to ^{11}C*(0, 4.32 + 4.80) appear to involve a direct reaction mechanism (1972ME06). Cross sections and astrophysical Sfactors for n_{0} are reported for E_{d} < 160 keV (2008ST10). Thicktarget yields and astrophysical Sfactors are reported for neutrons at E_{d} = 24 to 111 keV (2001HO23) and for 4.3 MeV γrays at E_{d} = 111 to 170 keV (1982CE02). Methods of ^{11}C production for position emission tomography are discussed in (1989ST09, 2005VO15, 2011KI04).
Angular distributions and yields of protons have been measured for E_{d} = 0.9 to 2 MeV (2007KO69) and E_{d} = 15.3 MeV (2005GA59); also see results reported at E_{d} = 0.18 to 3.1 MeV (1959AJ76), 0.14 to 12 MeV (1968AJ02) and 0.7 to 2.9 MeV (1975AJ02). Although the excitation functions show several broad peaks, no clear resonances can be identified, and it is assumed that many overlapping resonances are involved (1956MA69) except possibly at E_{d} = 2.3 MeV (E_{x} = 27.1 MeV) where the effect of a broad resonance influences the cross section of the p_{1} and p_{3} groups. An analysis given in (2005RU16) suggests the broad peaks correspond to fragmented J^{π} = 1^{} components of the GDR at E_{res}(cm) = 0.38, 0.61, 1.61 MeV with Γ = 0.37, 0.37 and 1.24 MeV, respectively, as well as a J^{π} = 2^{+} contribution from the GQR at E_{res}(cm) = 1.36 MeV with Γ = 710 keV. The p_{2}γray correlations were measured in (2005GA59). Cross section ratios for the (d, n) and (d, p) reactions to mirror states have been measured by (1967SC1K, 1973BR24). The astrophysical relevant region has been studied at E_{d} = 57 to 141 keV (1993CE02, 1997YA02, 1997YA08), 91 to 161 keV (1981CE04) and 120 to 340 keV (2001HO22) and at E_{cm} = 100 to 300 keV (2004RU10). Polarization studies have been carried out at E_{pol. d} = 6.9, 10, 11 to 13.8, 11.4 and 21 MeV [See (1968AJ02)] and at E_{pol. d} = 1.15, 1.40 and 1.85, 10, 12 and 13.6 MeV [see (1975AJ02)].
The yield of elastically scattered deuterons has been measured for E_{d} = 1.0 to 2.0 MeV: resonances at E_{d} = 1.0 and 1.9 MeV are suggested by (1969LO01). Excitation functions for the deuterons to ^{10}B*(1.74, 2.16) [J^{π}; T = 0^{+}; 1 and 1^{+}; 0, respectively] have been measured at several angles for E_{d} = 4.2 to 16 MeV: they are characterized by rather broad, slowly varying structures. The ratio σ_{1.74}/σ_{2.16} varies from (0.69 ± 0.04)% at E_{d} = 6.5 MeV to (0.16 ± 0.04)% at E_{d} = 12.0 MeV corresponding, respectively, to isospin impurities of ≈ 2% and ≈ 0.5% (1974ST01). No resonance structure is observed in the elastic yield for E_{d} = 14.0 to 15.5 MeV (1974BU06). Polarization measurements are reported at E_{pol. d} = 12.5 MeV (1975ZA08) and at 15 MeV (1974BU06).
Excitation functions have been measured for the α_{0} and α_{1} groups for E_{d} = 0.4 to 12 MeV [see (1968AJ02, 1975AJ02, 1980AJ01)] and for E_{d} = 0.9 to 2.0 MeV (2007KO70: α_{0}). Maxima in the α_{0} yields are reported at E_{d} = 1, 2, 4.5 and (6) MeV. The first is attributed to an swave resonance corresponding to a state with E_{x} ≈ 26.0 MeV, Γ ≈ 0.5 MeV (1968FR07). The resonance structures at ≈ 2.0 and 4.5 MeV (Γ ≳ 1 MeV) may both involve the isoscalar giant resonance: E_{x} ≈ 28 MeV, Γ ≈ 4 MeV (1978BU04). No evidence for the T = 2 state was found in the α_{0} and α_{1} yield curves taken in 2 keV steps for 27.35 < E_{x} < 27.65 MeV (1970BL09). For yields of the αparticles to ^{8}Be*(17.6, 18.1) see (1970CA12). Cross sections, angular distributions and Sfactors are deduced in (2001HO22: E_{d} = 120 to 340 keV) and (1993CE02, 1997YA02, 1997YA08: E_{d} = 57 to 141 keV). Reaction (b) has been studied for E_{d} = 2.7 to 5.0 MeV (1975RO09, 1975VA04, 1977GO16), E_{d} = 0.36 MeV (1977NO10), E_{d} = 2.5 and 3 MeV (1992KO26), E_{d} = 13.6 MeV (1981NE08, 1992PU06) and E_{d} = 48 MeV (1993PA31). The work of (1977NO10) suggests that J^{π} = 3^{} and 4^{+} ^{12}C compound states with unidentifiable energies and widths contribute dominantly to the sequential decay. Also see (1990NE15, 1991AS02).
Observed proton groups are displayed in 12.16 (in PDF or PS). Angular distributions of many of these groups have been measured for E(^{3}He) = 2.0 to 3.0 MeV (1965BH1A), 3.7 MeV (1962BR10), 10.1 MeV (1962AL01) and 14 MeV (1967CO1F). Also see 12.17 (in PDF or PS), which has results from complete kinematics studies of ^{10}B(^{3}He, p3α) and ^{11}B(^{3}He, d3α) given in (2007BO49, 2009KI13, 2010KI08, 2011AL28, 2012AL22, 2012KI07, 2013KI07). 12.14 (in PDF or PS) summarizes the electromagnetic decay parameters of some of the excited states of ^{12}C including results below. Pair emission from ^{12}C*(7.65) has been measured: Γ_{π}/Γ = (6.6 ± 2.2) × 10^{6} [see 12.14 (in PDF or PS)] as has the cascade through ^{12}C*(4.4): Γ_{γ}/Γ = (3.3 ± 0.9) × 10^{4} (1961AL27). By observation of ^{12}C recoils, a value Γ_{rad}/Γ = (3.5 ± 1.2) × 10^{4} is found by (1964HA23). For ^{12}C*(12.71) Γ_{γ0}/Γ = (1.93 ± 0.12)%, Γ_{γ1}/Γ_{γ0} = (15.0 ± 1.8)% and Γ_{α}/Γ = (97.8 ± 0.1)% (1977AD02). See earlier reported results of Γ_{γ}/Γ_{α} = (3 ± 1)% (1958MO99) and (2 ± 1)% (1959AL96): the γdecay branching ratios are reported; see comments in 12.16 (in PDF or PS). The α breakup of ^{12}C*(12.71) shows a triplepeaked αparticle spectrum, characteristic of the breakup of a J^{π} = 1^{+} state (1967BH1B). For ^{12}C*(14.08) the branching ratio Γ_{α}_{0}/Γ is 0.1  0.4. Protonα correlations require J ≥ 2 (1966WA16). ^{12}C*(15.11: J^{π} = 1^{+}; T = 1) decays by γemission mainly to ^{12}C_{g.s.} and has weaker transitions to ^{12}C*(4.4, 7.7, (10.3), 12.7) (1972AL03, 2009KI13): see 12.16 (in PDF or PS). Earlier measurements reported the feeding to ^{12}C_{g.s.} as 97% and to ^{12}C*(4.4) as (3.1 ± 0.6)% (1959AL96), (4 ± 1)% (1960AL14); Γ_{α}/Γ < 0.2 (1960MI1E), < 0.05 (1965AL1B), < 0.10 (1966WA16), respectively. The strong inhibition of the transition to ^{8}Be*(2.9) is cited as evidence for a high isospin purity (1965AL1B). For a study of the chargedependent matrix element between ^{12}C*(12.7, 15.1) see 12.18 (in PDF or PS). Decays of ^{12}C*(16.11, 16.57) populate both ^{8}Be*(0, 2.9). The consequent assignment of natural parity is consistent with J^{π} = 2^{+} for the former but not with the accepted J^{π} = 2^{} for the latter. For ^{12}C*(16.1) Γ_{γ1}/Γ = (2.42 ± 0.29) × 10^{3}, Γ_{γ0}/Γ_{γ1} = (4.6 ± 0.7)%, Γ_{γ}(16.1 → 9.6)/Γ_{γ1} = (2.4 ± 0.4)%, and Γ_{γ}(16.1 → 12.7)/Γ_{γ1} = (1.46 ± 0.25)% (1976AD03, 1977AD02). Also see (1974AN19) who reported Γ_{p}/Γ = (3.24 ± 0.27) × 10^{3} and Γ_{γ}/Γ = (3.23 ± 0.50) × 10^{3}. Reported values of Γ_{α0}/Γ are 0.05  0.12; the decay to 3α occurs rarely, if at all (1966WA16: see however, ^{11}B(p, α)^{8}Be: (1965DE1A)). An unpublished result at E(^{3}He) = 14 MeV, referenced in (1968AJ02), reported two peaks in the giant resonance excitation region corresponding to ^{12}C* ≈ 20.6 and 24.5 MeV, with Γ ≈ 200 and 50 keV, respectively; the angular distributions show forward maxima. Reactions (c) and (d) have been studied by (1970BO39). The latter, at E(^{3}He) = 11 MeV, appears to proceed via a state in ^{12}C at E_{x} = 20.5 ± 0.1 MeV, which is suggested to be J^{π} = 3^{+}; T = 1. The relative intensities of the decays of ^{12}C states with 20 < E_{x} < 25 MeV via channels (c) and (d) is estimated. The α_{0}decay is very small, consistent with the expected population of T = 1 states (1970BO39).
Angular distributions of the deuterons corresponding to ^{12}C*(0, 4.4) have been measured at E_{α} = 15 to 31 MeV [see references in (1968AJ02, 1980AJ01, 1985AJ01, 1990AJ01)]. The dγ_{4.4} angular correlations have been measured for E_{α} = 19 to 30 MeV [see references in (1975AJ02, 1990AJ01)], and see (1989VA07, 2001LE50: E_{α} = 25 MeV). Thick target γray yields were measured in (1995HE40, 1997HE11). At E_{α} = 39.9 MeV, the relative populations of ^{12}C*(12.71, 15.11) [both 1^{+}; the latter isospin forbidden] leads to the value of 285 ± 30 keV (1977LI02) for the chargedependent matrix element between these two states. The spintensor components for ^{12}C*(4.44) formation (1990BO54, 1991BA23, 1998GA46) and induced polarization effects (1999GA43, 2003ZE06) are deduced from analysis of angular distributions at E_{α} = 25 and 30 MeV.
At E(^{6}Li) = 4.9 MeV (1966MC05) angular distributions have been obtained for the αparticles to ^{12}C*(0, 4.4, 7.7, 9.6); the population of ^{12}C*(11.8, 12.7) is also reported. At E(^{6}Li) = 3.8 MeV the intensity ratio for populating the isospin forbidden ^{12}C*(15.11; T = 1) state is (3 ± 2)% of the intensity to ^{12}C*(12.7; T = 0) (1964CA18).
Angular distributions involving ^{12}C*(0, 4.4) have been measured at several energies to E(^{14}N) = 93.6 MeV (1969IS01, 1977MO1A).
(a) Measurements relevant to the astrophysical capture reaction have been carried out at E_{p} = 40 to 180 keV (1992CE02), E_{pol. p} = 80 to 100 keV (2000KE10), E_{p} = 140 to 260 keV (1993AN06) and E_{p} = 160 to 310 keV (2016HE05). (1992CE02) produced γ_{0} and γ_{1} yields and Sfactor related to the measured αparticle yields. A study of the E_{x} = 16.1 MeV state in (2016HE05) found E_{res} = 150.0 ± 0.5 keV and Γ = 5.0 ± 0.8 keV. See related discussion in (1990BR12, 1996RE16, 1999AN35, 2000LI06, 2012CO19, 2012MI24, 2014DU09). In (2012DI19, 2012FY01), a kinematic energy reconstruction of the 3α energy was used to study αunbound states populated in the γdecay of ^{12}C*(16.1, 16.57). Capture reactions with E_{p} = 165 keV and 350 keV beams populated the higherstates, while ^{12}C*(9.63, 10.8, 12.7) were observed in the lowenergy region of the 3α spectrum. In (2012DI19), the E_{x} = 11.512 MeV region shows evidence for a state that may be associated with J^{π} = 2^{+} strength. An update of this work, (2016LA27) observed evidence for ^{12}C*(16.1) decay to ^{12}C*(10.8) with Γ_{γ} = 0.48 ± 0.04 (stat.) ± 0.11 (sys.) eV; in that work, they gave an overview of the partial decay widths for ^{12}C*(16.1). At E_{p} = 0.675, 1388, 2626 keV (E_{x} = 16.58, 17.23, 18.37 MeV), the relative intensities of the capture γ rays to ^{12}C*(0, 4.44, 7.65, 9.64, 12.71, 15.11) were measured at θ_{lab} = 55° (1990ZI02). See also (1992HO11). In the range 4 < E_{p} < 14.5 MeV, σ(γ_{0}) is dominated by the giant dipole resonance at E_{p} = 7.2 MeV (E_{x} = 22.6 MeV, Γ_{cm} = 3.2 MeV), while the giant resonance in γ_{1} occurs at E_{p} ≈ 10.3 MeV (E_{x} = 25.4 MeV, Γ_{cm} ≈ 6.5 MeV): see (1964AL20). Absolute crosssection measurements from E_{p} = 5 to 14 MeV suggest that dσ/dΩ(90°) = 13.1 ± 1.3 μb/sr be used as a standard at the E_{p} = 7.25 MeV peak of the GDR (1982CO11; also derived σ(E2) for E_{p} = 7 to 14 MeV). The E2 strength is found to be centered near E_{p} = 12 MeV: it exhausts ≳ 30% of the isoscalar E2 sum rule (1976MAZG, 1976MAZL). A study of the giant dipole resonance region with polarized protons (E_{pol. p} = 6 to 14 MeV) sets limits on the configuration mixing in the γ_{0} giant resonance (1972GL01). The analysis of γ_{1} is more complicated: the asymmetry results are constant either with a single J^{π} = 2^{} state or with interference of pairs of states such as (1^{}, 3^{}), (2^{}, 3^{}) and (1^{}, 2^{}) (1972GL01). The 90° yield of γ_{0}, γ_{1}, γ_{2} and γ_{3} [to ^{12}C*(0, 4.4, 7.7, 9.6)] has been studied by (1977SN01): the γ_{2} yield shows a peak at E_{p} ≈ 14.3 MeV with a cross section ≈ 2.3% that of γ_{0} [in γ_{0} yield, E_{res} = 15.0 MeV (1977SN01)] and perhaps a lowintensity structure at E_{p} = 11.8 MeV as well. The γ_{3} yield exhibits two asymmetric peaks at E_{p} = 12.5 and 13.8 MeV (Γ ≈ 0.7 and 2.5 MeV) and a weaker structure at ≈ 9.8 MeV (1977SN01). Resonances populated with E_{p} = 7 to 24.5 MeV beams were studied via γγ techniques by measuring the cascades feeding into the ^{12}C*(15.1) state. In (2008CH13) peaks were found in the excitation function corresponding to E1 transitions from E_{x} = 24.41 ± 0.15 and 28.81 ± 0.10 MeV with Γ_{cm} = 1.3 ± 0.3 MeV and 2.0 ± 0.2 MeV, and (2J + 1) Γ_{p0}Γ_{γ}/Γ = 20.8 ± 2.8 and 150 ± 18 eV, respectively. The peaks were found on a smooth excitation function that had previously been analyzed in (2004CH06). (1983AN09, 1983AN16) have measured the cross sections for γ_{0} and γ_{1} for E_{p} = 18 to 43 MeV. They report giant resonances based on various excited states of ^{12}C at E_{x} = 22.5 and 25.5 MeV (γ_{0}), 25.5, 27.4 and (31) MeV (γ_{1}), 27.4, 31 and (37) MeV (γ_{3}), as well as in the γyield to higher states. At E_{p} = 40, 60 and 80 MeV, radiative capture is observed to a state, or a narrow group of states, at E_{x} = 19.2 ± 0.6 MeV (1979KO05); see also (1982WE08). At E_{pol. p} = 50 MeV, angular distributions and analyzing power measurements are reported to ^{12}C*(0, 4.4, 9.6, 18.8 ± 0.5 [u], 22.3 ± 1.0 [u]) by (1985NO01) [u = unresolved]. At E_{p} = 98 MeV, radiative capture to ^{12}C*(0,4.4, 7.6, 9.6, 12.7, 15.1, 16.1 + 16.6, ≈ 19) (1990HO23, 1992HO04, 1996BR20: E_{p} = 98 and 176 MeV) and internal pair production to ^{12}C*(0, 4.4, 9.64) (1993HO07, 1997TR01) are studied to gain insight into exchange current effects. See also (2000LI06). See other measurements in (1991CA25: E_{p} = 14.24 MeV, 1992KE03: E_{p} = 7 MeV, 1998MA85: E_{p} = 7.2 MeV). (b) In (1993HO07, 1997TR01) radiative capture at E_{p} = 98 MeV followed by decay via internal pair conversion to ^{12}C*(0, 4.4, 9.64) was measured; the internal conversion cross section was roughly two times larger than expected. At E_{p} = 1.6 MeV, the pair decay of ^{12}C*(17.2) was studied (1996DE51) in a search for evidence of a massive neutral boson. See also (1994VA17). (c) Excitation functions have been measured for E_{p} = 0.15 to 18.9 MeV (see 1975AJ02), 35.4 keV to 18 MeV (see 1980AJ01), 4.5 to 24 MeV (see 1985AJ01). Also see references listed below and in the comments of 12.19 (in PDF or PS), 12.20 (in PDF or PS) and 12.21 (in PDF or PS). Astrophysically relevant ^{11}B(p, α) cross sections were measured in (1993AN06: E_{p} = 17 to 134 keV); see additional comments on electron screening in (1993AN06, 1997BA95, 2002HA51, 2002BA77) and other discussions in (1995YA07, 1996RA14, 2004RO27, 2004SP03, 2008LA18, 2010LA11, 2011ST01, 2012CO19, 2013KI06). The use of this reaction for clean fusion energy generation is discussed in (1996YU04: E_{p} = 0.165 to 2.58 MeV, 1998LI51: E_{p} = 667 and 1370 keV, 1999LI13, 2015BE28). Surface analysis techniques and related cross sections are given in (1991BA61: E_{p} = 660 keV, 1992LA08: E_{p} = 650 keV, 1996VO23: E_{p} = 160 to 800 keV, 1998MA54: E_{p} = 1.7 to 2.7 MeV, 2002LI29: E_{p} = 0.4 to 1.6 MeV, 2010KO33: E_{p} = 2.2 to 4.2 MeV). See additional theoretical analysis in (1992KO26, 1994SH21, 2006DM01). The total cross section shows the 162 keV resonance and a broad peak centered at 600 keV. At E_{cm} = 300 keV σ(α_{0}) = 1.03 ± 0.06 mb and σ(α_{1}) = 165 ± 10 mb (1987BE17). The parameters of the 162 keV resonance are E_{res}(cm) = 148.3 ± 0.1 keV, Γ_{cm} = 5.3 ± 0.2 keV (1987BE17), 149.8 ± 0.2 keV, 5.2^{+0.5}_{0.3} keV (1979DA03). Derived Svalues lead to S(0) = 197 ± 12 MeV ⋅ b (1987BE17). The reaction proceeding via 3α breakup into the 3body continuum is of astrophysical importance; however the reaction proceeds predominantly by sequential twobody decays via ^{8}Be*(0, 2.9). In past reviews, the reactions ^{11}B(p, α)^{8}Be and ^{11}B(p, α)^{4}He^{4}He were distinct in that experiments grouped with the later reaction detected both α particles from the decay of ^{8}Be. In (2016LA27) the 3body decay of ^{12}C*(16.11) was analyzed using Dalitz plots, which indicated primarily sequential decay. Analysis of the multiplicity = 2α and 3α events yields Γ_{α0}/Γ = 0.054 ± 0.011 and 0.051 ± 0.005 respectively. The text includes discussion on the "ghost" of the ground state; it is suggested that a correction for the "ghost" could raise the Γ_{α0}/Γ value by ≈ 25% to around 0.065, as in (2012AL22). Beams of E_{p} = 0.675 and 2.64 MeV protons were used to study the decay mechanisms of ^{12}C*(16.576, 18.38) (2011ST01); the decays were found to proceed primarily via l = 3 and 1 α_{1} emission, respectively. At higher energies, resonances are observed at E_{p} = 4.68, 5.10, 6.08, 6.58 and 7.11 MeV [E_{x} = 20.25 to 22.47 MeV] (1983BO19) and some broad structures are reported by (1983BU06). Contributions from ^{12}C*(23.0, 23.6, 25.4) are reported in (1975VA04). A wide resonancelike structure centered at E_{p} = 13 MeV [^{12}C*(28)] with Γ ≈ 6 MeV is reported by (1977BU07): the angular distributions of α_{0} show prominent backward peaking. No marked structure is observed above E_{x} = 28 MeV (1972TH1C: Ph.D. thesis). The parameters of the observed resonances are displayed in 12.19 (in PDF or PS) and 12.20 (in PDF or PS). The following summarizes the information on the lowlying resonances: for a full list of references see (1968AJ02, 1980AJ01). E_{p} = 0.16 MeV [^{12}C*(16.11)]. This is the J^{π} = 2^{+}; T = 1 analog of the first excited states of ^{12}B and ^{12}N. The γdecay is to ^{12}C*(0, 4.4, 9.6): the angular distribution of γ_{3}, together with the known αdecay of ^{12}C*(9.6), fix J^{π} = 3^{} for the latter (1961CA13). E_{p} = 0.67 MeV [^{12}C*(16.58)]. The proton width [Γ_{p} ≈ 150 keV] indicates swave protons and therefore J^{π} = 1^{} or 2^{}. This is supported by the near isotropy of the two resonant exit channels, α_{1} and γ_{1}. The α_{1} cross section indicates 2J + 1 ≥ 5: therefore J^{π} = 2^{}. [This is consistent with the results of an αα correlation study via ^{8}Be*(2.9) (1972TR07)]. The γ_{1} E1 transition has M^{2} ≈ 0.01 W.u., suggesting T = 1 (1957DE11, 1965SE06). (1962BL10) report a γ branch to ^{12}C*(12.71) (≈ 6% of the intensity of the γ_{1} transition). Such a branch may also be present for ^{12}C*(17.23). E_{p} = 1.4 MeV [^{12}C*(17.23)]. (2J + 1) Γ_{γ0} ≥ 115 eV. This indicates J^{π} = 1^{}, with T = 1 most probable (1965SE06). J^{π} = 1^{} is also required to account for the interference at lower energies in α_{0} and γ_{0}: see (1957DE11) and is consistent with the αα correlation results of (1972TR07). Two solutions for Γ_{p} are possible; the larger (chosen for 12.19 (in PDF or PS) and 12.20 (in PDF or PS)) is favored by elastic scattering data (1965SE06). E_{p} = 2.0 MeV [^{12}C*(17.76)]. The resonance in the yield of α_{0} requires natural parity, the small αwidths suggest T = 1. For J^{π} = 1^{} or 3^{} the small γwidths would be surprising; J^{π} = 2^{+} would lead to a larger anomaly than is observed. J^{π} is then 0^{+}; T = 1 (1965SE06). A study of E_{p} = 0.82 to 2.83 MeV reports that E_{x} = 17.80 MeV [Γ_{cm} = 96 ± 5 keV] decays via a 5.10 ± 0.03 MeV γray to ^{12}C*(12.71): Γ_{γ} = 3.7 ± 1.5 eV. The angular distribution is isotropic, as expected (1982HA12). E_{p} = 2.37 MeV [^{12}C*(18.13)]. Seen as a resonance in the yield of 15.1 MeV γrays: σ_{R} = 0.77 ± 0.15 μb, Γ_{cm} = 600 ± 100 keV, (2J + 1) Γ_{γ} ≥ 2.8 ± 0.6 eV. The results are consistent with J^{π} = 1^{+}; T = 0, but interference with a nonresonant background excludes a definite assignment (1972SU08). E_{p} = 2.64 MeV [^{12}C*(18.38)]. The resonance for α_{0} requires natural parity; the presence of a large P_{4} term in the angular distribution requires J ≥ 2 and l_{p} ≥ 2. The assignment J^{π} = 3^{} is consistent with the data (1965SE06, 1972CH35, 1972VO01, 1974GO21). (1982HA12) report E_{x} = 18.38 MeV, Γ_{cm} ≈ 400 keV, Γ_{γ} (to ^{12}C*(9.6)) = 5.7 ± 2.3 eV, consistent with J^{π} = 3^{}; T = 1. The total peak cross section is 4.2 ± 1.7 μb. Transitions to ^{12}C*(0, 4.4) are also observed: Γ_{γ} ≈ 2 × 10^{3} eV and 3.2 ± 1.0 eV, respectively. E_{p} = 2.66 MeV [^{12}C*(18.40)] is not observed in these reactions: see ^{11}B(p, p). E_{p} = 3.12 MeV [^{12}C*(18.80)]. The angular distribution of γ_{0} indicates E2 radiation, J^{π} = 2^{+}. This assignment is supported by the angular correlation in the cascade γ_{1} and by the behavior of σ(α_{0}); T = 1 is suggested by the small Γ_{α} (1965SE06). The yield of γ_{3} (to ^{12}C*(9.6)) shows a peak corresponding to E_{x} ≈ 18.9 to 19.0 MeV. It may be due to ^{12}C*(18.8) with an energy shift due to interference (1982WR01). The structure near E_{p} = 3.5 to 3.7 MeV [^{12}C*(19.2, 19.4)] seems to require at least two levels. The large Γ_{γ0} requires that one be J^{π} = 1^{}; T = 1 and interference terms in σ(α_{0}) require the other to have even spin and even parity: J^{π} = 2^{+}; T = 0 is favored (1963SY01, 1965SE06). (1982WR01) do not observe any evidence for an isospin mixed doublet near E_{x} = 19.5 MeV [E_{p} = 2.9 to 4.6 MeV (60° and 90°)]. Levels at E_{p} = 4.93 and 5.11 MeV, seen in σ(γ_{1}) (1955BA22) also appear in σ(α_{1}), but not in σ(α_{0}). Angular distributions suggest J^{π} = 2^{+} or 3^{} for the latter [^{12}C*(20.64)]; the strength of γ_{1} and absence of γ_{0} favors J^{π} = 3^{}; T = 1 (1963SY01, 1965SE06). The first seven T = 1 states in ^{12}B and ^{12}C have been identified by comparing reduced proton widths obtained from this reaction and reduced widths obtained from the (d, p) and (d, n) reactions: see 12.12 (in PDF or PS) of (1980AJ01) and (1971MO14, 1974AN19).
Excitation functions have been studied at E_{p} = 2 to 5, 2.6 to 5.5, 3 to 4, 4 to 11.5, 4 to 14 and 4.9 to 11.4 MeV [see (1968AJ02)], from threshold to 6.0, 5.4 to 7.5 and 10.87 to 27.50 MeV [see (1985AJ01)], E_{p} = 13.7 to 14.7 and 16 to 26 MeV [see (1990AJ01)]. At the higher energies the excitation function decreases essentially monotonically (1981AN16). At the lower energies many peaks are observed whose positions correspond with structures seen in ^{11}B(p, γ)^{12}C and ^{11}B(p, α)^{8}Be and ^{12}C(γ, n) and ^{12}C(γ, p) reactions, suggesting that resonances, and not fluctuations, are involved; see 12.21 (in PDF or PS). Angular distributions do not change as rapidly as might be expected from the pronounced structures in the excitation function (1965OV01). The strength of the pronounced peak at E_{p} = 6.03 MeV (E_{x} = 21.49 MeV) appears to demand J ≥ 4 (1961LE11). See also (1994SH21, 1995SH44, 1999AN35, 2009EL09). Polarization measurements have been carried out for E_{pol. p} = 186 MeV (1994RA23, 1994WA22, 1995YA12) and 295 MeV (1995WA16) and at E_{pol. p} = 7.0 to 26.5 MeV [see articles cited in (1975AJ02, 1980AJ01, 1985AJ01)]. For highenergy interactions see (1994GA40, 1994GA49) and work cited in (1990AJ01).
States shown in 12.21 (in PDF or PS) are revealed in the excitation functions, which have been studied at E_{p} = 0.3 to 1.0, 0.6 to 2.0, 2 to 5.3 MeV [see (1959AJ76)], E_{p} = 0.5 to 4.0, 1.8 to 4.1 MeV [see (1968AJ02)], E_{p} = 1.9 to 3.0, 3.5 to 10.5, 7.5 to 21.5 MeV [see (1975AJ02)], E_{p} = 1.8 to 3.1, 1.9 to 3.0, 3.0 to 5.2, 3 to 8, 7.5 to 10.5 and 19.2 to 47.4 MeV [see (1980AJ01)], E_{p} = 4.5 to 7.5, and 5.4 to 7.0 MeV [see (1985AJ01)], and E_{cm} ≈ 0.15 to 1.1 MeV (1990AJ01), E_{p} = 0.3 to 1.05 MeV (2011AM02), 0.5 to 3.3 MeV (2001CH78), 1.7 to 2.7 MeV (1998MA54), 2.2 to 4.2 MeV (2010KO33). No pronounced structure is observed above E_{x} = 28 MeV (1969TH1B, 1971TH1F, 1972TH1C). It is reported that in all the channels and throughout this energy range a strong 2^{+} background is observed. It is suggested that it may be the lowenergy tail of the isoscalar giant quadrupole resonance (1983BO19). Polarization measurements are reported in (1975AJ02, 1980AJ01, 1990AJ01) and in (2003HA11, 2003HA12, 2004KA53). For studies of highenergy interactions see (2004KA53, 2004KA56). Applied uses of this reaction are discussed in (1990BO15, 1994MI21, 1998MA54, 2010KO33) Also see (1994SH21, 1998DO16, 2013HA17).
At E_{pol. p} = 11.34 to 11.94 MeV the VAP angular distributions and excitation functions of the deuterons have been studied by (1982BU03). See also (1991AB04, 1994SH21).
Angular distributions of the neutrons to many ^{12}C states up to E_{x} = 17.23 MeV have been reported (see 12.22 (in PDF or PS)) for energies in the range E_{d} = 0.5 to 10 MeV [see (1968AJ02)], E_{d} = 2.5 to 4 MeV (1972ME06), E_{d} = 5.5, 6 and 11.8 MeV [see (1975AJ02)], E_{d} = 0.9 and 1.2 MeV (1975SI22), E_{d} = 7 to 16 MeV (1981AN16), E_{d} = 12 MeV (1983NE11), E_{pol. d} = 79 MeV (1985FO05, 1987FO22), and E_{d} = 111 keV (2001HO23), E_{d} = 120 to 160 keV (2006PA27) and E_{d} < 5 MeV (2013CO12). Proton and αdecay from excited states are reported in (1965OL01, 1985NE01). J^{π} = 3^{} for the 9.64 MeV state is favored on the basis of the angular distribution of the αparticles to ^{8}Be_{g.s.}. There is no evidence for direct 3αdecay of ^{12}C levels in the range E_{x} = 9 to 13 MeV, nor does ^{12}C*(10.3) appear to participate in this reaction (1965OL01). Relative spectroscopic factors obtained in several (d, n) and (^{3}He, d) studies are summarized in (1975AJ02), but see (1971MU18) for a discussion of the problems involved in comparing spectroscopic factors obtained in these different reactions. See a comparison of cross section calculations from the TALYS nuclear reaction code with reaction rates from the NACRE data base in (2012CO01). Angular correlations of neutrons and 4.4 MeV γrays and neutrons and 15.1 MeV γrays are reported in (1968AJ02, 1975AJ02). For polarization measurements see references in (1990AJ01).
Observed deuteron groups are displayed in 12.22 (in PDF or PS). Also see 12.17 (in PDF or PS), which has results from ^{10}B(^{3}He, p3α) and ^{11}B(^{3}He, d3α) complete kinematics studies given in (2007BO49, 2009KI13, 2010KI08, 2011AL28, 2012AL22, 2012KI07, 2013KI07). Angular distributions have been measured at E(^{3}He) = 5.1 to 44 MeV [see (1968AJ02)], 10, 11, 12, 18 and 44 MeV [see (1975AJ02)], 23.2 MeV [see (1980AJ01)], 43.6 MeV [see (1985AJ01)], 18.3 and 22.3 MeV [see (1990AJ01)] and 44 MeV (2012SM06). The angular distributions exhibit characteristic direct interaction features (1967CR04). A J^{π} = 2^{+} state at E_{x} = 11.16 was reported at E(^{3}He) = 44 MeV in (1971RE03): the group appeared as an enhancement on the high energy side of the E_{x} = 10.84 MeV peak; however a study under the same kinematic conditions found no evidence for such a peak (2012SM06). The Rmatrix analysis of (2012SM06) showed that the fit to their data was improved by including a J^{π} = 2^{+} resonance at E_{x} = 9.7 MeV: note there is no visible peak in the spectrum at this energy. At E(^{3}He) = 22.3 MeV, spectroscopic factors of S = 1.6 and 0.33 are deduced for ^{12}C*(0,4.4), respectively (1993AR14); See 12.14 (in PDF or PS) in (1980AJ01) for earlier reported values and see (2010TI04, 2016CO14). The d_{1}γ angular correlations are studied in (1988IG03).
Angular distributions of t_{03} and to ^{12}C*(12.7) have been measured at several energy between E_{α} = 15.1 to 120 MeV [see references in (1968AJ02, 1975AJ02, 1980AJ01, 1985AJ01 1990AJ01)]. Singleproton transfer seems to be the dominant reaction mode (1967DE1K). Angular correlation measurements of t_{1}γ are reported at E_{α} = 21 to 30 MeV: see (1972EL09, 1987VA04, 1988IG04). See also reaction mechanism studies in (1989BA86, 1990BO23, 1990BA62, 1991BA23, 1998GA46, 1999GA43, 1999LE48).
At E(^{7}Li) = 18.3 and 28.3 MeV, angular distributions to ^{12}C_{g.s.} were measured and analyzed via DWBA to determine the ^{6}He + ^{12}C and ^{7}Li + ^{11}B optical Model parameters (2009WU01). At E(^{7}Li) = 34 MeV, angular distributions have been measured and spectroscopic factors deduced for the groups to ^{12}C*(0, 4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 15.1, 16.1, 18.35) (1983NE11, 1987CO16). It is concluded on the basis of these and other works, that the group corresponding to E_{x} = 18.35 ± 0.05 MeV (Γ = 350 ± 50 keV) consists of unresolved ^{12}C states with J^{π} = 3^{} (T = 1) and 2^{} (T = 0 plus some mixing of T = 1). No states were observed with E_{x} > 18.35 MeV.
Angular distributions involving ^{12}C*(0, 4.4) and ^{10}Be*(0, 3.4) have been measured at E(^{11}B) = 11 MeV (1985PO02).
The ^{13}N valence proton wave function was evaluated using the (^{13}N, ^{12}C) reaction on ^{11}B at E(^{13}N) = 29.5 and 45 MeV (1998DI14). States at ^{12}C*(0, 4.44, 15.1) are found to participate, along with 3α unbound states. Further studies on ^{24}Mg states, some of which are found to possess significant components of 3^{}_{1} + 3^{}_{1}, 3^{}_{1} + 1^{}_{1} and 0^{+}_{2} + 3^{}_{1}, are given in (1999DI04, 2001DI12).
Angular distributions to ^{12}C_{g.s.} were measured at E(^{14}N) = 41, 77 and 113 MeV (1971LI11) and optical model parameters were deduced. For reaction (b), angular distributions to ^{12}C*(0, 4.44, 9.6) have been measured at E(^{16}O) = 27, 30, 32.5, 35 and 60 MeV (1972SC03): at the highest energy the ratio of relative spectroscopic factors, θ^{2}/θ^{2}_{g.s.}, for the transitions ^{11}B_{g.s.} + p → ^{12}C* is 0.12 and 0.05, respectively, for ^{12}C*(4.4, 9.6). See (1975SC35) for analysis of reactions to the ground state at E(^{16}O) = 27 to 35 MeV, and see (1992KA19) for analysis of multicluster transfer processes in the reaction.
The impact of reactions such as ^{11}C(n, γ), ^{11}C(n, α) and ^{11}C(d, p) on nucleosynthesis is analyzed (2012CO01).
^{12}B decay to ^{12}C is complex. Most of the decay populates ^{12}C_{g.s.} with small branches populating ^{12}C*(4.4) and several αparticle unbound states (see 12.24 (in PDF or PS)). See general discussion in (1992BA11, 1993CH06). The ground state decay branch is determined by subtracting all other observed decay branches from unity. Early studies were motivated by evaluation of the ^{12}B and ^{12}N mirror decays to states in ^{12}C and by parity violation studies. The decay rates to ^{12}C*(4.4) measured in (1981KA31) are deduced while taking significant care to decrease systematic effects that could distort the results; they are the most precise and have been used as normalization factors in modern experiments to deduce the relative and absolute branching ratios of weaker decay branches. We adopt the branching ratios of (1981KA31) to ^{12}C*(4.4). Significant efforts have focused mainly on the ratio of the βdecay branches of ^{12}B and ^{12}N to ^{12}C*(4.4) and the relevance of mirror asymmetries in βdecay; see 12.23 (in PDF or PS). In the case of ^{12}N, the measurement is complicated because the highenergy 17.3 MeV β^{+} particles can produce Bremsstrahlung photons and give rise to a huge background. A lower Qvalue in the case of ^{12}B β^{}decay makes these measurements less complicated. Discussion on systematic effects in the measurements is given in (1974MC11, 1978AL01). In (1963PE10, 1963WI05) the experimental layout used a scintillator βcounter that covered only part of the total solid angle along with NaI detectors; the βγ coincidence data were analyzed. Other experimental efforts surrounded the targets with welltype scintillators while also detecting γrays in a NaI detector and analyzing the βγ coincidence events (1972AL31, 1974MC11). The use of Ge(Li) and HPGe detectors significantly improved results from the measurements reported in (1978AL01, 1981KA31, 1988NA09). In most cases, the ratio of ^{12}Bto^{12}N βγ(4.44) coincidences was measured by using an essentially identical configuration for the two decays; then in some cases the configuration was modified to permit an absolute measurement of the ^{12}B decay branch to ^{12}C*(4.4) (1978AL01). In (1963PE10, 1981KA31) absolute ^{12}N decay intensities were measured along with the mirror decay ratio. In the early study of (1957CO59) βdelayed α particles were studied in an effort to validate the prediction of a narrow "3α" state located just above the breakup threshold. The Hoyle state was reported in ^{12}B decay with the branching ratio (1.3 ± 0.4)%, J^{π} = 0^{+} and Q(^{12}C^{8}Beα) = 278 ± 4 keV (E_{x} = 7.65 MeV). Analysis of a higher energy α group (1958CO66) was consistent with a broad J^{π} = 0^{+} (or 2^{+}) state near 10.1 MeV with a (0.13 ± 0.04)% branching ratio. Later, in (1963WI05) the α, β and γ products were measured and analyzed for evidence of states in the E_{x} = 9 to 12 MeV region; their best fit included states at E_{x} = 10.1 and ≈ 11.8 MeV. It is later pointed out in (1967AL03, 2009HY02) that the early works such as (1958CO66, 1963WI05) assigned too much intensity to the E_{x} = 10.3 MeV strength because they were unaware of the presence of the E_{x} = 12.71 MeV state. The work of (1966SC23) found evidence for ^{12}C*(10.3 ± 0.3) decaying primarily to ^{8}Be_{g.s.} + α_{0} with a likely J^{π} = 0^{+} and for ^{12}C*(12.71) decaying > 96% to ^{8}Be*(2^{+}) + α, hence J^{π} = 1^{+}. The relative ratio of I_{β}(10.3)/I_{β}(12.7) was found as 0.20 ± 0.05. On the other hand, the studies of (1962MA22, 1963GL04) used magnetic spectrometers to measure the β^{∓}particle energy spectra. While the main thrust of these measurements focused on the energy dependence of the shape factors, results on intensities to ^{12}C*(7.65, 10.3) were also obtained in the analysis. See also (2015MO10). In (1963AL15), the γ_{3.23}γ_{4.44} sequential deexcitation γ rays from ^{12}C*(7.65) and the βγ_{3.23}γ_{4.44} events are analyzed to determine Γ_{γ}/Γ(7.65) = (3.8 ± 1.5) × 10^{4} and the (1.7 ± 0.5)% for the ^{12}B βdecay branching ratio to ^{12}C*(7.65). A similar measurement was carried out using the Gammasphere array (2016MU06); in that work (0.64 ± 11)% is determined for the βdecay branching ratio to ^{12}C*(7.65) and E_{γ} = 3216.9 ± 0.4 (stat.) ± 0.7 (sys.) keV and 4439.5 ± 0.7 (sys.) keV are determined for the transitions between the J^{π} = 0^{+}_{2} → 2^{+}_{1} and J^{π} = 2^{+}_{1} → 0^{+}_{1} states. This corresponds to E_{x} = 7657.8 ± 1.0 keV, which is in poor agreement with the adopted value in 12.13 (in PDF or PS), E_{x} = 7654.07 ± 0.19 keV (1976NO02). In 12.24 (in PDF or PS) it is highlighted that some of the differences in published branching ratios are connected with the use of updated values in their computations. In (1973BA73) the energy of the Hoyle state was determined by implanting ^{12}B activity, produced via the ^{11}B(d, ^{12}B) reaction, into a thick Si detector and measuring the 3α breakup energy, Q = 379.6 ± 2.0 keV. Prior to development of rare isotope facilities, the ^{12}B and ^{12}N activities were typically produced in the target using the ^{11}B(d, n) and ^{10}B(^{3}He, n) reactions, respectively. These approaches have the disadvantage of producing unwanted activities such as ^{11}C, ^{13}N and ^{14}O in the targets. Renewed interest in the higherlying J^{π} = 0^{+} and 2^{+} states led to measurements where ^{12}B and ^{12}N were produced at rare isotope facilities. An early series of experiments (2002FY02, 2003FY02, 2003FY04, 2004BO43, 2004FY02, 2004FY03) focused on identifying ^{12}C*(10.3) → ^{8}Be_{g.s.} + α and ^{12}C*(12.71) → ^{8}Be*(2^{+}) + α_{1} as the dominant breakup mechanisms for these states by analyzing the αparticle correlations. These data also gave indications of important interference effects between the E_{x} = 7.65 and 10.3 MeV J^{π} = 0^{+} states, as had been suggested in (1963WI05). In follow up measurements, two different experimental approaches enhanced the available data (2005DI16, 2009DI06, 2009HY01, 2009HY02, 2014TE01); in one case the ions were implanted into a thin carbon foil and the full decay kinematics of breakup αparticles was measured. Analysis yielded the decay intensity of ^{12}C excited states along with an assessment of the decay mechanism. In the second approach, ions were implanted in a segmented strip detector whose thickness stopped the full decay energy of breakup αparticles; this calorimeter approach provided a measure of the energies populated in ^{12}C with fewer systematic effects than prior experiments. The general shapes of spectra observed in (2009HY01, 2009HY02) were found in reasonable agreement with prior results. Implementation of HPGe detectors in the setups of (2009HY01, 2009HY02) permitted a simultaneous and absolute normalization of the β branching ratios to all unbound states using the known branching ratio to the ^{12}C*(4.44) state. In this case, the total intensities of ^{12}C*(12.71, 15.11) must be adjusted to account for the Γ_{γ} decay branches. See 12.24 (in PDF or PS). The work of (2009HY01, 2009HY02, 2010HY01) focused on a search for unknown and unresolved J^{π} = 0^{+} and 2^{+} strength in the E_{x} = 916 MeV region. Their analysis found that interference of the J^{π} = 0^{+}_{2} state with other J^{π} = 0^{+} strength around E_{x} ≈ 11.2 MeV leads to "the very broad component from 8.5 to 11 MeV, which has been mistaken for a 10.3MeV resonance with a 3MeV width". Rather than attribute their observed strength to a 10.3 MeV group, they provided the β feeding strength for the E_{x} = 912 MeV and 1216.3 MeV regions [excluding the 12.7 MeV state]. In (2010HY01), a multilevel manychannel Rmatrix analysis of the data was carried out. The data was best fit with a J^{π} = 0^{+} state at E_{x} = 11.2 ± 0.3 MeV with Γ = 1.5 ± 0.6 MeV and B(GT) = 0.06 ± 0.02 and a J^{π} = 2^{+} state at E_{x} = 11.1 ± 0.3 MeV with Γ = 1.4 ± 0.4 MeV and B(GT) = 0.05 ± 0.03.
Violation of the Pauli exclusion principle could permit ^{12}C to decay by converting a pshell nucleon into as 1s_{1/2}shell nucleon followed by emission of a ≈ 20 MeV γ ray. The reaction has not been observed. The limit on the mean lifetime of ^{12}C for this decay is τ_{m} ≥ 5.0 × 10^{31} yr (2010BE08); see also (1979LO13, 1998BA57, 1999AR22). Lifetimes for other ^{12}C_{g.s.} exotic decays are > 8.9 × 10^{29} yr (2010BE08); see also (2003BA42).
The total absorption, mainly (γ, n) + (γ, p), is dominated by a giant resonance peak at E_{x} = 23.2 MeV, Γ = 3.2 MeV [σ_{max} = 21 mb] and by a smaller structure at E_{x} = 25.6 MeV, Γ ≈ 2 MeV [σ_{max} ≈ 13 mb]: see (1975AH06) and references tabulated in (1968AJ02, 1975AJ02). The (γ, n) cross section shows a giant resonance, σ_{max} ≈ 7  8 mb, centered at about 23 MeV and consisting of an ≈ 1 MeVwide group at 22.3 MeV and an ≈ 2 MeVwide group at ≈ 23.3 MeV. A secondary maximum occurs at 25.5 MeV, Γ ≈ 2 MeV with evidence for other structures at ≈ 30  31 and possibly at ≈ 35 MeV (1966FU02, 1966LO04); see also (1999AB39, 1999AB40, 2000AB35: E_{brem} = 20 MeV), (2003CH80, 2016HE07) and the atlas of photoneutron cross sections (1988DI02). The (γ, n_{0}) cross section has been measured at θ = 90° for 21 < E_{x} < 40 MeV and compared with the (γ, p_{0}) cross section (1968WU01): the isospin mixing averages about 2% in intensity and shows structure at the giant resonance. Angular distributions of n_{0} measured over the giant resonance region indicate that the main excitation mechanism is of a 1p_{3/2} → d_{5/2} E1 singleparticle character. No significant E2 strength is observed (1968RA21). At E_{γ} = 60 MeV a comparison of the (γ, n_{0}) and (γ, p_{0}) cross sections indicates the reaction mechanism is absorption and suggests the reaction is useful for studying correlated np pairs (1980GO13). A comparison of the ^{12}C(γ, p)^{3}H2α and ^{12}C(γ, n)^{3}He2α reactions at E_{γ} = 30 to 120 MeV is given in (2007AF02). See also results in (1993AN17: E_{brem} = 58 MeV), (2001KO62: E_{brem} = 70 to 140 MeV) and (1994RY03, 2000LE38, 2003VA20, 2011DZ02). The (γ, 2n) cross section (reaction (b)) is much smaller than that for (γ, n): the highest value is 0.15% of the maximum value for reaction (a) in the energy range E_{γ} = 20 to 140 MeV (1970KA37). The reaction has been studied for E_{brem} = 100 to 800 MeV with an emphasis on ^{11}C production (1977JO02): see other references in (1975AJ02, 1980AJ01, 1985AJ01, 1990AJ01).
The photoproton cross section exhibits two broad peaks, the giant resonance peak at 22.5 MeV, Γ = 3.2 MeV, σ_{max} = 13.1 ± 0.8 mb and a 2 MeV broad peak at 25.2 MeV, σ_{max} = 5.6 ± 0.3 mb: see (1976CA21) and values listed in 12.19 (in PDF or PS) in (1968AJ02). The (γ, p_{0}) cross section at the giant resonance is 11.0 ± 1.1 mb (1986KE06). While the E1 component dominates in the GDR, a 2% E2 contribution may be present (1976CA21). In contrast with the giant resonance peak in the (γ, n) cross section, the (γ, p) cross section shows a sharp peak in the center of the broad giant resonance peak. See also (1991IS09). Above 24.5 MeV the ground state (γ, p) and (γ, n) excitation functions have the same shape up to at least 36 MeV: see (1985FU1C). The (γ, p) results of (1968FR12, 1968FR14, 1969CA22) are in good agreement with those of (1964AL20) for the inverse reaction, ^{11}B(p, γ_{0})^{12}C [see reaction 20], when the population of ^{11}B*(4.4, 5.0) is taken into account: the required cross sections for the (γ, p_{2}) and (γ, p_{3}) processes peak at 1.5 mb at 29 and 30 MeV, respectively (1973DI1C, 1974DI17). The population of ^{11}B states has been determined at various energies. The ground state is predominantly populated in these reactions; see measurements and discussion in (1980AJ01, 1985AJ01, 1990AJ01) and (1986AN25, 1986MC15, 1990SP06, 1990VA07, 1990VA09, 1991IS09, 1993IR01, 1994NI04, 1994ZO01, 1995HA03, 1995MO18, 1996KU36, 1996RU15, 1997AS01, 1997ZO02, 1998KU23, 1998SO18, 2001ME29, 2006MO11). Nuclear transparency, as well as the roles of different reaction mechanisms, including quasideuteron knockout, are investigated in (1990VA07, 1992RY02, 1992VA01, 1993HA12, 1993IR01, 1994IR01, 1994NI04, 1994RY03, 1995MO18, 1996AS02, 1996JO15, 1996RU15, 1997AS01, 1997BO22, 1997JO07, 2000LE38, 2002ME17, 2005GL05, 2005KA54, 2006CO19, 2013RO17). Reactions in the Δ resonance region are discussed in (1992BA57, 1992GL04, 1995CR04, 1997JO07, 1997LI30, 1998GL14, 1999FI01, 2000DE58, 2000GL08, 2001MA31, 2002ME17, 2003GL03, 2006AN22, 2008GL05, 2010GL02, 2012GL02, 2013GL03, 2014GL03). In this region peaks corresponding to the removal of sshell or pshell protons from ^{12}C are observed in the missing mass spectrum, and quasifree photo pion production is an important reaction mechanism. Searches for Δ components in the ^{12}C_{g.s.} are discussed in (2001BY01, 2002BY03). Evidence for ηmesic ^{11}B atoms is claimed in (1999SO18, 2000SO19, 2000YO02, 2002BA21); also see (1995LE26, 1996LE11, 1996RO06, 1997FI07, 1997HE14, 1998AB13, 1998EF09, 1998HE18, 1998PE12, 1999LE35, 1999TR09, 2000EF04, 2001BL13, 2001TR06, 2003HE18, 2003VA08, 2004MA27, 2005MO04, 2005NA17, 2005NA25, 2005NA35, 2006NA34, 2007HE29, 2008JI06, 2008ME15, 2015NE10).
Photopion production has been measured at E_{γ} = 111 to 160 MeV (1997BE22), 120 to 819 MeV (2008TA05), 130 to 165 MeV (1995VO17), 141 to 159 MeV (2008BA24), 170 to 177 MeV (1995GO27, 2008GO20), 200 to 350 MeV (2002KR02), 200 to 800 MeV (1998KR28, 2004KR16), 300 to 400 MeV (1991BE16) and 4.5 GeV (1993EG06). The 2π^{0} correlations were measured at E_{γ} = 200 to 820 MeV (2003ME32) and at 400 to 460 MeV (2002JA10, 2002ME22). General discussion, for example on photopion production in the Δresonance region, can be found in (1991TR02, 1992CA16, 1994BE31, 1994KO23, 1994OS02, 1995BA92, 1995HO12, 1996MA20, 1997EF03, 2000GL08, 2002BA23, 2004MU17, 2006DA17, 2007TR04, 2008CO04). Coherent photopion production is discussed in (1991BO26, 1993CA35, 1993LA07, 1993OL06, 1996TR07, 1997KA65, 1998PE09, 1999AB42, 1999DR17, 2005KR18, 2010NA04, 2012ZH39), and inmedium effects are discussed in (1996OS02, 1999LE35, 2002RO28, 2003RO20, 2003VI09, 2003VI11, 2005KR10, 2005RO13, 2006SC18). For ^{12}C(γ, π^{+}) see ^{12}B reaction 23 and for ^{12}C(γ, π^{}) see ^{12}N reaction 8.
Cross sections and angular distributions of the deuterons corresponding to transitions to ^{10}B_{g.s.} and/or low excited states have been measured at E_{γ} ≈ 40 MeV: the results are consistent with E2 strength. There is some evidence for the excitation of higher states of ^{10}B via nonE2 transitions (1972SK08). For E_{brem} = 90 MeV, the ratio of the yields of deuterons to protons is ≈ 2%, for particle energies 15 to 30 MeV. For higher particle energies, the ratio decreases (1962CH26). The excitation function for deuterons to E_{γ} = 1.4 GeV is given in (1969AN10, 1971AN15, 1972AN09, 1972AN22). The (γ, pn) reaction has been studied at E_{γ} = 83 to 133 MeV by (1988DA16), at E_{brem} = 150 MeV by (1999KH06) and in the Δresonance region by (1987KA13, 1996HA17, 1996LA15, 1998HA01, 1998MA02, 1998YA05, 1999FR32, 2000WA20, 2001PO19); see also (1996OS01, 1998RY01, 1999IR01, 2000GR13, 2003WA01). Momentum spectra for deuterons and tritons (reactions (a) and (c)) are reported at E_{γ} = 300 to 600 MeV by (1986BA07). The yield of tritons has been measured for E_{γ} = 35 to 50 MeV: see (1967KR05) and E_{γ} < 1.2 GeV (1972AN09). For reaction (d) see (1987VO08: E_{brem} = 80 MeV), (1999MC06: E_{brem} = 150 to 400 MeV) and (2007WA12: E_{pol. brem} = 170 to 350 MeV).
A study of the α breakup cross section using quasimonoenergetic and polarized beams with E_{γ} = 9.0 to 10.7 MeV found enhanced E2 strength corresponding to E_{x} = 10.03 ± 0.11 MeV with Γ = 0.80 ± 0.13 MeV and Γ_{γ} = 60 ± 10 meV (2013ZI03); in the analysis the α^{8}Be breakup angular distribution was analyzed to determine the E1/E2 contributions and the mixing phase. This state is interpreted as the J^{π} = 2^{+} excitation of the E_{x} = 7.65 MeV astrophysically important Hoyle state. Also see (2011GA09, 2012GA39), (2016HA05: theory) and (1994OB03, 2011GA47, 2011IS14, 2013IS05, 2014IS06, 2015GA17: astrophys.). At higher energies, the total cross section exhibits broad peaks at E_{x} = 17.47 ± 0.12 MeV with Γ = 6.12 ± 0.14 MeV and 27.12 ± 0.34 MeV with Γ = 4.56 ± 0.14 MeV (2008AF04). A pronounced minimum occurs at 20.5 MeV: to what extent the peaks have fine structure is not clear; see (1964TO1A) and references in (1968AJ02). Alpha energy distributions show surprisingly strong E1 contributions below E_{γ} ≈ 17 MeV (1955GO59, 1964TO1A). For E_{γ} < 22 MeV, transitions are mainly to ^{8}Be_{g.s.} and ^{8}Be*(2.9) with the g.s. transition dominating for E_{γ} ≲ 14 MeV. For E_{γ} > 26.4 MeV, ^{8}Be (T = 1) levels near 17 MeV are strongly excited (1955GO59, 2008AF04). The mechanism for formation of various ^{8}Be excited states up to E_{x} ≈ 23 MeV was carefully studied for photon energies below E_{brem} = 40 MeV (2008AF04), and resonances have been deduced; see 12.25 (in PDF or PS). See also (1992DZ02, 1993KI15, 1997GO16, 1998KO77, 2001KI33, 2002KO65). The ratio for σ(γ, α_{0})/σ(γ, p_{0}) is 0.029 ± 0.012 at E_{γ} = 28 MeV (1989FE01). For other breakup processes see (1975AJ02, 1985AJ01).
Inelastic scattering has also been reported to ^{12}C*(4.4, 9.6 ± 0.2, 11.8 ± 0.2, 12.7, 13.3 ± 0.2, 17.2 ± 0.2, 18.3 ± 0.2, 20.5 ± 0.2, 2224 (giant resonance), 26.5 ± 0.4, 29.5 ± 0.3): see details in (1980AJ01) and (1980IS09, 1980IS13, 1982NOZV). The E_{x} of ^{12}C*(4.4) is reported as 4439.4 ± 1.6 keV (1977WE1C), and the lifetime of the 4.4 MeV state was determined as τ_{m} = 65 ± 12 fsec (1958RA14). Resonance scattering and absorption by ^{12}C*(15.11) have been studied by many groups: see 12.15 (in PDF or PS) in (1968AJ02). The branching ratios and partial widths are displayed in 12.9 (in PDF or PS) in (1975AJ02) and 12.14 (in PDF or PS). The scattering angular distribution indicates dipole radiation (1959GA09), the azimuthal distribution of scattered polarized radiation indicates M1 (1960JA01) and the large Γ_{γ} indicates T = 1. The branching ratio for the cascade decay via ^{12}C*(4.4) was reported as (3.6 ± 0.7)% (1970AH02). The groundstate width of ^{12}C*(16.11) was first reported as Γ_{γ0} = 7.5 ± 1.9 eV (1959KE19): see, however, 12.14 (in PDF or PS) which shows a much smaller accepted value. For ^{12}C*(17.22), the scattering cross section is 1.0 ± 1.0 μb, consistent with Γ_{γ} from ^{11}B(p, γ) (1963SC21). At higher energies, elastic scattering studies show the giant resonance peak at ≈ 24 MeV. A considerable tail is visible, extending to > 40 MeV (1959PE32). At E_{γ} = 23.5 MeV, the peak of the giant resonance, the total photonuclear absorption cross section is 19.7 ± 0.4 mb (1983DO05), and Γ_{1}/Γ_{0} = 0.23 ± 0.07. In (1990SC02) the cross sections were measured for E_{γ} = 15 to 140 MeV using tagged Bremsstrahlung photons. At low energies, ^{12}C*(15.1) and the GDR are prominent, while the scattering cross section is essentially flat above E_{γ} = 30 MeV. The ^{12}C*(16.1) state and additional strength are observed in the inelastic scattering to ^{12}C*(4.4). The ratio of dσ(150°)/dσ(60°) was studied in this range to reveal E1/E2 interference effects; E2 states are suggested near E_{x} = 28 and 32 MeV. Previous measurements of the cross section at θ = 90° and 135° for E_{γ} = 23.5 to 39 MeV indicated a significant E2 strength [1.9^{+0.8}_{0.7} total isoscalar + isovector energy weighted sum rule] in addition to the dominant E1 strength (1980DO04, 1983DO05). However, measurements of the elastic differential cross sections for E_{γ} = 22.5 to 52.0 MeV (θ = 45°, 90°, 135°) reported by (1984WR01, 1985WR02) were inconsistent with the results of (1980DO04, 1983DO05). The difference between the measured energyintegrated values of σ(γ) and the E1 part of the photoabsorption cross section σ_{E1}(γ) was small and not sufficient to verify E2 strength (1985WR02). The scattering cross section has been measured for E_{γ} = 150 to 400 MeV by (1984HA08). Angular distributions for elastic and inelastic scattering are measured at E_{brem} = 158.8, 195.2, 197.2, 247.2 and 290.2 MeV (1995IG01). Measurements of elastic and inelastic scattering to ^{12}C*(4.4) at E_{γ} = 200 to 500 MeV, including the Δresonance region, are given in (1993AH01, 1994WI13). A measurement of the total photoabsorption cross section for E_{γ} = 600 to 1500 MeV is given in (2010RU16). See theoretical analyses in (1996PA06, 1998HU01, 2002SC15, 2002VA01). For pairproduction measurements at E_{brem} = 4.2 to 31.1 MeV see (1983NO06). The polarizabilities of bound nucleons in ^{12}C and ^{16}O were measured at E_{γ} = 61 and 77 MeV (1992LU01). The deduced values, α̃_{N} = (11.5 ± 0.8 (stat.) ± 2.1 (sys.)) × 10^{4} fm^{3} and β̃_{N} = (2.5 ∓ 0.8 (stat.) ± 2.1 (sys.)) × 10^{4} fm^{3}, are in close agreement with the values for free nucleons. However, see the analysis of (2001WA24: E_{γ} = 84 to 105 MeV), which suggests that definite conclusions are severely hampered by model dependencies. See also (1995HA23: E_{γ} = 58 and 75 MeV, 2014MY01: E_{γ} = 65 to 115 MeV).
Elastic scattering has been studied up to several GeV. The form factor is well accounted for by a harmonicwell model. Measurements of the elastic scattering form factor indicate the nuclear charge radius is < r^{2} >^{1/2} = 2.471 ± 0.009 fm [2.478 fm with dispersion corrections] (1991OF01), 2.464 ± 0.012 fm [2.468 fm with dispersion corrections] (1982RE12) and 2.472 ± 0.015 fm (1980CA07). This compares with < r^{2} >^{1/2} = 2.4829 ± 0.0019 fm from muonic Xray studies (1984RU12). Other values are reported in (1968AJ02, 1975AJ02). See also (1995AN02, 1995AN13, 2010HA14). (1991OF01) reports evidence for an energy dependence of the elastic form factors. The isoscalar vector hadronic coupling constant, γ = 0.136 ± 0.032 (stat.) ± 0.009 (sys.) (1990KO47, 1990SO03, 1991SO08), is determined from analysis of parity violating electroweak asymmetry in elastic scattering. Use of the parity violating elastic scattering asymmetries to obtain neutron densities is discussed in (2011MO35, 2012AB04, 2014MO03). See also (1990SU15, 1992MI09, 1993AL07, 1993AL20, 1993HO03, 1995KA14, 1998HO12, 2005ME10, 2009MO35). Sharp inelastic peaks are reported along with widths in 12.26 (in PDF or PS). See also (2009DE14, 2011AN17). A study of the (e, e'γ) reaction by (1985PA01) shows that the relative phase of the longitudinal and transverse form factors of ^{12}C*(4.4) is negative. Inelastic scattering data for the ^{12}C*(7.65) Hoyle state at E_{e} = 73 MeV was collected and analyzed along with the world data resulting in the value Γ_{π} = 62.3 ± 2.0 μeV for radiative decay (2009CHZX, 2010CH17, 2011VO16). This value is compared with prior measurements and other analyses; see (2005CR03) and (2014FR09) for references. Analysis of data in (2007CH04) suggests that the Hoyle state is dilute with a radius about 1.5 times larger than that of the ground state. The longitudinal form factor for the J^{π}; T = 1^{}; 0 isospin forbidden transition to ^{12}C*(10.84), which is sensitive to isospin mixing, was analyzed and indicates a transition strength B(E1) = 0.39 ± 0.20 × 10^{5} e^{2} ⋅ fm^{2} (1995CA14). The isospin mixing between ^{12}C*(12.71) and ^{12}C*(15.11) [both J^{π} = 1^{+}; T = 0 and 1, respectively] has been measured by (1974CE01): β = 0.19 ± 0.01 or 0.05 ± 0.01. The inelastic scattering to ^{12}C*(12.71, 15.11) was analyzed at q < 0.5 fm^{1}, Γ_{γ0} = 0.32 ± 0.02 eV and 35.0 ± 1.1 eV were deduced, respectively (2000VO04). The results were combined with (1972SP1C) and (1973CH16) (other low q results) and produced an average of 35.9 ± 0.06 eV for the later transition. These compare with 38.5 ± 0.8 eV from (1983DE53). The Coulomb matrix element was also analyzed in (2000VO04); ME = +118 ± 8 keV was deduced. The longitudinal form factors show ^{12}C*(16.1, 18.6, 20.0, 21.6, 22.0, 23.8, 25.5) while the transverse form factors show ^{12}C*(15.1, 16.1, 16.6, 18.1, 19.3, 19.6, 20.6, 22.7, (25.5)). At E_{e} = 150.6 MeV (θ = 180°) two peaks are observed at 16.1 and at 19.6 MeV corresponding to E2 and M2M4 excitations (1984RY01). There appears to be evidence for structures at 18.1 ± 0.05, 19.5 ± 0.05 (Γ = 0.5 ± 0.1), ≈ 24 and ≈ 34 MeV (1964GO14). The variation of F(q^{2}) with q^{2} in the range 00.6 fm^{2} shows good agreement with the calculations of (1964LE1D) which assumes four 1 particlehole states at E_{x} = 19.6, 23.3, 25.0 and 35.8 MeV (see also (1967CR02)). The behavior of the 19.2 MeV level suggests ascription to the expected giant magnetic quadrupole state J^{π} = 2^{}; this state is not likely to have been seen in ^{11}B(p, γ)^{12}C (1965DE1C, 1965DE1K, 1967BI1K, 1967CR02). A positive parity state with a large longitudinal matrix element may also be present (1967BI1K). No ΔT = 2 excitations were observed in a search for isotensor components of the electromagnetic interaction (1993LO13). Results and general analysis on scattering at medium to high energies are given in (1990DA14, 1991BR13, 1991BU04, 1991DE32, 1991ER06, 1991TA23, 1992PR01, 1992WA19, 1993AM11, 1993AR06, 1993DE33, 1994AM06, 1994JE04, 1995AV01, 1995DO23, 1995JO21, 1995MO11, 1995VA12, 1995VA33, 1997GI12, 1998RI01, 1999GU20, 2001CA04, 2001GU16, 2002CA26, 2003KI06, 2003KI09, 2003ME09, 2004KI21, 2005KI26, 2006KU01, 2006MA62, 2008CE01, 2009LI04, 2010AM01, 2010HA14, 2014KI06, 2015LO05, 2015MO24, 2015PA35, 2016RO32). Reviews on the scaling and superscaling behavior of quasielastic electron scattering reaction cross sections are found in (2009MA57, 2010CA14). See other detailed discussion on scaling approaches in (1999DO05, 2003HA44, 2005AM03, 2005NA03, 2006BA62, 2006CA22, 2006CO15, 2007AM01, 2007KI16, 2007MA18, 2009AN06, 2009CI01, 2009MA57, 2009ME07, 2010AM01, 2011AN09, 2015AM02, 2015BE26, 2015KI01, 2016IV03). Electroproduction of hypernuclei is discussed in (1998HI15, 2003MI11, 2003TA41, 2005GA09, 2006YU03, 2007IO02, 2007TA25, 2008HA14, 2008LE08, 2010FU13, 2010GA29, 2014TA26).
In (1984CA34) evidence for a monopole, J^{π} = 0^{+}, state near E_{x} ≈ 20.5 MeV which exhausts at least 1% of the energy weighted sum rule is found in (e, e'p_{0}). The decay of states in the giant resonance region via αparticles has been studied by (1993DE10, 1995DE23): the E2 decay is primarily to ^{8}Be*(2.9[J^{π} = 2^{+}]) and reveals a peak with E_{x} = 21.6 and Γ ≈ 1.5 MeV; see also (1991PO06, 1994CA08, 1999SA27). Electron spectra in the region of large energy loss show a broad peak which is attributed to quasielastic processes involving ejection of single nucleons from bound shells; studies of e'p coincidences reveal peaks corresponding to ejection of 1p and 1s protons (at 700 MeV the energies of the peaks are 15.5 ± 0.1 and 36.9 ± 0.3 MeV with Γ = 6.9 ± 0.1 and 19.8 ± 0.5 MeV, respectively [1976NA17: DWIA]). Spectroscopic factors for 1s [ = 1.50 ± 0.08 (2000LA23)] and 1p [= 3.56 ± 0.12 (2000LA23)] shell singleparticle knockout reactions are discussed in (1990CA14, 1990DE16, 1990WE06, 1991WE10, 1991WE16, 1994IR01, 1994IR02, 1995BL10, 1995KE03, 1998WO01, 1999DO30, 1999RY06, 2000DU12, 2000LA23, 2002MA12). At 500 MeV the quasielastic scattering cross section has been analyzed and indicates the Fermi momentum is 221 ± 5 MeV/c (1971MO06). Studies of the quasielastic longitudinal and transverse response functions versus missing energy have been carried out. (1987UL03) find in the longitudinal response a broad bump at missing energies between 28 and 48 MeV, attributed to knockout from the sshell. In the transverse response they find this bump on top of a broader feature with a threshold at 28 MeV extending beyond 65 MeV. This broad feature is attributed to twoparticle knockout, a nonquasielastic reaction mechanism; it may account for the observed (e, e') transverselongitudinal difference. This feature is also observed in unseparated data at larger momentum transfers: it appears to grow with momentum transfer (1988WE1E). See also (1992BO10, 1992WA19, 1994MA26, 1995JO21, 2003AN15, 2003DE10, 2005MO04). Multinucleon correlations and fewbody interactions are discussed in (1993KE02, 1995KE03, 1995KE06, 1996KE03, 1996RY04, 1997RY01, 1998AL03, 1998BL06, 1998RY05, 2000DE58, 2000RO17, 2004MU29, 2005HO18, 2005KE06, 2006EG02, 2007PI05, 2009CI01, 2014CO05). Nucleon excitation studies are discussed in (1993RO13, 1995NI01, 1995ZO01, 1997GI02, 1997GI12, 1998GA25, 1999BA31, 2004BO47, 2008BO24, 2011VA11). Effects such as transparency of the nuclear medium have been studied by (1990FR11, 1992BE23, 1992FR17, 1992GA02, 1992JE03, 1992PA03, 1993LO01, 1993NI11, 1994FR12, 1994FR16, 1994GR05, 1994IR02, 1994KO21, 1994MA23, 1994NI05, 1995FR04, 1996KE14, 1996NI13, 1997AL20, 1997IW03, 1999RY06, 2000DU12, 2000LA23, 2001FR06, 2002DE11, 2002GA43, 2002ME11, 2002ME17, 2003DU23, 2003RY02, 2004BA99, 2004BO47, 2004HA63, 2004LA13, 2005RO38, 2006RO37, 2007CL04, 2009KA02, 2010QI02, 2013RO06). Discussion on other final state effects is given in (1991CA09, 1994IR02, 1994JE04, 1994RY04, 1995BI07, 1995BI19, 1995NI02, 1996BI01, 1996BI21, 1996JE04, 1999KE04, 2002DE07, 2004BA99, 2004BB15, 2005BA07, 2005BA23, 2005PR02, 2007AL14, 2007PI05), and discussion on the reaction mechanism is found in (1990LO09, 1991VA05, 1992DR02, 1993CI05, 1993OF01, 1994IR01, 1994RY03, 1994TA11, 1994WE06, 1999MO02, 2002ME17, 2004FR27, 2004MU29, 2004RO35, 2004TA18, 2011RY03). See also (1993KE02, 1993KO12, 1994BI05, 1994VE08, 1994WA19, 1995RY02, 1996JO15, 1997BI06, 1997GI13, 1998HO20, 1999JO06, 2000DE38, 2000UD01, 2005KE04, 2009TA34, 2014MO25, 2014TO14).
Parity violating muon scattering is discussed in (1993MI03). A review of μ^{}e^{} conversion reactions is given in (2006DE31). Cosmogenic production of nuclides, such as ^{11}C, is discussed in (2005GA19, 2006BA66, 2000HA33).
Angular distributions of the elastic and inelastically scattered pions have been measured at many energies: see 12.27 (in PDF or PS). See theoretical analysis in (1990BE53, 1990ER06, 1990FR02, 1990LI10, 1990MI08, 1990TA13, 1991AL01, 1991AR12, 1991OS01, 1991TA01, 1992BI06, 1993CH04, 1993CH16, 1993CH25, 1993MO27, 1993NI02, 1993PE09, 1994CH30, 1995AR02, 1995BA92, 1995KA49, 1996BI12, 1996CH16, 1996EB02, 1997SC09, 1998AH06, 1998CH42, 1998NU02, 1998PE09, 1998RO15, 1999HO13, 1999TA33, 2000EB05, 2000KH17, 2002NO13, 2004SA28, 2005EB03, 2005HA26, 2006AH02, 2006KA47, 2009FA02, 2010IO02, 2011EB03, 2013EB02, 2013KH17). Angular correlations for π'γ_{4.4} and π'γ_{15.1} reactions have been studied by (1984SO12, 1984VO04, 1986OL07, 1988OL02) and (1988BA27), respectively. A detailed analysis of the sum rules for population of the J^{π} = 1^{}; T = 0 ^{12}C*(10.84) state is given in (1993KO17). The possible group to ^{12}C*(15.4) has a width of ≈ 2 MeV (1981MO07); ^{12}C*(14.1, 16.1) were also populated. J^{π} = 2^{} for ^{12}C*(18.25, 19.4) and J = 4 for ^{12}C*(19.25) are suggested in (1987CO17); ^{12}C*(19.65) is also populated. Study of the giant resonance region suggests states at E_{x} = 19.85, 22.10, 22.94, 23.70 and 25.40 MeV with Γ ≈ 330, 198, 192, 79 and 232 keV, respectively (1993KO17). See also E_{x} = 20.0 ± 0.2 and 22.7 ± 0.4 MeV, with Γ = 3.2 ± 0.3 and 1.0 ± 0.2 MeV (1984BL12) and E_{x} ≈ 18.3, 19.3, 22.1, 23.7 and 25.6 MeV (1982MO25). A strong energydependent enhancement in the pion scattering to ^{12}C*(15.1) but not to ^{12}C*(12.7) is observed at E_{π±} = 100, 180 and 230 MeV: this is interpreted as possible evidence for direct (Δh) components in the wave function of the T = 1 state (1982MO01). The chargedependent matrix element between the J^{π} = 1^{+}; T = 0 and 1^{+}; T = 1 states, ^{12}C*(12.71, 15.11), was studied by (1990JA05); ME = 157 ± 35 keV was deduced. See the results of (1981MO07) along with other values in 12.18 (in PDF or PS). The ratio of the cross sections to, ^{12}C*(12.7, 15.1) at E_{π±} = 50 MeV is 7.1 ± 1 [isospin averaged] (1988RI03). The excitation of these two states has also been studied for E_{π±} = 80 to 295 MeV by (1988OA03). A preliminary value for the isospin mixing matrix element between ^{12}C*(18.4, 19.4), 250 ± 50 keV, was given in (1979BO2D, 1979MO1W: E_{π} = 116, 180 MeV). The emission of 2 photons in the capture of stopped pions, i.e. (π^{}, γγ), occurs at a rate of (1.3 ± 0.3) × 10^{5}/capture (1979DE06). Strong energy dependence is observed in the π^{+} absorption (1981AS07, 1983NA18). At E_{π±} = 50 MeV the absorption of π^{} is about twice that of π^{+} (1983NA18). Analysis of 4.4 MeV γrays produced at E_{π} = 73 MeV yields σ(π^{+}) = 14.5 ± 3.0 mb and a cross section ratio, σ(π^{})/σ(π^{+}), of 1.23 ± 0.22 (1970HI10). The Fermimomentum distribution of protons was measured using reaction (b) at E_{π} = 0.7, 0.9 and 1.25 GeV (2000AB25).
Angular distributions and differential cross sections of elastically and inelastically scattered neutrons have been measured at many energies up to 350 MeV [see 12.28 (in PDF or PS)]. See other results in (1995TI10, 1995ZH49, 2013NE11). Discussion on polarization measurements is given in (1995CH12, 1995CH44, 2005CH58, 2006SV01, 2010WE06). For Optical Potential analyses see (1990NI02, 1991SH08, 1997EL13, 2001KA58, 2009WE04, 2011JA09, 2011RA34, 2012JA03, 2012PA09, 2015GH04, 2016AL14, 2016XU07); for Coupled Channels analyses see (2003AM08, 2005CA16, 2006SV01); for other analyses see (1990BE54, 1991BA39, 1992GA26, 1992KA14, 1992KA21, 1994IS08, 1994XI04, 1996CH33, 1996CH49, 1996GO48, 1997HA21, 1998SU23, 1999SU01, 2000CH31, 2000KE13, 2005PI16, 2008FR02, 2008FR11, 2008GE04, 2009AL05, 2009AL10, 2010NA18, 2016AR13, 2016FR09). Angular correlations of (n, n'γ_{4.4}) have been studied at E_{n} = 13.9 MeV (1973DE45) and 15.0 MeV (1971SP01), and at 14 to 14.7 MeV [see (1968AJ02)]. The spinflip probability for the transition to ^{12}C*(4.4) has been studied at E_{n} = 7.48 MeV (1971MC1K, 1972MC20) and at 15.0 and 16.9 MeV (1973TH08, 1974ME29). Its shape at E_{n} = 7.48 MeV is similar to that measured by (1964SC07) in the (p, p') reaction at E_{p} = 10 MeV (1972MC20); while that at E_{n} = 16.9 MeV the shape is similar to that measured by (1969KO07) at E_{p} = 20 MeV (1974ME29). The quadrupole deformation parameter β_{2} = 0.67 ± 0.04 (1983WO02). For reaction (b), complete kinematics involving ^{12}C*(7.65, 9.64, 10.84, 11.8, 12.7, 14.0, 15.1, 16.1) were studied at energies between E_{n} = 11.5 to 19 MeV (1991AN06). At E_{n} = 14.4 MeV ^{12}C*(9.6, 10.8, 11.8, 12.7) have been reported: see (1975AJ02). A detailed study on the population of ^{12}C*(9.6) at E_{n} = 11 to 35 MeV is given in (1983AN02): the decay is dominated by sequential feeding of ^{8}Be_{g.s.} at the higher energies; see also (1953JA1C). The αdecay of the 10.8 and 11.8 MeV states, together with stripping results, suggest J^{π} = 1^{} and 2^{} for these states (1964BR25, 1971DO1K, 1975AN01, 1975AN02; see also (1966MO05)).
Angular distributions of elastically and inelastically scattered protons have been measured at many energies up to E_{p} = 1040 MeV: see 12.29 (in PDF or PS). 12.30 (in PDF or PS) displays the information on excited states of ^{12}C. A summary of the decay of some excited states is shown in 12.14 (in PDF or PS). The angular distributions have been analyzed by DWBA (and CCBA), DWIA (including microscopic calculations) and DWTA (DW tmatrix approximation with densitydependent interactions). Microscopic DWIA calculations give good results for transitions which proceed through the S = T = 1 part of the effective interaction and also give a reasonable description of the S = T = 0 transition. However the mechanism for the excitation of ^{12}C*(12.71) (S = 1, T = 0) remains a puzzle (1980CO05: E_{p} = 122 MeV). The angular distributions of the inelastically scattered protons to ^{12}C*(12.71) are usually poorly fitted: see e.g. (1990IE01). In (1995SA28) the 0° cross sections were measured for ^{12}C*(12.71, 15.11) at E_{p} = 65 to 400 MeV; the cross sections, which maintained a nearly consistent ratio at all energies, were evaluated via microscopic DWIA analysis that reproduced the data best by reducing the isovector tensor terms of the effective interactions. Also see the analysis of spin observables at E_{p} = 198 MeV, for ^{12}C*(12.71, 15.11) up to q ≈ 200 MeV/c (2001OP01). At E_{p} = 402 MeV the differential cross sections for ^{12}C*(12.7, 15.1) (J^{π} = 1^{+}) are very similar for large q. This may be due to the smallness of precursor effects [precursor to a pion condensate] (1981ES04). The spinflip probability (SFP) for the transition to ^{12}C*(4.4) has been measured for E_{p} = 15.9 to 41.1 MeV: two bumps appear at E_{x} ≈ 20 and ≈ 29 MeV. It is suggested that the lower one is due to a substructure of the E1 giant dipole resonance while the upper one results from the E2 giant quadrupole resonance (1975DE32, 1982DE02). The SFP has also been studied at E_{pol. p} = 24.1, 26.2, 28.7 MeV (1981FU12: to ^{12}C*(4.4)), at E_{p} = 42 MeV (1981CO08: to ^{12}C*(12.7)), at E_{pol. p} = 397 MeV (1982SE12: to ^{12}C*(9.6, 12.7, 15.1, 16.1)) [the SFP to ^{12}C*(9.6) is consistent with zero; the others exhibit large SFP at forward angles] and at E_{p} = 398, 597 and 698 MeV (1983JO08: to ^{12}C*(18.3, 19.4)). The SFP has also been measured for ^{12}C*(12.71) at E_{p} = 42 MeV (1977MO18) and for ^{12}C*(12.7, 15.1) at E_{p} = 23.5 to 27 MeV (1978HOZJ) and E_{p} = 500 MeV (1991CH31). The SFP was measured in the region of 5 < E_{x} < 30 MeV (1999TA22) and 10 < E_{x} < 40 MeV (1993BA37); see also (1990BA14, 1990BA61). (1980HO07) have measured the angular distribution of γrays from the decay of ^{12}C*(12.7, 15.1) at E_{p} = 21.5 to 27 MeV. Microscopic DW calculations were performed for the A_{0} and a_{2} coefficients from these and earlier data. The theoretical calculations underestimate A_{0} for energies below 35 MeV and are in agreement with the experimental A_{0} for higher energies. The calculations also predict significant differences in the a_{2} values for the transitions from ^{12}C*(12.7, 15.1), and these are observed (1980HO07). Angular distributions show that a large deformation exists: β_{2} = 0.72 (1972DE13) and 0.6 (1967SA13); β_{2} = 0.663 and β_{4} ≈ 0 (1983DE36); β_{2} = 55 ± 11, β_{0} = 0.15 ± 3 and β_{3} = 0.39 ± 8 (2010OK01). A DWBA analysis in (2010OK01) suggests ^{12}C*(7.65) has a structure that is consistent with the assumption of a dilute αcluster condensed state as suggested by (2001TO23). The pγ_{4.4} angular distributions have been studied at E_{p} = 7.5 MeV (2006LE45). The pγ_{15.1} angular correlations have been studied at E_{pol. p} = 100 to 180 (1990PI06) and E_{p} = 200 MeV (1995WE10), 318 MeV (1992LY01) and 400 MeV by (1988HI12). See also (1990PI06, 1995SU30). A study at E_{p} = 66 MeV measured Γ(9.64) = 48 ± 2 keV (2013KO14). Evidence for the J^{π} = 2^{+} excitation of the E_{x} = 7.65 MeV "Hoyle state" has been reported in (2009FR07, 2010FR03, 2012FR05: E_{x} = 9.75 ± 0.15 MeV with Γ = 0.75 ± 0.15 MeV) and (2011ZI01: E_{x} ≈ 9.6 MeV). In these different experiments, the known states at (7.65, 9.6, 9.64, 10.83, 11.80, 12.71) were also observed. The Γ ≈ 600 keV width initially reported in the (p, p') work of (2009FR07) was reanalyzed in (2012FR05) along with the (α, α') data of (2011IT08) yielding the slightly higher Γ = 0.75 ± 0.15 MeV value. In (2009FRZV), the authors question the validity of the E_{x} = 11.16 MeV state reported previously in ^{11}B(^{3}He, d) reactions and they reiterate the likely ^{12}C*(13.35) J^{π} = 4^{} spin assignment previously suggested in (2007FR17). In (1997TE14), inclusive (p, p') and exclusive (p, p'p) and (p, p'α) reactions populated levels between 0 < E_{x} < 24.4 MeV. The GT_{+} strength distribution in ^{12}B was analyzed in (2001WO07) by comparing the ^{12}C*(15.1, 16.1, 18.35, 19.4, 21.6) excitations with the corresponding J^{π} = 1^{+}, 2^{+}, 2^{}, 2^{} and 2^{} excitations from ^{12}C(d, ^{2}He)^{12}B. For theoretical analysis of elastic and inelastic scattering see (1990TA13, 1990TA16, 1991LI07, 1991TA01, 1992WA19, 1993BY02, 1993DE33, 1995MA23, 1996BE25, 1997DO02, 1997TE14, 1998GI01, 1998GU13, 1998KI17, 1998SU23, 1999GU17, 1999NA43, 2000CH31, 2000DE37, 2000LO20, 2004YA24, 2005PI16, 2006GU23, 2008FR02, 2013WE05, 2015TO11). Analyses of spin observables and polarized beam results are found in (1990BA14, 1990HA45, 1990ST32, 1990TA17, 1991BE45, 1992BE03, 1992BE24, 1992SH01, 1993CH14, 1993CO02, 1993KA45, 1993LA27, 1994DO03, 1994HI02, 1994PH02, 1994WI09, 1995BU37, 1995CH12, 1995CH44, 1995DE32, 1995DO31, 1995KA24, 1996DE31, 1996KA65, 1997BB17, 1997DO01, 1998DO16, 1998HI02, 1999AN32, 2000WE01, 2001HI10, 2001RA06, 2004CU02, 2005DE32, 2006ON03, 2007KH12, 2007YA13, 2008FU13, 2008KI13, 2009CO17, 2010NA18, 2011FU16, 2013PL02, 2014PL05). Global studies evaluating protons on a variety of targets are given in (1990BA14, 1990BA61, 1990HU09, 1990KA05, 1990PH02, 1990ST32, 1992KO04, 1993BE10, 1993CH14, 1993CO02, 1993KA45, 1994HA48, 1994WI09, 1995CH12, 1995CH44, 1995ER10, 1996GO48, 1997DO01, 1998DO16, 1999KU07, 2000DE43, 2000KE13, 2001KA58, 2002DI04, 2002FA14, 2002SA49, 2002TR12, 2005DE32, 2005KI04, 2005KO28, 2007KH12, 2007TA27, 2008FU13, 2008HA03, 2008KI13, 2009CO17, 2009WE04, 2010NA18, 2012DY01, 2012PA09, 2013ZU04, 2014HL01, 2015AR01, 2015BE12, 2016AR13). See also (1997IL02, 1998BA59, 1998KI15, 2001KI25, 2001WO07, 2010AZ01, 2011DU06: astrophysics).
The (p, 2p) reaction has been studied up to energies above 1 GeV. At E_{p} = 56.5 MeV, p_{0}decay from a state at ^{12}C*(20.3 ± 0.5) was reported (1969EP01). 12.31 (in PDF or PS) shows states populated in reactions with 156 MeV protons. The analysis suggests the region above E_{x} = 21 MeV is dominated by J^{π} = 1^{}; T = 1 resonances that mainly deexcite via singlenucleon emission. States in ^{11}B are studied in (2004YA20, 2004YO06). At higher energies, quasifree knockout reactions from distinct shells are observed; see experimental results reported in (1997HA15, 1998MA67, 1998NO04, 1999AC03, 1999CA11, 1999CA15, 2000NO03, 2003TA03, 2004AC08, 2004AN01, 2007RY02, 2008NO01). Discussions include pp correlations, initial and final state effects, such as color transparency and nuclear modifications to the NN interaction; see (1992LE03, 1994FR12, 1994FR16, 1994KO21, 1995GA46, 1997GA16, 2000ST17, 2006DA15, 2006HI15, 2006VA08, 2007DA19, 2009CO10, 2011RY03, 2014CR05, 2015MO21, 2015OG03). Although the shapes of the momentum distributions in the (p, pn) reaction (reaction (b)) at 400 MeV are consistent with quasifree knockout, the magnitude of the cross section relative to that for the (p, 2p) process is inconsistent with the PWIA model (1979JA20). However, a study of inclusive (p, p') reactions along with exclusive (p, p'n) and (p, 2p) reactions at E_{p} = 200 MeV (1999CA11, 1999CA15) found that a comprehensive accounting of pshell knockout and sshell knockout to excited states in the residuals was consistent with DWIA calculations, and apparently validated the impulse approach at this energy regime and lower. See also (2015MO21: theory) and ^{11}C yield measurements in (1993KO48). The ^{12}C(p, pd) missing energy spectrum at E_{p} = 670 MeV (reaction (c)) shows a strong bump at E_{miss} = 25 MeV and a weaker one at E_{miss} = 45 MeV, corresponding to the ^{10}B groundstate and ^{10}B*(20) regions, respectively (1981ER10). See also (1990LO18). For reaction (d), at E_{p} = 56.5 MeV (1969EP01) T = 0 states at ^{12}C*(22.2 ± 0.5, 26.3 ± 0.5) were reported to α_{0}decay (natural parity) while states at ^{12}C*(19.7, 21.1, 26.3) were found to α_{1}decay. It is suggested that ^{12}C*(21.1) has unnatural parity. At E_{p} = 44.2 MeV ^{12}C*(12.7, 14.1, 21.6, 26.6) are observed in the angular correlations involving α_{0}; states at ^{12}C*(21.6, 24.1, 26.6) decay via α_{1} to ^{8}Be*(3.0) [suggesting 2^{+} for these states, assuming that only resolved states are involved (1981DE08)]. A detailed analysis of the ^{12}C(p, p3α) reaction at E_{p} = 14, 18 and 26 MeV (1999HA27) indicates the involvement of ^{12}C(p, p'α)^{8}Be and ^{12}C(p, α)^{9}B reaction channels. Other measurements at E_{p} = 101 MeV (2009CO01, 2009MA21) and E_{p} = 296 MeV (1998YO09) probed the cluster nature of ^{12}C by evaluating alpha cluster spectroscopic factors and quasifree scattering; consistency with free scattering was found. See also (1994NE05, 1995GA39, 1995NE11, 1995TC01, 1997NE05, 1997SA04).
The angular distribution of elastically and inelastically scattered deuterons has been studied at many energies: see 12.32 (in PDF or PS). Measurements aimed at refining global model parameters are found in (1993BE43, 2001BA18); see also (1990GO28, 1990HU09, 1990ST32, 1992RA31, 2003EL08, 2004KE08, 2006AN14, 2006HA42, 2006PR13, 2008CHZT, 2010GU03, 2011MI20, 2012PA22, 2012UP01, 2016ZH26). Fewbody and cluster model analyses are given in (1997MI29, 1999BR09, 2000MI36, 2007AL28, 2008FO06, 2009DE08, 2013BE27, 2014BE17). In (2009DA22, 2010OG03) a method is suggested for determining nuclear radii of unstable states by analysis of diffractive scattering; rootmeansquare radii are estimated for ^{12}C*(7.65. 9.64, 9.9, 10.3, 10.84). In addition to wellknown states in ^{12}C such as ^{12}C*(4.4) [E_{x} = 4440.5 ± 1.1 keV (1974JO14)] and ^{12}C*(12.7, 15.1) [see 12.18 (in PDF or PS) for chargedependent matrix element results], the population of ^{12}C*((10.8 ± 0.2), (11.8 ± 0.2), 18.3 ± 0.3, 20.6 ± 0.3, 21.9 ± 0.3 (broad), ≈ 27 (broad)) is also reported (1975AS06). The J^{π} = 2^{} state here at 18.3 MeV is different from the 18.4 ± 0.2 MeV J^{π} = 2^{+} state observed in α inelastic scattering (1995JO06). DWIA analysis indicates J^{π} = (1^{+}) for E_{x} = 20.4 MeV and L = (1) for E_{x} ≈ 30 MeV (1994MO21). The GDR region was studied in (2008GR22). A preliminary report (1977CH1L) suggested two structures at E_{x} = 26 ± 1 and 29 ± 1 MeV, with Γ = 2 ± 1 and 4 ± 1 MeV, respectively, and determine L = 3 in the excitation of ^{12}C*(18.4). Isoscalar spin strengths and spinflip probabilities are reported at E_{pol. d} = 53 MeV (1993IS04), E_{pol. d} = 270 MeV (2001SA68) and E_{pol. d} = 400 MeV (1995JO06); S_{1} shows peaks for E_{x} = 12.71 and 18.35 MeV and suggestions of peaks above 20 MeV while S_{2} is consistent with zero up to E_{x} = 24 MeV range (2001SA68). Polarization observables are reported at, for example, E_{d} = 200 MeV (2004KA53), E_{d} = 393 MeV (1995FU03: E_{x} = 12.7 MeV) and E_{d} = 1.8 GeV (1995TO15). See also theoretical analysis in (1990SA45, 2001HI10, 2009DE02, 2009DE13). The quadrupole deformation parameter is calculated to be β_{2} = 0.48 ± 0.02 independent of incident energy [E_{d} = 60.6, 77.3, 90.0 MeV] (1975AS06: coupled channels analysis). (1971DU09: E_{d} = 80 MeV) report β_{2} = 0.47 ± 0.05 and β_{3} = 0.35 ± 0.06 for ^{12}C*(4.4, 9.6), respectively. See also β_{2} = 0.5 (2007GA07). Reaction (b) was measured at E_{d} = 56, 140 and 270 MeV (1994OK01, 1998OK04); the results indicate sensitivity to Coulombdissociation and dissociationdiffraction mechanisms (1990SA45, 1991EV03, 1995SA39, 1996SA10, 1998NA42, 1998TO08, 1998TO10, 2002ZA10, 2006EV05, 2012UP01). See also (2002EV01, 2003EV01, 2009DE08, 2014YE03, 2016OG02). Earlier results are reported at E_{d} = 5.00 to 5.50, 9.20 and 9.85 MeV (1973SA03), 5.1 to 6.25 MeV (1973SH04), 5.4 and 6.0 MeV (1968BO02), 5.5 to 6.5 MeV (1972VA10), 56 MeV (1983BA37) and 2.1 GeV (1989PU01). For reaction (c) see ^{8}Be in (1979HE06).
Angular distributions of elastically scattered tritons have been measured at E_{t} = 1 to 20 MeV. See (1968AJ02: E_{t} = 1 to 12 MeV), (1975AJ02: E_{t} = 1.11 to 20 MeV), (1980AJ01: E_{t} = 9.0 to 17 MeV) and (1990AJ01: E_{t} = 33, 36 MeV). See also the optical model analyses for E_{t} < 40 MeV in (2007LI55, 2009PA07, 2015PA10).
Angular distributions of ^{3}He ions have been measured for E(^{3}He) = 2 to 217 MeV: see 12.33 (in PDF or PS). Parameters of observed ^{3}He groups are displayed in 12.34 (in PDF or PS). See analysis on angular distributions in (1995GA22, 1997KH07, 2000MO34, 2001KU20, 2003BE70, 2003KH01, 2004BE42, 2007LU04, 2007OH01, 2008DE35, 2009GU16, 2009PA07, 2010HA19, 2015PA10). In (2003KH01), E(^{3}He) = 72 MeV data are analyzed and the deformation length δ_{2} = 1.05 fm is deduced for ^{12}C*(4.44). The ^{3}Heγ_{4.44} angular correlations were measured in (1994IG01). See (2003KA24: E = 443 MeV) for polarization observables. Rainbow effects and Airy patterns are discussed in (1990DE31, 1990KU25, 1991GO25, 1991KU29, 1992AD06, 1992DE18, 1995DA08, 1995DA21, 1995GA22, 2010OG03). The radius of the ^{12}C*(7.65) Hoyle state is reported as 2.94 fm or 1.21.3 times larger than the g.s. radius (2008DE35); see additional comments on the dilute nature of the Hoyle state structure in (2006OG04, 2007OH01, 2008DE35, 2009DA22, 2010OG03, 2013HA01). Angular distributions of the ^{3}He groups to ^{12}C*(15.11, 16.11, 16.58, 19.56) have been compared with those for the tritons to ^{12}N*(0, 0.96, 1.19, 4.25) in the analog (^{3}He, t) reaction: the correspondence is excellent and suggests strongly that these are T = 1 isobaric analog states (1969BA06: E(^{3}He) = 49.8 MeV). See also 12.12 (in PDF or PS) in (1980AJ01) and 12.34 (in PDF or PS). At E(^{3}He) = 46 MeV, the inelastically scattered ^{3}He projectiles were detected along with the 3α particles from the breakup of αunbound states (2014WH02); levels up to E_{x} = 25.1 MeV are observed. The states reported by (1977BU03) at E(^{3}He) = 130 MeV [see 12.34 (in PDF or PS)]: ^{12}C*(4.4, 15.2, 18.4, 18.9, 21.3, 23.5, 25.9, 28.8) are all suggested to correspond to E2 transitions: their strengths add up to 46% of the EWSR (energyweighted sum rule). The quadrupole deformation parameter β_{2} = 0.30 can account for both the elastic and inelastic data providing that the ratio of the spin orbit and central deformation β_{s.o.}/β_{cent.} is energy dependent (E(^{3}He) = 20.5 to 33 MeV) (1977KA25). In (1980LE25) states were reported at E_{x} = 9.15 ± 0.2 and 20.3 ± 0.2 MeV [Γ = 1.8 ± 0.2 and 1.1 ± 0.2 MeV, respectively]: it was suggested that both are E0 states whose intensities are (2.1 ± 0.4)% and (2.6 ± 0.2)% of the EWSR: however these states are not confirmed, see (1981EY02, 1981YO04) in reaction 46 of (1985AJ01). Cross sections are discussed in (1998BO39, 2008KO29, 2009LI01, 2011CH11). For discussion on Δresonance excitation and coherent π^{+} production see (1990UD01, 1991DE31, 1992HE08, 1993DM01, 1993FE10, 1993HE03, 1993OL06, 1993RO09, 1993RO30, 1994DM03, 1994JA12, 1994KO23, 1994OS02, 1994OS03, 1994SN01, 1994UD01, 1995KE13, 1995ST29, 1996GA20, 1996OS02, 1997KA52, 1998DA25, 2000BO47, 2002DA20, 2005AL37, 2005BO22).
Angular distributions have been measured at many energies up to 1.37 GeV: see 12.35 (in PDF or PS). Parameters of observed states of ^{12}C are displayed in 12.34 (in PDF or PS). See general theoretical analyses of the angular distributions in (1990AB10, 1990AL05, 1990BO23, 1990CO29, 1990HU09, 1990LE18, 1991AN21, 1991BA23, 1991KU30, 1991LI25, 1991OK02, 1991ZH27, 1992ZH06, 1992ZH40, 1993AL10, 1993TA30, 1994AH05, 1994IN01, 1994RU12, 1994RU15, 1995AI03, 1995KH07, 1996ZH36, 1997CH48, 1998EL14, 1998GA46, 1999GA43, 1999IG02, 2000AB16, 2000EB02, 2000EL03, 2000GU07, 2001EL05, 2001KH02, 2001KI25, 2002HI07, 2002KH01, 2003MO11, 2003ZE06, 2004YA03, 2005AL18, 2005GR40, 2005KU23, 2006FA09, 2006FU11, 2006KU16, 2008KH14, 2008ZO03, 2010IZ01, 2010KA21, 2011AL23, 2011BE20, 2011BE42, 2011GU15, 2012DY01, 2012GI01, 2012PA22, 2013LA28, 2015SU14, 2016AN08, 2016HU08, 2016MI13, 2017BE01). Structures in large angle scattering are discussed in (1990DA23, 1991GO25, 1994DA32, 1995DA08, 2004OH13, 2008DE35, 2011BE42) and studies of backward angles scattering are emphasized in (1990TO09, 1994DA16, 1994YO06, 1995EN09, 1996SO20, 1998BE56, 2002AN26, 2002AR16, 2004JI10, 2012MA26). The large radii deduced for ^{12}C*(7.65), R_{rms} = 2.89 ± 0.04 fm and ^{12}C*(9.9: J^{π} = 2^{+}), R_{rms}(2^{+}_{2}) = 3.07 ± 0.13 fm, are significantly larger than for ^{12}C*(4.44) and have been suggested as evidence for BoseEinstein condensate structures (2008DE35, 2009DA22, 2010OG03, 2011OG10, 2013OG05); see also (2004IT09, 2006OG04, 2006TA27, 2008KH02, 2008OHZX, 2008TA21, 2010BE32, 2010OG03, 2011IT08, 2016NA22). In (2004IT09), an L = 2 component of the reaction was identified near E_{x} = 9.9 MeV with Γ ≈ 1.0 MeV; the strength is associated with a rotational excitation of the Hoyle state. In (2011IT08), the state is identified at E_{x} = 9.84 ± 0.06 MeV with Γ = 1.01 ± 0.15 MeV. In (2012FR05) the (p, p') data from (2009FR07) and the (α, α') data from (2011IT08) are simultaneously analyzed via Rmatrix analysis, and the J^{π} = 2^{+}_{2} state is identified at E_{x} = 9.75 ± 0.15 MeV with Γ = 0.75 ± 0.15 MeV. The large α width associated with this J^{π} = 2^{+}_{2} state suggests a highly clustered structure. In addition to the discovery of the J^{π} = 2^{+}_{2} state, evidence is observed for other previously unreported states in the E_{x} = 912 MeV region. A group at E_{x} = 9.93 ± 0.03 MeV with Γ = 2.71 ± 0.08 MeV is identified with J^{π} = 0^{+} strength; it is suggested as a J^{π} = 0^{+}_{3} + 0^{+}_{4} doublet (2011IT08); this state is seen at E_{x} = 9.8^{+0.2}_{0.4} MeV with Γ = 2.7 ± 0.3 MeV in (2003JO07). Analysis in (2011IT08) suggests E_{x} = 9.04 ± 0.09 MeV and Γ = 1.45 ± 0.18 MeV for 0^{+}_{3} and E_{x} = 10.56 ± 0.06 MeV and Γ = 1.42 ± 0.08 MeV for 0^{+}_{4} states. Additional support for the interpretation of doublet J^{π} = 0^{+} states is found in the GCM calculations of (2016ZH43) and in the cluster model analyses of (2016FU07, 2016IS15). See also (2015FU09, 2016KA19, 2016YO09). At E_{α} = 240 MeV (2003JO07), some evidence for J^{π} = 2^{+} strength at E_{x} is reported at E_{x} =11.46 ± 0.20, but no evidence was seen for this state in the E_{α} = 386 MeV data of (2011IT08). In addition, the results of (2011IT08) don't find support for the J^{π} = 0^{+} and 2^{+} strength at E_{x} = 11.2 and 11.1 MeV, respectively, deduced in the analysis of the ^{12}B/^{12}N β decay data (2010HY01); however, differences in analysis approaches may explain the different findings. At present it is difficult to suggest a clear picture of the J^{π} = 0^{+} and 2^{+} strength has emerged. See a review of Eλ transition strengths for E_{x} ≤ 10.84 MeV in (2013CU05). Evidence for a Γ = 1.7 ± 0.2 MeV broad J^{π} = (4^{+}) state at E_{x} = 13.3 ± 0.2 MeV is seen in the reconstructed kinematics of 3α ejectiles (2011FR02). It is suggested that this state, along with the J^{π} = 0^{+}_{2} and 2^{+}_{2} states form a rotational band. Alphaalpha correlations from ^{12}C*(14.1) to ^{8}Be_{g.s.} lead to an assignment of J^{π} = 4^{+} for that state (1977MC07); see also (1978RI03). States at E_{x} = 7.65, 9.64, 10.84 and 14.08 MeV were observed along with a new state at E_{x} = 22.4 ± 0.2 MeV (2014MA37); the angular correlations of breakup αparticles indicate a J^{π} = 5^{} assignment for the later. A ground state rotational band including ^{12}C*(0[J^{π} = 0^{+}], 4.44[2^{+}], 9.64[3^{}], 14.08[4^{+}] and 22.4[5^{}]) is suggested. In the region of the GDR, prominent structures are observed consisting of two ≈ 2 MeV wide peaks at 26.2 and 29.2 MeV (1987KI16: see also for a discussion of deformation parameters). J^{π} assignments have been suggested for ^{12}C states with 9.6 ≤ E_{x} ≤ 39.3 MeV on the basis of their decay into 3αparticles: see (1973JA02: E_{α} = 90 MeV). The quadrupole deformation, β_{2}, is 0.29 ± 0.02 (1971SP08), 0.30 ± 0.02 (1976PA05), 0.40 ± 0.02 (1983YA01); β_{3} = 0.24 (1973SM03), 0.23 (1977BU19) and β_{4} = +0.16 ± 0.03 (1983YA01: see also for a review of deformation parameters). In (2003JO07) β_{2} = 0.753 ± 0.049, β_{0}(7.65) = 0.187 ± 0.13, β_{3} = 0.556 ± 0.066, β_{0}(10.3) = 0.157 ± 0.011, β_{1} = 0.026 ± 0.005 deformation parameter values are deduced. In (2003JO07) strength was identified corresponding to (27 ± 5)%, (78 ± 9)%, and (51 ± 7)% of the isoscalar E0, E1, and E2 energy weighted sum rule (EWSR), respectively, with centroids of 21.9 ± 0.3, 27.5 ± 0.4, and 22.6 ± 0.5 MeV and rms widths of 4.8 ± 0.5, 7.6 ± 0.6, and 6.8 ± 0.6 MeV. Less than 7% of the E3 EWSR strength was identified. See also (1998YO02, 2008KH02) and earlier work in (1976KN05, 1978RI03, 1981EY02). Angular correlation measurements α_{1}γ_{4.4} have been carried out for E_{α} = 10.2 to 104 MeV (see 1980AJ01, 1985AJ01, 1990AJ01). Measurements of the radiative widths for ^{12}C*(7.7, 9.6) are reported in (1974CH32, 1976MA46) and 12.14 (in PDF or PS). The value for Γ_{rad} for ^{12}C*(7.65) implies a 45% faster rate for the (3α) astrophysical process (1974CH32). A detailed study of the ^{12}C*(7.65) deexcitation finds the decay is 99.1% via sequential αdecay to ^{8}Be_{g.s.} and < 0.9% via direct decay into 3αparticles (2013RA20). For cross sections analyses relevant to ^{16}O see (1990AR24, 1991DE15, 1992SA26, 1993DE03, 1996VO18, 1997AB52, 1997GO10, 1999AN35, 2000AN17, 2001BU20, 2001HU14, 2002TI03, 2004SP02, 2004SP04, 2005PA58, 2005SP06, 2006BU32, 2007FR22, 2007ST21, 2009AS01, 2009TI02, 2010KA21, 2011DU06, 2011IR01, 2011SP03, 2012CU04, 2012DE08, 2012SO20, 2013CU04, 2013DE03, 2013GA05, 2013KA03, 2014CH06, 2015IR01, 2015SH22). For reaction (b) and αcluster knockout studies see (1999NA05, 1999ST06, 2007FR22, 2012CU04, 2012SO20, 2013CU04: exp.) and (2008JA02, 2009JA07, 2011CO10, 2014JA07: theory).
Angular distributions of elastic scattering have been measured at E(^{6}He) = 5.9 to 492 MeV; see 12.36 (in PDF or PS). At E(^{6}He) = 10 MeV (1995WA01) the elastic angular distribution was found to fall off more quickly than expected when compared with the Rutherford cross section; on the other hand, measurements at E(^{6}He) = 38.3 and 82 MeV/A found an enhancement of cross section at angles larger than about 15° (2002LA20, 2011LO07). At E(^{6}He) = 30 MeV, scattering to ^{12}C*(0, 4.4) was measured and analyzed for θ_{cm} ≈ 20°  100° using a coupledchannels approach (2014SM01). The nuclear forward glory effect was studied at E(^{6}He) = 5.9 MeV in (1998OS02, 1999OS04, 2002OS04), and the analysis indicated the low ^{6}He binding energy leads to a loss of flux from the elastic channel, even at very forward scattering angles. See theoretical analyses in (1993GO06, 1995GA24, 1998TO05, 2000BO45, 2000KR13, 2000MI36, 2002AB16, 2002SU18, 2003AB26, 2003LE25, 2003ZA15, 2004AB12, 2004AB13, 2004MA57, 2005AL18, 2005MI29, 2007RO29, 2008BO19, 2008DE38, 2008EL03, 2008KE06, 2008RO16, 2009DO20, 2009KU25, 2010AY08, 2010DEZW, 2010LA09, 2010LU08, 2010MA61, 2011BA03, 2011LU14, 2012AL24, 2012GI01, 2014KU09, 2015IS03, 2016IB01, 2016SU13).
See 12.37 (in PDF or PS) for a summary of reported measurements on ^{12}C(^{6}Li, ^{6}Li) and ^{12}C(^{6}Li, dα). The inelastic angular distributions to ^{12}C*(4.4, 7.7, 9.6) have been used to obtain deformation parameters (1996KE09); see earlier work in (1994RE15, 1974BI04). Measurements of large angle scattering are reported in (1996GA29, 2004CA46) and analyzed in (1990DA23, 1990SA05, 1993GO06, 1995GA22, 2003LE25, 2005MI29, 2012CA21). A method for determining nuclear radii of excited states, such as ^{12}C*(7.65. 9.64, 9.9, 10.3, 10.84), is suggested in (2009DA22). A study of the E0 strength distribution determines 10%, (5 ± 1)% and (5 ± 2)% of the EWSR, respectively for ^{12}C*(7.7, 10.3) and for 19 < E_{x} < 21.5 MeV (1987EY01). See general theoretical analyses in (1990KA14, 1991BO48, 1991EV04, 1991SA26, 1992GA17, 1994NA03, 1994SA10, 1994SA33, 1994SK04, 1995BE60, 1995EM03, 1995GA24, 1995KH03, 1995MO28, 1996CA01, 1997SA57, 1997ZE04, 1998PI02, 1999BE59, 2000BE49, 2000EL11, 2000MI36, 2002EL01, 2002EL10, 2003ZA15, 2004EL02, 2005AL18, 2006DA05, 2008KE06, 2009DA22, 2011PA37, 2013BA13, 2015AY05, 2016CA36). At E(pol. ^{6}Li) = 30 MeV the angular distributions and polarization observables corresponding to ^{12}C*(0, 4.4, 9.64) have been studied (1994RE01, 1994RE15); see also E(pol. ^{6}Li) = 50 MeV measurements to ^{12}C*(0, 4.4, 7.65, 9.64) reported in (1995KE10, 1996KE09) and theoretical analyses given in (1990FI12, 2011BA23, 2011PA37). At E(^{6}Li) = 60 MeV reaction (b) takes place via ^{12}C*(0, 4.4, 7.7) (1982AR20) and can involve structures in ^{16}O. See other measurements and analysis of the ^{6}Li breakup mechanism in (2000SC11, 2004SO23: exp.) and (1991EV04, 1991EV05). See 12.37 (in PDF or PS) for a summary of reported measurements on ^{12}C(^{7}Li, ^{7}Li). Analyses of elastic scattering distributions are given in (1991BO48, 1994SK04, 1997BE05, 2000EL11, 2002EL01, 2004EL02, 2005AL18, 2011BA23, 2014PI02) At E(pol. ^{7}Li) = 34 MeV the angular distributions and polarization observables corresponding to ^{12}C*(0, 4.4, 7.65, 9.64) and ^{12}C*(0, 4.4) + ^{7}Li*(0.48) have been studied (2000BA75, 2002KE04); see other results in (2001BA29, 2001BA57, 2006MO24) and (2011BA23: theory). For fusion and yield measurements see (2007PA33). For the ^{6}Li and ^{7}Li + C interaction cross sections at 790 MeV/A see (1985TA18).
Angular distributions for elastic and inelastic scattering have been measured at E(^{7}Be) = 8 to 280 MeV; see 12.36 (in PDF or PS). See theoretical analyses and discussion in (1995FA17, 1996KN05, 1997KN07, 2006DA05, 2010HO08). Reaction cross sections and interaction cross sections are reported at E(^{7}Be) = 245 and 420 MeV (1999FU08) and 280 MeV (1995PE09). See also (1993FE12, 2000AB31, 2002AB16).
Angular distributions for elastic and inelastic scattering have been measured at E(^{8}Li) = 13 to 24 MeV; see 12.36 (in PDF or PS). See theoretical analyses and discussion in (2014AY05). Reaction cross sections and interaction cross sections are reported at E(^{8}B) = 30 to 110 MeV (2014FA18, 2015FA03). See also (2000AB31, 2000BH09, 2001BH02, 2002AB16, 2002WA08, 2003WE07, 2004KH06, 2006SH20).
Angular distributions for elastic and inelastic scattering have been measured at E(^{8}B) = 25.8 to 320 MeV; see 12.36 (in PDF or PS). See theoretical analyses and discussions in (1995FA17, 1996AL13, 1996KN05, 1997KN07, 2000BO45, 2006DA05, 2006DA27, 2010HO08). Reaction cross sections and interaction cross sections are reported at E(^{8}B) = 206.4 MeV (2011BA25), 280 and 480 MeV (1999FU08), 288 MeV (2015JI07), 320 MeV (1995PE09) and 616 MeV (2003EN05). See also (1998KN03, 2000AB31, 2001LE21, 2002AB16, 2002PA51, 2004EV02, 2006HU12, 2006TR07, 2011HA38).
Angular distributions for elastic scattering have been obtained at E(^{9}Be) = 3 to 158.3 MeV; see recent studies listed in 12.36 (in PDF or PS). At E(^{9}Be) = 158.3 MeV angular distributions to ^{12}C*(0, 4.4) were measured by (1984FU10), and at E(^{12}C) = 65 MeV angular distributions to ^{12}C*(0, 4.4, 7.7, 9.6) were measured by (1985GO1H). Excitation functions were measured for elastic scattering at E_{lab} = 13 to 21 MeV (2011OL01) and for elastic and inelastic scattering to ^{9}Be*(2.43) or ^{12}C*(4.44) at E_{cm} = 2 to 16 MeV (1995CA26); analysis indicated significant components of ^{3}He transfer in the reactions (1995CA26); see also (1998GR21). The interaction cross section of ^{9}Be ions on ^{12}C at 790 MeV/A is reported in (1985TA18). See estimates of the total reaction cross sections for E(^{9}Be) = 3 to 26 MeV (2011ZA05); also see (1993FE12, 2000BH09, 2002AB16, 2002BR01, 2003CA07, 2006SH20, 2008KO29, 2013YA01, 2016TR10). For fusion and yield measurements see (1978CH02, 1981JA09, 1982DEZL, 1982HU06, 1983JA09, 1985DE22, 1992FI04, 1998CA27).
Angular distributions of ^{10}Be and ^{11}Be elastic scattering are summarized in 12.36 (in PDF or PS). For theoretical analyses, see (^{10}Be: 1999BR09, 2000AB31, 2009RO31) and (^{11}Be: 1995EV01, 1996EV01, 1996VO04, 1997AL05, 1997JO16, 1998TO05, 1999BR09, 1999FO13, 2000BO45, 2000JO21, 2002AL25, 2002BO25, 2002SU18, 2002TA31, 2003TA04, 2005BA72, 2005TA34, 2009HA18, 2010LA09, 2011OG09, 2011OG10, 2015IS03, 2015LU04). The interaction cross section of ^{10}Be ions on ^{12}C at 790 MeV/A is reported in (1985TA18). See estimates of the total reaction cross sections for E_{cm} = 12.7 MeV (2011ZA05); see also (1993FE12, 1996AL24, 2000BH09, 2002AB16, 2002BR01, 2006SH20). For ^{11}Be (reaction (b)), see measurements on the reaction cross sections in (1991FU10) and see other theoretical analyses in (1993FE02, 1993MA25, 1994SA30, 1996AL13, 1997FO04, 2000BH09, 2002BR01, 2003CA07, 2006GO05, 2006SH20, 2007SH33, 2008AL06, 2013SH17).
Angular distributions in reaction (a) have been measured at E_{cm} = 3.18 to 6.82 MeV (1977HI01) and at E(^{10}B) = 18 (1969VO10, 1988DI08) and 100 MeV (1977TO02). The ^{11}B + ^{12}C reaction has been studied for E(^{11}B) = 10 to 100 MeV and for E(^{12}C) = 15 to 87 MeV; see 12.36 (in PDF or PS), 12.20 (in PDF or PS) in (1985AJ01), 12.20 (in PDF or PS) in (1990AJ01) and discussion in (1980AJ01). Proton spectroscopic factors for elastic transfer reactions ranging from C^{2}S = 2  5.6 have been deduced from measurements at E_{cm} = 15 to 40 MeV (1991AL12), and 2.15 ± 0.23 was deduced at E(^{11}B) = 50 MeV (2014LI49). Spectroscopic factors for ^{12}C*(0, 4.4, 9.64) from analysis of measurements at E(^{12}C) = 18 MeV (2014HA34) and E(^{12}C) = 344.5 MeV (1990JA12, 1992JA12) are given in 12.38 (in PDF or PS). See other analyses in (1990KA17, 1998KH16, 2001RU14, 2003ME36). For fusion and yield studies see references in (1985AJ01, 1990AJ01) and (1993HA14, 1994BA41, 1996JA12, 1996KI17, 1999CA50, 2000TAZK, 2006JI01, 2009JI04).
Angular distributions for elastic and inelastic scattering have been measured at E(^{11}Li) = 550 to 660 MeV; see 12.36 (in PDF or PS). See theoretical analyses and discussion in (1991CA14, 1992TA16, 1992YA04, 1993DA09, 1993ME02, 1993TH01, 1994AL02, 1994CA07, 1994HU04, 1994SA16, 1995AL01, 1995AL02, 1995CO01, 1995DA04, 1995EV03, 1995FA17, 1995FO08, 1995GA24, 1995HU08, 1995KH11, 1996CA01, 1996KH03, 1996KN05, 1996RA18, 1996UE01, 1996UE07, 1997CH32, 1997KN07, 1997MO42, 1998CH18, 1998MO27, 1999MO37, 2000MO34, 2000PA14). Reaction cross sections are reported at E(^{11}Li) = 341 and 451 MeV (2013MO21). See other theoretical analyses mainly related to the ^{11}Li density distribution and structure in (1992OG02, 1992YA02, 1993FE02, 1993MA17, 1993MA25, 1996AL13, 1996AL24, 1996BU09, 1997FO04, 1997ZA08, 1998BE09, 1998GA37, 1998KN03, 2000BO45, 2001BH02, 2001OG10, 2002WA08, 2004CA18, 2004LO12, 2007AL07, 2007SH33, 2008CA08, 2009SH25, 2011IB02).
Angular distributions have been measured at E(^{12}C) = 10 to 2400 MeV: see 12.39 (in PDF or PS). See analyses of elastic and inelastic scattering at E < 100 MeV (1990DE13, 1991AL03, 1991TR03, 1991VE02, 1992AP01, 1994AP01, 1995AP01, 1995LI27, 1997AP06, 1997BR05, 1998AP03, 2000EB03, 2001BO18, 2001BO41, 2001EL08, 2002BO17, 2003AL17, 2005ER05, 2006KU06, 2011HA36), at E = 100 MeV to 1 GeV (1990JA12, 1990WA01, 1991AL16, 1992AY03, 1992GA08, 1992KA36, 1992LE02, 1993LI13, 1993MC01, 1994KH02, 1995FA17, 1996BE25, 1996EL05, 1997BR04, 1997BR30, 1997CH48, 1997IN02, 1997KH04, 1997KN07, 1997SI21, 1997ZE04, 2000KH06, 2000KI05, 2001FA24, 2002AH05, 2002BO58, 2002YA15, 2004AH11, 2005AL18, 2005CH48, 2007KI19, 2010BA45, 2012FU04, 2012FU09, 2013FU01, 2013WE05, 2016MI03), and at E > 1 GeV (1990AL10, 1990AM02, 1990DA12, 1990DA23, 1991CE09, 1991ZH20, 1992CH30, 1993CE01, 1994CH35, 1994GU20, 1995BE26, 1995GA24, 1996FA08, 1998CH18, 1998EL14, 1999MA18, 2000AB31, 2000EL03, 2001LU09, 2002AB16, 2002AH02, 2002FA10, 2002VA17, 2003BE31, 2004FA08, 2004GH02, 2006CH45, 2007CH42, 2009FU11, 2012GI01, 2013WE05, 2014MI22, 2016FU13). See also (1991PU01, 1991SA29, 1996AD04, 1996RA25, 1997AB50, 2007CH62, 2011FU16, 2012FU04). For comments on "rainbow" scattering and Airy minima see (1991BR04, 1992MC07, 1995GA22, 2000ME04, 2000ME05, 2002KI15, 2003SZ12, 2004KI13, 2004MI12, 2010DE32, 2010FU12, 2016KH09). The nuclear sizes of ^{12}C*(0, 4.4, 7.65) were determined by a Frauenhofer analysis of the small angle diffraction pattern at E(^{12}C) = 121.5 MeV; results indicate R_{diffraction} = 6.35 ± 0.09, 6.26 ± 0.10 and 6.86 ± 0.11 fm, respectively (2011MA04). See also (2009DA22), who evaluated ^{3}He, α, ^{6}Li and ^{12}C scattering data, deduced the diffractive radii for ^{12}C*(0, 4.4, 7.65, 9.64) and deduced R_{rms} = 2.34, 2.36 ± 0.04, 2.89 ± 0.04, 2.88 ± 0.11 fm for those states, respectively. The relative population of elastic and inelastic channels is very energy dependent, for example, because of structure effects and molecularlike states in ^{24}Mg; see references listed in (1975AJ02, 1980AJ01, 1985AJ01, 1990AJ01), and see footnote ^{a} in 12.40 (in PDF or PS). The spin alignment of ^{12}C*(9.64) was studied in (1993DA22, 1995DA05) and shows little energy dependence. See also (1990SA07, 1990SA48, 1992GR15, 1992RA25, 1993AB05, 1993ME04, 1994AD13, 1994ME18, 1994SA07, 1995BE33, 1995HI21, 1996AD04, 1996SC02, 1998KO29, 1999IT02, 2000SA57, 2001BO18, 2002IT05, 2003SA36, 2003SA39, 2003SZ12, 2005GA33, 2006PE23, 2007FR22). For reaction (b), several states are observed by reconstructing the complete kinematics of decay α particles, see 12.40 (in PDF or PS). In (2007FR17), the threeα breakup systematics are analyzed to determine spin values for states with E_{x} ≥ 7.65 MeV; the analysis found no evidence for the J^{π} = 2^{+} excitation of the Hoyle state that is expected near 10 MeV. Contradictory results for previous J^{π} value assignments for states such as ^{12}C*(11.83, 13.35) were also found along with suggestive evidence for new broad states nears E_{x} = 11.8 and 12.5 MeV. In (2007FR17) analysis of the E_{x} = 11.16 MeV region is given that showed limited evidence for a previously accepted state; however, in light of the findings in (2012SM06), the result of (2007FR17) does not provide sufficient evidence for the state's existence (private communication, M. Freer, June 2017). In (2010MU05) analysis of the αparticle angular correlations found no evidence for excess J^{π} = 2^{+} strength in the E_{x} ≈ 9 to 10 MeV excitation region. In (1991CA01) no evidence for direct 3αdecay was observed from any state. Detailed measurements of the ^{12}C*(7.65) decay systematics, which are relevant for astrophysical ^{12}C formation, are given in (1994FR05, 2014IT01); see also (1996RA08). In (2014IT01) the decay kinematics of ^{12}C*(7.65) are analyzed, and the results are consistent with 100% sequential decay via ^{8}Be_{g.s.}, with limits of < 0.2% decay via 3body phase space and < 0.08% decay into 3 equal energy α particles. The αα correlation data is analyzed in (2007FR05), and discussion relating the correlations to the nuclear radii of excited states is given.
Elastic and inelastic angular distributions are reported at E(^{12}C) = 127.2 MeV (2010AL10) and E(^{13}C) = 16.3, 20, 29.5 MeV (1995LI23) and 240 MeV (2010DE32). See previous measurements reported at E(^{12}C) = 15 to 36 MeV and 87 MeV (1975AJ02), at E(^{12}C) = 20 to 35 MeV and E(^{13}C) = 12 and 36 MeV (1980AJ01), at E(^{12}C) = 15 MeV and E(^{13}C) = 87 MeV (1985AJ01), and at E(^{12}C) = 94.5 MeV and E(^{13}C) = 16.3 to 26.5 MeV, 36 MeV and 260 MeV (1990AJ01). The spinflip probability to ^{12}C*(4.4) has been studied at E(^{13}C) = 36 and 56 MeV by (1985BY01); also see (1981TA21). The mirror scattering reactions of ^{12}C + ^{13}C and ^{12}C + ^{13}N are compared in (1995LI10, 1995LI23, 1997IM01). Rainbow scattering and Airy minima are discussed in (2003BE70, 2004BE42, 2010DE32, 2015OH02). See also (1990BA03, 1993IM02, 1999RA24, 2010AL10). For reaction (b) elastic angular distributions are reported at E(^{12}C) = 12 to 20 MeV (1972BO68) and E(^{14}C) = 31.0 to 56 MeV (1985KO04). Excitation functions to ^{26}Mg resonances are studied for ^{12}C(^{14}C, ^{14}C) at E_{cm} = 22 to 30 MeV (1992FR13) and E_{cm} = 6 to 35 MeV (2003SZ11).
Elastic and inelastic scattering has been measured at E(^{13}N) = 16.3, 20 and 29.5 MeV (1995LI10, 1995LI23) and at 153.4 MeV (2004TA15). The ^{12}C + ^{13}C and ^{12}C + ^{13}N systems appear to comply with charge symmetry, see (1995LI10, 1995LI23, 1997IM01).
This reaction has been used to populate ^{12}C^{12}C quasimolecular states in ^{24}Mg, see for example measurements at E(^{14}N) = 30 to 45 MeV (1994ZU03) and analyses in (1994BE55, 1999SA54, 2002BE71, 2002BE73).
Elastic and inelastic angular distributions are reported at E(^{14}N) = 80.73, 100.3 MeV (1990DE13), 116 MeV (1997ZI05) and 280 MeV (1990BR21). See previous measurements reported at E(^{14}N) = 21.5 to 27.3 and 62.5 MeV (1968AJ02), E(^{14}N) = 21 to 155 MeV (1975AJ02), E(^{14}N) = 37 to 155 MeV (1980AJ01), E(^{14}N) = 48 to 78 MeV (1985AJ01) and E(^{14}N) = 150 MeV (1990AJ01). At E(^{14}N) = 155 MeV ^{12}C*(0, 4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 13.4, 14.1) are reported; see (1975AJ02). Highenergy γray emission has been studied at E(^{14}N) = 280 to 560 MeV (1986ST07). See also (1994AD08, 1997IN02, 2003AU04). For reaction (b), angular distributions are reported at E(^{15}N) = 31.5 to 47 MeV (1978CO20) and the spinflip probability to ^{12}C*(4.4) has been studied at E(^{15}N) = 94 MeV (1981TA21).
The angular distribution for quasielastic scattering at E(^{16}C) = 47.5 MeV/A is reported for θ_{cm} = 5 °  40° (2009FA07).
Angular distributions involving ^{12}C and ^{16}O states have been measured at E(^{16}O) = 17.3 to 1503 MeV and at E(^{12}C) = 65 to 76.8 MeV: see 12.41 (in PDF or PS). See general analyses in (1990DA12, 1991ST07, 1992CH29, 1992CO01, 1993MA09, 1994KH02, 1994SA24, 1996EL05, 1997BR04, 1997CH23, 2000EL03, 2000KI30, 2000ME04, 2002AN35, 2002KU41, 2003BE31, 2005CH48, 2005KO52, 2006HO04, 2007GO35, 2009CH46, 2009FU11, 2011GR11, 2011MO07, 2012FU04, 2012GR16, 2013GR13, 2014FA04, 2014FA11, 2016FU13, 2016MA52). The reaction dynamics leading to the Airy patterns at large scattering angles are discussed in (1997RI08, 2001AN04, 2001GO46, 2001MI06, 2002MI19, 2002MI39, 2002SZ03, 2003GO34, 2003OG04, 2003SZ12, 2008GR12, 2008GR14, 2008KO16, 2009KO05, 2010BA45, 2010DE10, 2014OH02, 2015MA12, 2016HA01). In (1979DO01) excitation of the giant quadrupole resonance is observed in groups at ^{12}C*(25.3, 26.7) with Γ ≈ 4 MeV that contain (25^{+15}_{10})% of the energyweighted E2 sum rule strength; states at ^{12}C*(0, 4.4, 9.6, 10.8, 15.8, 21.6) were also populated. For fusion resonant excitation function studies to states in ^{28}Si see (1992SA21, 1993BE17, 1993ES01, 1994GA06, 1995BU29, 1995FR12, 1995SI13, 1997FU12, 1997GY02, 1998KE02, 2008LE27, 2011LE19, 2011CO05, 2012RU02, 2012LE04, 2013KU04, 2014KU06, 2014GO03) and (1994GR26, 2004KO38, 2007FR22: theory). For studies of other nuclides see (^{20}Ne: 1994RA04, 1995SU06), (^{24}Mg: 1991CO09, 1994CO01, 1994KU18, 1995FR12, 1997FU12, 1998FR03, 2001FR19, 2001TU06, 2001WI18, 2011JO02, 2012DI04 and theory: 2007FR22) and (^{26}Al: 1993BE17, 1997BA51, 1998BA19). See also (1993HA14, 1993WA16, 1994CZ03, 1994DE21, 1995SC30, 2006YA14, 2007GA43, 2009CH35, 2009LO01, 2012UM02, 2015AB01). For discussions on fragmentation reactions see (1990WE15, 1992MA13, 1992ME02, 1999BO46, 2000CH20, 2000FA12, 2001DE50, 2002MO22, 2008KU15, 2011DE09).
Elastic and inelastic angular distributions are reported at E(^{17}O) = 22 to 38 MeV (1993TI05) and E(^{18}O) = 66 to 120 MeV (2001SZ05, 2006SZ06), 84 MeV (2011CA33), 94.5 MeV (2009AD08), 105 MeV (2010RU03, 2010RU13, 2010RU15, 2011RU07) and 216 MeV (2014AL05, 2014AL11). See previous measurements reported at E(^{17}O) = 35 MeV (1975AJ02), 30.5 and 33.8 MeV (1980AJ01), 40 to 70 MeV (1990AJ01), and E(^{18}O) = 35 MeV (1975AJ02), 32.3, 35, 47.5, 55 and 57.5 MeV (1980AJ01) and 32.0 to 140 MeV (1985AJ01). Fusion yields and other reactions to isotopes in, for example, Ne and Si are reported in (1990XE01, 1993BE17, 1993TI05, 1996FO16, 1999BO46, 2000CH20, 2000FA12, 2006FR16, 2006YI01, 2011BA22, 2011GI03, 2014ST22) and (1980AJ01, 1985AJ01, 1990AJ01). See also analyses in (1991TH02, 1991TH04, 1997KI22, 1999MA96, 2002BR01, 2004KH06, 2006BH01, 2008KO29, 2009AB07, 2011KU06, 2011SH26, 2012HO19, 2012RA29, 2014HO02).
Angular distributions for elastic scattering and quasielastic scattering have been measured at E(^{17}F) = 60 MeV (2012ZH21) and 170 MeV (2005BL23). For reaction (b), elastic scattering and fusion angular distributions are reported at E(^{19}F) = 10 to 16 MeV (1990XE01), 19 to 56 MeV (1999CA50), 22 to 24 MeV (2004SU02), 48 to 72 MeV (2002AN11), 57 to 64 MeV (2002SU17), 83.6 MeV (2003WO17, 2004KI07, 2006WO04), 92 MeV (1997AI01, 1997AI06), 96 MeV (1996BH06, 1999BA11, 2001BB02, 2002BA50), 111 to 136.9 MeV (1997PO07, 2001PO01), 121.7 MeV (1995VA05) and 912 MeV (2001ME26). See previous measurements reported at E(^{19}F) = 40, 60 and 68.8 MeV (1975AJ02), E(^{19}F) = 18.0 to 60.1 MeV (1985AJ01) and E(^{19}F) = 29.3 to 60.1 MeV (1990AJ01). The substate population probability for ^{12}C*(4.4) has been studied by (1986IKZZ) at E(^{19}F) = 63.8 MeV.
Elastic angular distributions are reported at E(^{20}Ne) = 390 MeV (1993BO28) and E(^{22}Ne) = 264 MeV (2010AL10). See previous measurements for reaction (a) reported at E(^{20}Ne) = 65.7 MeV (1980AJ01) and at E(^{12}C) = 37 MeV (1975AJ02), 20 to 34.4, 60.7, 72.6 to 75.2 MeV [to ^{20}Ne*(0, 1.6)] and 77.4 MeV (1985AJ01). Fusion to sulfur, reaction cross section, fragmentation yield and evaporation residue studies are also reported in the literature. See also (1990SL01, 1997BR05, 1997FR04, 2004FA08, 2007FR22).
Elastic angular distributions are reported for reaction (a) at E(^{12}C) = 19, 21 and 23 MeV (1993LE08), 32 to 48 MeV (1997SC14), 85 MeV (2000SI36) and 104 MeV (2017JO03), and at E(^{24}Mg) = 130 MeV (2004BE08, 2004BE18, 2009BE34) and 768 MeV (2001CH11, 2001CH56). See previous measurements for reaction (a) at E(^{12}C) = 20 to 36, 20 to 60, 24.8, 27.7 to 34.8 and 40 MeV (1985AJ01) and for reaction (b) at E(^{12}C) = 20 to 56 MeV (1985AJ01). The B(E2) values and deformation parameters for the first J^{π} = 2^{+} states of ^{24,30,32}Mg are measured at E ≈ 32 MeV (2001CH11, 2001CH56). See also analyses of scattering distributions given in (1991LI34, 1992GR15, 1994LI33, 1996FR23, 1997FR04, 1999KU01, 1999LE14, 1999LE38, 1999LI34, 2000LU03, 2001BO41, 2001BO46, 2001KU01, 2002BO17, 2002BO58, 2002KU33, 2004BE31, 2005BO28, 2005BO31, 2006KA23, 2006KA43, 2006MA33, 2007FR22). Reaction induced fission of ^{24}Mg to ^{12}C^{12}C cluster states is studied at E(^{24}Mg) = 170 and 180 MeV (1991BE27, 1991FU03, 1991FU09, 1994CU05, 1995CU01, 1995LE22, 2000CU02, 2001SH08) and E_{cm} = 43.3 to 60 MeV (1994GY01). Studies on fusion to ^{32}S and ^{36}Ar, fragmentation yields, and other reaction cross sections can be found in the literature.
Elastic angular distributions have been measured at E(^{12}C) = 21 MeV (2011HA47) and 30.0 to 39.9 MeV (1979RO11), while that of the transition to ^{12}C*(4.4) has been studied at E(^{12}C) = 82 MeV (1977BE42) and E = 344.5 MeV (1990JA12). See also (2004FA08, 2004GA16, 2006ZA10). Results on fusion, fragmentation yield, and other reaction studies are found in the literature.
Elastic scattering for reaction (a) was studied at E(^{12}C) = 60, 65, 75 and 85 MeV (1998YA02) and E(^{28}Si) = 145 and 160 MeV (1991RA05). See previous measurements at E(^{12}C) = 19 to 36, 24, 27, 30, 40.2, 49.3, 70 and 83.5 and 186.4 MeV and at E(^{28}Si) = 58.3 to 116.7 MeV see (1980AJ01), at E(^{12}C) = 19 to 48, 41.3, 56.0 to 69.5 and 131.5 MeV see (1985AJ01), and at E(^{12}C) = 56, 59, 66, 69.5 and 65 MeV see (1990AJ01). The αγ angular correlations have been studied at E(^{28}Si) = 112.3 and 142.7 MeV: ^{12}C*(4.4) is found to be produced almost entirely in the m = 0 magnetic substate (1986RA08). Elastic and inelastic scattering on ^{29}Si was studied at E(^{12}C) = 36.8 MeV (1968AN21). See theoretical analysis of elastic scattering on ^{28}Si in (1992GR15, 1997CH41, 1999LE14, 1999LE38, 1999RA24, 2001EL08, 2004PA17, 2010BA45) and see specific discussion on "forward glory" scattering in (2000DA15, 2003LE25, 2004DA27, 2011DA04). Results on fusion, fragmentation yield, and other reaction studies on ^{28,29,30}Si targets are found in the literature.
Elastic and inelastic angular distributions and B(E2) values are reported at E(^{32}S) = 65 to 67 MeV (2006SP01). See previous measurements at E(^{12}C) = 35.8 MeV and E(^{32}S) = 73.3 to 128.3 MeV (1980AJ01), E(^{32}S) = 60 to 99 MeV and 160 MeV (1985AJ01), and E(^{32}S) = 194, 239 and 278 MeV (1990AJ01). See also (1990ME07, 1991AR15, 1991BE27, 1991FI04, 2001PI10, 2003BE75), references in (1980AJ01, 1985AJ01, 1990AJ01) and other references in the literature for discussion on fusion, fragmentation yield and other reaction studies.
Elastic angular distributions for reaction (a) have been studied at E(^{12}C) = 54 and 63 MeV (1980GL03). For reaction (b) see measurements in (1989PL02, 1990LE08, 1990LE10, 1991PA08, 1993YO03, 2004MO48).
The elastic scattering in all three reactions has been studied at E(^{12}C) = 51.0, 49.9 and 49.9 MeV, respectively (1979RE03) and for reaction (a) at E(^{12}C) = 180, 300 and 420 MeV (1986SA29). See theoretical analysis of elastic scattering on a ^{40}Ca target in (1994SA37, 2003AL17, 2008KI20, 2013XU06). Results on fusion, fragmentation yield, and other reaction studies are found in the literature.
^{12}N decay to ^{12}C is complex. Most of the decay populates ^{12}C_{g.s.} with small branches populating ^{12}C*(4.4) and several αparticle unbound states (see 12.42 (in PDF or PS)). The ground state decay branch is determined by subtracting all other observed decay branches from unity. Early studies were motivated by evaluation of the ^{12}B and ^{12}N mirror decays to states in ^{12}C and by parity violation studies. The decay rates to ^{12}C*(4.4) measured in (1981KA31) are most precise and have been used as normalization factors in modern experiments to deduce the relative and absolute branching ratios of weaker decay branches, see 12.23 (in PDF or PS). In most articles, measurements on ^{12}N and ^{12}B were published together; see reaction 32 ^{12}B β^{}decay for detailed discussion on the experiments. Studies on ^{12}N decay are more complicated than those on ^{12}B decay because the highenergy 17.3 MeV β^{+} particles can produce Bremsstrahlung photons while interacting in the βcounter, which can be detected in the γcounter giving rise to a huge background under the discrete photopeaks. The Qvalue for ^{12}B decay is 13.37 MeV, which leads to a significantly lower background radiation. In addition, the β^{+} annihilation photons can sum with decay γrays in the detector causing a distortion away from the expected response function. Discussion on systematic effects is given in (1974MC11, 1978AL01). A detailed study of the highenergy portion of the γray spectrum identified decay branches populating the ^{12}C*(12.71, 15.11) states (1967AL03). The βγ spectra were analyzed to determine the ratios I(E_{γ} = 12.72)/I(E_{γ} = 4.4) = 2.9 × 10^{3} ± (26%) and I(E_{γ} = 15.11)/I(E_{γ} = 4.4) = 1.78 × 10^{3} ± (20%). Using the known Γ_{γ} and γdecay branching ratios the βdecay intensities to these states can be deduced. Interest in the higherlying J^{π} = 0^{+} and 2^{+} states led to measurements where ^{12}N and ^{12}B ions were produced at rare isotope facilities. Analysis of these data gave precise details on the α breakup channel for ^{12}C states up to E_{x} = 15.11 MeV populated in the decays, see for example (2004FY03, 2005DI16, 2009DI06, 2014TE01). In (2009HY01, 2009HY02, 2010HY01) it is found that interference of the J^{π} = 0^{+}_{2} state with other J^{π} = 0^{+} strength around E_{x} ≈ 11.2 MeV leads to "the very broad component from 8.5 to 11 MeV, which has been mistaken for a 10.3MeV resonance with a 3MeV width". Rather than attribute their observed strength to a 10.3 MeV group, they provided the β feeding strength for the E_{x} = 912 MeV and 1216.3 MeV regions [excluding the 12.7 MeV state]. A multilevel manychannel Rmatrix analysis of the data (2010HY01) indicated a J^{π} = 0^{+} state at E_{x} = 11.2 ± 0.3 MeV with Γ = 1.5 ± 0.6 MeV and B(GT) = 0.06 ± 0.02 and a J^{π} = 2^{+} state at E_{x} = 11.1 ± 0.3 MeV with Γ = 1.4 ± 0.4 MeV and B(GT) = 0.05 ± 0.03.
The βdecay of ^{13}B primarily populates bound states in ^{13}C with an intensity > 99%. However weak decay branches to ^{13}C*(7.54, 8.86, 9.90) and possibly ^{13}C*(9.50) lead to βdelayed neutron emission to ^{12}C*(0.4.4) with P_{n} = (0.28 ± 0.04)% (1962MA19, 1969JO21, 1974AL12); see Fig. 4 [^{13}B β^{}ndecay scheme].
The decay of the giant resonance in ^{13}C takes place predominantly to ^{12}C*(15.1, 16.1) [and to their analogs in ^{12}B]. Below E_{γ} = 21 MeV transitions to ^{12}C*(4.4) are dominant (1975PA09). A review on isospin component splitting in ^{13}C up to E_{γ} ≈ 30 MeV is given in (1993MC02).
The neutron decay of the pygmy and giant dipole resonances of ^{13}C were studied using E_{e} = 129 MeV electron scattering (1999SU12). Neutron decay from the pygmy resonance tends to populate ^{12}C*(0, 4.4), while neutron decay from the GDR tends to populate ^{12}C*(12.7, 15.11).
Angular distributions have been measured at E_{π+} = 90 to 170 MeV to ^{12}C*(0, 4.4, 7.7, 9.6, 12.7, 14.1, 15.1, 16.1, 19.1, 20.6, 22.9, 25.3) (1981AN10): an energy dependent ratio for the excitation of ^{12}C*(12.7, 15.1) is reported along with similarities in the population of states seen in this reaction and in the (p, d) reaction. Angular distributions are reported to ^{12}C*(0, 4.4) at E_{π+} = 32 MeV (1982DO01). The population of ^{12}C*(4.4) is more than 10 times that of ^{12}C_{g.s.}.
Angular distributions have been measured at E_{p} = 8 to 800 MeV; see (1995TO03) for E_{p} = 35 MeV to ^{12}C*(0, 4.4), see (1982BU03) for E_{pol. p} = 123 MeV^{†} to ^{12}C*(0, 4.4), see (1990AJ01) for E_{p} = 18.6 MeV^{†} to ^{12}C*(0, 4.4), 41.3 MeV to ^{12}C*(0, 4.4, 12.7, 15.1, 16.1), 800 MeV to ^{12}C*(0, 4.4, 12.7, 14.1, 15.1, 16.1) and E_{pol. p} = 119 MeV^{†} to ^{12}C*(0, 4.4, 7.7, 9.6, 12.7, 14.1, 15.1, 16.1, 16.6, 17.8, 18.16 ± 0.07, 18.8, 19.9, 20.3, 20.6) and 500^{†} MeV to ^{12}C_{g.s.}, see (1985AJ01) for E_{p} = 800 MeV to ^{12}C*(0, 4.4, 12.7, 14.1, 15.1, 16.1) and E_{pol. p} = 65^{†} MeV to ^{12}C*(0, 12.7, 15.1, 16.1) and 200 and 400 MeV to ^{12}C*(0, 4.4), see (1980AJ01) for E_{p} = 16.7 and 17.7 MeV to ^{12}C*(0, 4.4) and 200 to 500 MeV to ^{12}C*(0. 4.4), see (1975AJ02) for E_{p} = 50^{†} and 54.9^{†} to ^{12}C*(0, 4.4, 12.7, 15.1, 16.1), and 62^{†} MeV to ^{12}C*(15.11, 16.1, 17.76, 18.8, 21.5, 22.55), and see (1968AJ02) for E_{p} = 8, 12 and 17 MeV to ^{12}C*(0, 4.4). Spectroscopic factors are deduced in measurements highlighted with the symbol ^{†}. See also (1990GU26, 1990MU19, 1991AB04, 2004LI41, 2005DE33, 2005TS03, 2009DE02, 2009DE07, 2009DE13, 2012KU35). The population of ^{12}C*(10.3, 15.4) is reported in (1987LE24) along with structures at E_{x} = 18.2, 18.8, 19.9, 20.3 and 20.6 MeV that have Γ_{cm} = 240 ± 50, 120 ± 30, ≈ 400, ≈ 220 and ≈ 210 keV, respectively. (1984SM04) report structures at 20.61 ± 0.04 and 25.4 ± 0.1 MeV, the latter with Γ ≥ 0.5 MeV. At E_{p} = 62 MeV, (1974PA01) report the excitation of states having widths [Γ (keV)] of E_{x} = 15112 ± 5, 16110 ± 5 [< 20], 17760 ± 20 [80 ± 20], 18800 ± 40 [80 ± 30], 21500 ± 100 [< 200] and 22550 ± 50 [< 200] keV: l_{n} = 1 for all states except ^{12}C*(21.5) and (22.55) for which l_{p} = (1) and ≠ 1, respectively. ^{12}C*(14.1) is not excited, consistent with J^{π} = 4^{+} (1970SC02, 1974PA01). For dγ correlations via ^{12}C*(15.1) see (1987CA20). For reaction (b), cross sections and angular distributions for deuterons and smallrelative angle pn pairs with small relative angles (^{1}S_{0} state pairs) were measured at E_{p} = 35 MeV (1995TO03); both angular distributions were reproduced in coupled channels calculations, and the angular distribution for the singlet state pairs was found to fall off more slowly at large angles. Also see (1996GO07). In a kinematically complete experiment at E_{p} = 7.9 to 12.5 MeV (1971OT02), it was found that sequential decay via states in ^{13}C and ^{13}N is strongly involved in the reaction. Near E_{p} = 12.5 MeV there is some indication of sequential decay via singlet deuteron formation.
Angular distributions, mainly for t_{0}, t_{1} and t_{2}, have been measured for E_{d} = 0.41 to 29 MeV. See (1985AJ01) for E_{d} = 18 MeV, see (1980AJ01) for E_{d} = 24.1, 26.2 and 27.5 MeV and E_{pol. d} = 13 and 29 MeV, see (1975AJ02) for E_{d} = 0.41 to 0.81, 1.0 to 2.7, 2.2, 3.3 8, 12, 12.1, 13.3, 13.6, 14, 14.8, 15 and 28 MeV, see (1968AJ02) for E_{d} = 2.2, 3.3, 8, 12 and 14.8 MeV. Also see analyses in (1990GU26, 1995GU22, 2007CO01). The relative yields of triton groups to ^{12}C*(12.7, 15.1, 16.1) [(J^{π}; T) = (1^{+}; 0), (1^{+}; 1) and (2^{+}; 1), respectively] and ^{3}He groups to ^{12}B*(0, 0.95) [(J^{π}; T) = (1^{+}; 1) and (2^{+}; 1), respectively] give information on a possible short range charge dependent nuclear force. Ratios were measured at E_{d} = 62 MeV (1972BR27), 24.1 to 27.5 (1977LI02) and 29 MeV (1979CO08) yielding chargedependent matrix element values of 250 ± 50 keV, 180 ± 80 keV and 120 ± 30 keV, respectively. If the j = 1/2 component is excluded, which appears to be unwarranted, the charge dependent matrix element of (1979CO08) increases to 140 ± 40 keV. For a comparison of reported chargedependent matrix element values between ^{12}C*(12.7, 15.1) see 12.18 (in PDF or PS).
Angular distributions, mainly involving α_{03} have been measured at many energies up to 60 MeV; see (1990ES01): E_{cm} = 1.05 and 1.20 MeV, (1994BU01): E(^{3}He) = 37.9 MeV, (1990MU19): E(^{3}He) = 39.6 MeV, (1992AD06): E(^{3}He) = 50 and 60 MeV, (1959AJ76): E(^{3}He) = 2 and 4.5 MeV, (1968AJ02): E(^{3}He) = 1.6 to 3.3, 1.8, 4.5, 8.8, 9.4, 10.3, 12, 15, 18, 40 to 45 MeV, (1975AJ02): E(^{3}He) = 1.5 to 5.3, 19.1, 27.3, 35.7, 36.8 MeV, (1980AJ01): E(^{3}He) = 18, 20, 29.2 MeV, (1985AJ01): E(^{3}He) = 18.3 and 23.1 MeV and (1990AJ01): E(^{3}He) = 22.7 MeV. A DWBA analysis of α_{03} and ^{12}C*(10.84, 11.8, 12.7, 13.3) distributions (1966KE08) finds l = 1 or 0 for all the groups except α_{3} (to ^{12}C*(9.6)) for which l = 2. Rainbow scattering effects are discussed in (1992AD06, 1994BU01). See also (1968AR12, 1990GU26). Angular correlations of αparticles and 4.4 MeV γrays have been studied at E(^{3}He) = 4.5 MeV (1962HO13) and 29.2 MeV (1976FU1F). For ^{12}C*(15.1), angular correlations have been studied at E = 9.4 and 11.2 MeV (1969TA09) and at E = 24 and 25.5 MeV (1980BA1U): the average ratio between the p_{1/2} and p_{3/2} amplitudes is 0.086 ± 0.030 in the later measurement; see also (1999LE48, 2003ZE06). See (1990ES01, 2007GA24) for discussion on neutron stripping and ^{9}Be cluster transfer, and see (1984VA39, 1985VA1E, 1986ZE1C) for a study of the spin tensors for ^{12}C*(4.4). Ion beam analysis of surfaces is discussed in (2017MO06). For a detailed analysis of the decays of ^{12}C*(12.7, 15.1) see (1970RE09) and 12.14 (in PDF or PS). Attempts have been made to study the T mixing between the 1^{+} states ^{12}C*(12.71, 15.11). Reported values for Γ_{α}/Γ for ^{12}C*(15.11) are (1.2 ± 0.7)% (1970RE09, 1970RE1F), (6.0 ± 2.5)% (1970AR30) and (4.1 ± 0.9)% (1974BA42). The (1974BA42) value was obtained by observing the decay αparticles (only α_{1}) in reaction (b); using the ^{12}C*(15.11) Γ_{γ0} (1983DE53) and γdecay branching ratios (1972AL03) leads to Γ_{α} = Γ_{α1} = 1.8 ± 0.3 eV. If this isospin forbidden Γ_{α} is the result of the mixing between the 1^{+} states ^{12}C*(12.71, 15.11) [T = 0 and 1, respectively] via a charge dependent interaction, the matrix element is 340 ± 60 keV (1974BA42): see, however, 12.18 (in PDF or PS) and (1980AJ01). For reaction (c), proton unbound states in ^{13}N that decay to ^{12}C*(0, 4.4, 7.65, 12.7, 14.08, 15.1, 16.1) were studied at E(^{3}He) = 450 MeV (2004FU12).
At E(^{7}Li) = 34 MeV angular distributions have been observed for the reactions to ^{12}C*(0, 4.4) + ^{7}Li*(0, 0.48) and ^{8}Li*(0, 0.95) in all combinations. While ^{12}C*(0, 4.4) are dominant in the two spectra, ^{12}C*(7.7, 9.6) and, in reaction (a) at E(^{6}Li) = 36 MeV, ^{12}C*(12.7) are also populated (1973SC26). See also (1987CO16, 2003TR04, 2004CA46).
Angular distributions have been reported at E(^{13}C) = 16.0 to 50.0 MeV by (1983KO15) who have also studied the excitation functions over that energy range. For reaction (b), (2014MC03) deduced spectroscopic factors and asymptotic normalization coefficients at E(^{14}C) = 168 MeV. See (1988BI11) for measurements at E(^{13}C) = 20.0 to 27.5 MeV.
Angular distributions for neutron exchange reactions involving oxygen isotopes are reported at E(^{16}O) = 42 to 65 MeV (1989FR04), 13 and 14 MeV (1976DU04), 14, 17 and 20 MeV (1971BA68) and 41.7 and 46.0 MeV (1973DE21); E(^{17}O) = 29.8 and 32.3 MeV (1977CH22, 1978CH16), and E(^{18}O) = 15, 20 and 24 MeV (1971BA68, 1971KN05) and 31.0 MeV (1978CH16). See also (1990IM01).
The βdecay of ^{13}O populates ^{13}N_{g.s.} in (88.7 ± 0.2)% of all decays. The levels with E_{x} ≥ 3.50 MeV decay via proton emission to ^{12}C*(0, 4.4, 7.65) leading to P_{p} = (11.3 ± 2.3)%. See (2005KN02) and Fig. 5 [^{13}O β^{+}pdecay scheme]. Also see (1965MC09, 1970ES03, 1990AS01, 2014TE01).
Angular distributions have been measured at E_{p} = 14.5 (1971CU01), 18.5 (1963LE03), 39.8 (1973HO10), 40.3 (1990YA02), 45 (1978RO08), 46 (1979FR04), 50.5 [unpublished in (1975AJ02)] and 54 MeV (1976AS01). At E_{p} = 40.3 MeV, the states at ^{12}C*(0, 4.4, 7.65, 9.64, 12.71, 14.08, 15.11, 16.10, 17.76, 18.80) are populated; cross sections for natural parity T = 0 states are enhanced when compared with the T = 1 states (1990YA02). At E_{p} = 54 MeV the first T = 2 states of ^{12}C are observed at E_{x} = 27.57 ± 0.03 and 29.63 ± 0.05 MeV [Γ_{cm} ≤ 200 keV] (1976AS01): their identification is supported by the similar angular distributions to the first two T = 2 states in ^{12}B, reached in the (p, ^{3}He) reaction [see reaction ^{14}C(p, ^{3}He) in ^{12}B]. The lower T = 2 state is well fitted by L = 0; the angular distribution to ^{12}C*(29.63) is rather featureless. It is suggested that its shape is more consistent with L = 0 than with L = 2. It is not excluded that the group to ^{12}C*(29.63) may be due to unresolved states. The states are observed with Γ_{p}/Γ = 0.3 ± 0.1 and Γ_{α1}/Γ < 0.1 for the first T = 2 state and Γ_{p}/Γ = 0.8 ± 0.2, Γ_{p0}/Γ ≈ 0.4 and Γ_{α}/Γ ≈ 0.2 for ^{12}C*(29.63). (1976BA24) has suggested that the second T = 2 state in A = 12 may have J^{π} = 0^{+}. At E_{p} = 45 MeV, (1978RO08) report E_{x} = 27595.0 ± 2.4 keV, Γ ≤ 30 keV for the first T = 2 state and calculate the decay properties for two values of the total width, narrow and 30 keV. A subsequent measurement at E_{p} = 46 MeV reported branching ratios for the decay of ^{12}C*(27.6) to ^{8}Be_{g.s.} + α; ^{11}B*(0, 2.12, 4.45, 5.02, 6.74 + 6.79) + p; and ^{10}B_{g.s.} + d are, respectively, (10.5 ± 3.0)%; (3.0 ± 2.2)%, (8.0 ± 2.3)%, (0 ± 3.3)%, (8.4 ± 3.2)%, (8 ± 5)%; and (2.8 ± 2.0)% (1979FR04). An additional (9.1 ± 3.5)% of the decay feeds into the ^{8}Be* + α continuum. See also (2006FO11).
Angular distributions of ^{3}He, mainly to ^{12}C*(0, 4.4) and also to ^{12}C*(12.7, 14.1, 15.1, 16.1), have been studied at E_{p} = 7.5 to 52 MeV; see references in (1975AJ02, 1980AJ01). At E_{p} = 50 MeV, the analysis indicates J^{π} = 4^{+} for ^{12}C*(14.1) (1970SC02). The angular distributions to the first two T = 1 states in ^{12}C are compared with those of the analog states in ^{12}N obtained in the (p, t) reaction (1976YO03). For reaction (b) the transitions to ^{12}C*(0, 4.4) have been studied at E_{p} = 46 MeV (1970WE1J, 1971WE05) and to ^{12}C*(4.4) at E_{p} = 58 MeV (1985DE17).
Alpha groups have been observed corresponding to most known ^{12}C states up to ^{12}C*(16.11), see (1965BR08, 1965SC12) and 12.34 (in PDF or PS). The reaction proceeds mainly via α_{03}. Angular distributions have been measured at several energies, see (1959AJ76): E_{d} = 10.8 to 20 MeV, (1968AJ02): E_{d} = 0.5 to 28.5 MeV, (1975AJ02): E_{d} = 1.0 to 40 MeV, (1980AJ01): E_{d} = 2.7 to 40 MeV, (2004PE10): E_{d} = 0.5 to 2.0 MeV, (2008GU08): E_{d} = 0.7 to 2.2 MeV and (1999IG03): E_{d} = 15.4 MeV. The αγ correlations give J = 2^{+} for the 4.4 MeV state (1954ST1C). At E_{d} = 1.8 MeV, the αparticles to the 7.65 MeV state were observed in coincidence with recoiling ^{12}C_{g.s.} nuclei; if Γ_{rad} = (Γ_{γ} + Γ_{π}), then the ratio Γ_{rad}/Γ = (2.8 ± 0.3) × 10^{4} was reported in (1963SE23). The width of the 9.6 MeV state Γ_{cm} is reported as 30 ± 8 keV (1953DU23, 1956AH32). Analysis of the angular distributions at E_{d} = 40 MeV, with a onestep, ZRDWBA, leads to J^{π} = (1, 2, 3)^{+}, (2, 3)^{+} and (2, 3)^{+}, respectively for ^{12}C*(19.5, 20.6, 22.5) (1976VA07); spectroscopic factors were also deduced for all observed transitions. At E_{d} = 40 MeV, the upper limits for the ratio of the cross sections to ^{12}C*(15.11) and ^{12}C*(12.71) are ≈ 0.3% for θ_{lab} = 6° to 10° and 0.5% at 40° and 50°: these results by (1974VA15) imply a lower isospin mixing between these two 1^{+} states than suggested by the work of (1965BR08, 1972BR27). See also (1991AP03, 1994IV01, 1996TA29: material profiling) and (1995HU15: meteorite analysis).
The angular distributions of ^{6}Li ions corresponding to transitions to ^{12}C*(0, 4.4) have been measured at E_{α} = 27.2 (1995FA21) and 42 MeV (1964ZA1A). At 27.2 MeV, the contributions of the direct and statistical twonucleon transfer processes are estimated by studying the (α, ^{6}Li) reaction on several targets.
Properties of ^{12}C states have been deduced from measurements of the angular distributions of α_{0} and α_{1} particles for E_{p} < 18 MeV [see (1968AJ02)], at E_{p} = 2.99 to 5.14 MeV (1977JA11), E_{p} = 19.85 to 43.35 MeV (1971GU23) and E_{p} = 3.5 to 7.5 MeV (2000IG05). Early results on the angular distributions of alpha particles and 4.4 MeV γradiation indicated that the 4.4 MeV state has J = 2^{+} or > 4 (1953KR1B). The alpha particles to ^{12}C*(4.432 ± 0.010 MeV) were observed along with a transition corresponding to E_{γ} = 4.443 ± 0.020 MeV (1952SC1B). The lifetime of ^{12}C*(4.4) was reported as τ_{m} = 65 ± 9 fsec (1970CO09). At E_{p} = 43.7 MeV the angular distributions to the 0^{+} states ^{12}C*(0, 7.66, 17.76) are fitted by L = 1, while the distributions to ^{12}C*(14.1, 16.1) are consistent with L = 3 [J^{π} = 4^{+} and 2^{+}, respectively] (1972MA21). The energy of the second excited state of ^{12}C is 7654.2 ± 1.6 keV (1973MC01), see additional discussion therein; such a high value leads to a sharply reduced rate for the (ααα) process. At E_{p} = 7.5 MeV, the αγ correlations to ^{12}C*(4.44) were measured and analyzed for θ = 20°160° to deduce spin tensor components and M = 0, 1 and 2 magnetic sublevel populations (2000IG05). The tritoncluster transfer spectroscopic factor amplitudes to ^{12}C*(0, 4.44, 7.65, 14.08, 16.1, 17.76) are deduced from analysis of angular distributions at E_{p} = 9 to 43.7 MeV (2006AB20). This reaction, which decreases proton and ^{15}N abundances in the ^{19}F production sequence, was studied in (1994KA02, 1998AD12, 2003HU10, 2008BA42, 2009LA13, 2011AD03, 2012DE06, 2012IM02); complementary analyses of this reaction using the Trojan Horse Method are found in (2006LA18, 2007LA37, 2008MU07, 2008MU15, 2008PIZZ, 2009LA13, 2010MU16). Parity nonconserving alphadecay reactions are discussed in (1990DU01, 1991DU04, 1991KN03, 2000MI37). Depth profiling and material composition studies using reactions (a) and (b) are discussed in (1990FU06, 1991DU04, 1991IW05, 1992FA04, 1992MA14, 1992MA22, 1994EN07, 1994JA16, 1994OL08, 1996MI28, 1996MI29, 2005KU36, 2010MA26, 2016RE12).
At E_{α} = 42 MeV angular distributions have been obtained for all four of the transitions: ^{12}C_{g.s.} + ^{7}Li*(0, 0.48) and ^{12}C*(4.4) + ^{7}Li*(0, 0.48) (1968MI05). See (1995BO31) for a study of the ^{15}N cluster configurations at E_{α} = 27.3 MeV.
The βdelayed αdecay of ^{16}N can feed only ^{12}C_{g.s.} from ^{16}O*(8.871, 9.585, 9.845) states. In early measurements such as (1959AL06, 1984WA07), a (1.0 ± 0.2)% βdecay branch to ^{16}O*(8.871) was deduced that was based on the beta spectrum following ^{16}N decay; a subsequent reanalysis by the authors resulted in a revised branching ratio (1.06 ± 0.07)% that was detailed in (1986AJ04). However, the small fraction of αdecay from these states yields a significantly lower αparticle intensity. The decay to ^{16}O*(9.585), which αdecays 100% to ^{12}C_{g.s.} dominates the delayed α spectrum; the branching ratio (1.20 ± 0.05) × 10^{5} (1961KA06) has been used extensively in the literature. However the result (1.49 ± 0.05) × 10^{5} (2016RE01) is in poor agreement. A third reported value (1.3 ± 0.3) × 10^{5} (1993ZH13) does little to resolve the discrepancy. In (1961KA06) a gas carrying radioactive ^{16}N passed sequentially through a proportional counter (αcounting) and a GMtube counter (βcounting). The delayed α branching ratio was deduced from analysis that considered lifetimes, flowrates and active volumes. On the other hand, (2016RE01) counted the number of ^{16}N nuclei deposited into a Si detector and the number of subsequent αdecays. At present, we accept the result of (2016RE01), though additional verification of this result would be useful. The smaller decay branches to the neighboring states have been measured relative to the ^{16}O*(9.585) branching ratio, see 12.43 (in PDF or PS). The αdecay of ^{16}O*(8.871) is parity forbidden, and detailed measurements of this decay branch have set limits on irregular parity amplitudes in the wavefunction (1961KA06, 1969HA42, 1970JO25, 1974NE10). In (1974NE10) Γ_{α} = (1.03 ± 0.28) × 10^{10} eV is determined for ^{16}O*(8.87) (1974NE10). It was proposed in, for example, (1971BA99) that the ^{16}N delayed α spectrum gives details on the E1 component of the ^{12}C + α capture cross section in the relevant E_{cm} ≈ 300 keV region. At astrophysical energies the reaction is dominated by the tails of subthreshold states; the interference of these states gives rise to a, so called, "ghost peak" in the delayed αparticle energy spectrum that can be used to deduce the E1 component of the capture reaction. Significant efforts focused on determining the shape of the spectrum (1993BU03, 1993BU18, 1993BU21, 1993ZH06, 1994AZ03, 1997FR12, 1998GA20, 2007FR11, 2007TA34, 2009BU12, 2010TA05).
Reactions (a) and (b) have been studied using Bremstrahling beams with E_{γ} < 42 MeV (1981MA38), < 50 MeV (1997GO16, 2001KI33), < 100 MeV (1981CH28), < 150 MeV (2012AF07), < 300 MeV (1995GO10, 1995KI04), and with polarized quasimonoenergetic beams at E_{γ} = 9 to 11 MeV (2013ZI03). There is evidence for the involvement of many ^{12}C states: see (1965RO05) and references therein. A test of time reversal invariance, via comparison of the ^{12}C(α, γ) vs. the ^{16}O(γ, α) rate found no evidence of Tinvariance (1970VO13). Astrophysical implications of the photobreakup reactions are discussed in (1953HO81). For reaction (c), the dipole and quadrupole decay strengths measured in ^{16}O(e, e'α) reactions to ^{12}C states are discussed in (1990BU27, 1992FR05, 2001DE36, 2008DO15).
These reactions proceed mainly through ^{12}C*(0, 4.4). See references in (1968AJ02, 1975AJ02, 1980AJ01, 1985AJ01, 1990AJ01). ^{12}C*(14.1) is populated at E_{p} = 101.5 MeV (1984CA09). See analysis of the E_{γ} = 4.44 MeV lineshape in (2001KI25). See also (2016OL04).
Angular distributions, mainly to ^{12}C*(0, 4,4), have been measured at E_{d} = 13 to 55 MeV (1975AJ02), E_{d} = 12.7 to 80 MeV (1980AJ01), E_{d} = 50 to 80 MeV (1985AJ01) and E_{d} = 18 to 55 MeV (1990AJ01). Spectroscopic factors are reported in (1984UM04: E_{d} = 54.2 MeV to ^{12}C*(0, 4.4, 7.7, 9.6, 14.1)), (1978BE1T: E_{d} = 50, 65 and 80 MeV to ^{12}C*(0, 4.4, 14.1)), (1978OE02, 1979OE04: E_{d} = 80 MeV to ^{12}C*(0, 4.4, 7.7, 9.6, 14.1, and broad (or unresolved) structures at 14.1 ± 2.6, 19.5 ± 1.5 MeV)), (1980YA02, 1984UM04: E_{d} = 54.25 MeV to ^{12}C*(0, 4.4, 7.7, 9.6, 14.1)).
Reactions involving ^{12}C*(0, 4.4, 9.6) + ^{7}Be*(0, 0.4) and ^{12}C*(7.6) + ^{7}Be_{g.s.} are reported at E(^{3}He) = 25.5 to 30 MeV (1970DE12, 1972PI1A). The αparticle pickup spectroscopic factors are deduced at E(^{3}He) = 26 MeV (1975AU01), 60 MeV (1995MA57) and 70 MeV (1976ST11). See also measurements at E(^{3}He) = 41 MeV (1981LE01).
At E_{α} = 25 MeV reaction (a) proceeds in part by sequential decay via states in ^{16}O and ^{20}Ne (1968PA12). Angular distributions involving ^{12}C*(0, 4.4) at E_{α} = 90 MeV have been analyzed by PWIA and DWBA by (1976SH02): S_{α} = 2.9 ± 0.5 and 0.70 ± 0.23, respectively. In reaction (b), the angular distributions and integrated cross sections of ^{8}Be nuclei (identified through the αdecay) leading to the ground and 4.4 MeV states of ^{12}C have been determined for E_{α} = 35.5 to 41.9 MeV (1965BR13). The α pickup spectroscopic factors have been measured at E_{α} = 55 to 72.5 MeV (1973WO06, 1974WO1D, 1976WO11): S_{α} = 0.25, 1.07, 0.05, 1.40 for ^{12}C*(0, 4.4, 7.7, 14.1) respectively; the excitation of ^{12}C*(9.6) is also reported. See also (1990JA09, 1992JA04, 2008JA02, 2009JA07, 2014JA07).
Reaction (a) was measured at E_{cm} = 7.2 to 10.2 MeV (1988WE17), see analysis in (1994OS08). For reaction (b), see measurements reported in (1974SP06: E(^{16}O) = 24 MeV), (1974RO04: 49 to 64 MeV), (1977PO14, 1979PO14: 68 to 90 MeV), (1979MO14: 65 to 92 MeV), (1983ME13, 1984ME10: 50 to 72 MeV), (1988AU03: 72 MeV), (1996FR09: 51 to 66 MeV) and (1977KA26: E_{cm} = 17 MeV).
At E(^{11}B) = 41.25 MeV the t_{20} and t_{40} polarization tensors of ^{12}C*(2^{+}_{1}) were measured for θ_{cm} = 48°  62° (2000IK02). In addition, analysis of the measured transfer cross sections for reactions leading to ^{12}C_{g.s.} + ^{15}N_{g.s.}, ^{12}C*(4.44) + ^{15}N_{g.s.} and ^{12}C_{g.s.} + ^{15}N*(6.32[J^{π} = 3/2^{}]) appears to indicate significant participation of multistep processes passing through ^{11}B states. See also optical model analysis of measurements at E(^{11}B) = 115 MeV in (1979RA10).
The γrecoil method was used to extract the t_{20} and t_{40} polarization tensors of ^{12}C*(2^{+}_{1}) at E(^{13}C) = 50 MeV for population of ^{12}C*(2^{+}_{1}) + ^{17}O_{g.s.} and ^{12}C*(2^{+}_{1}) + ^{17}O*(870) (2000IK01). An analysis of the spectroscopic amplitudes is also given. See earlier experimental results in (1975SE03, 1976WE21, 1977DU04, 1979BO36, 1979RA10).
The decay of the lowest T = 2 state of ^{16}O to ^{12}C*(0, 4.4) has been studied by (1973KO02).
At E_{d} = 13.6 MeV angular distributions have been obtained for the ^{9}Be groups to ^{12}C*(0, 4.4) (1981GO16). Angular distributions have also been measured at E_{d} = 9 to 14.5 MeV: see (1964DA1B, 1967DE03, 1967DE14).
Angular distributions for the αinduced fission of ^{20}Ne have been measured in the range E_{α} = 13.4 to 20.8 MeV (1981DA13). See also measurements at E_{α} = 12 to 17 MeV (1962LA03, 1962LA05, 1962LA15).
Angular distributions involving ^{12}C_{g.s.} have been studied at E_{p} = 7.9 to 18.6 MeV (1987KI26).
Angular distributions have been reported in (1978SO10: E_{α} = 22 to 26 MeV), (1980BE04, 1980BE15: 90.3 MeV), (1986SK01: 24.9 to 27.76 MeV) and (1989ES06: 26 to 37 MeV).
Angular distributions for reactions that mainly involve ^{40}Ca resonances have been reported in (1978PA04: E = 47 to 57 MeV), (1979LE02: 17 to 31 MeV), (1980PA08, 1980SA12, 1980SA31, 1985SA11: 24 to 54 MeV), (1981NU02: 32 to 48 MeV), (1982FU06: 32 to 36 MeV) and (1989LE19: 46.5 MeV). See also measurements and analyses of the α transfer reaction reported in (1972MA36, 1975ER02, 1976PE05).
