
^{12}C (1968AJ02)(See Energy Level Diagrams for ^{12}C) GENERAL: See also Table 12.7 [Table of Energy Levels] (in PDF or PS). Shell model: (1956KU1A, 1956PE1A, 1957KU58, 1960ME1C, 1960TA1C, 1960WE1C, 1961BA1E, 1961TR1B, 1963NA04, 1963VI1A, 1964AM1D, 1964CL1A, 1964GI1B, 1964GI1C, 1964NE1E, 1965BA2E, 1965CO25, 1965FA1C, 1965NE1C, 1966GI1A, 1966HA18, 1966VA1D, 1966YO1B, 1967CO32, 1967EV1C, 1967KU1N, 1968HI1H). Collective model: (1959BA1F, 1959BR1E, 1961CL10, 1962CL13, 1962GO1R, 1962WA17, 1963GO1Q, 1964BR1H, 1964VO1B, 1965ST22, 1965UB1B, 1965UB1A, 1965VO1A, 1966BO1X, 1966DA1F, 1966DR1F, 1966KR02, 1967BA2N, 1967BO1G, 1967BO04, 1967BR1E, 1967KR1C, 1967LA09, 1967LA1G, 1967PA10, 1967RI1B, 1967RO1G, 1967SA1K, 1967SO1A, 1967SO07, 1967BA1K, 1967BA12, 1967BA2D, 1968MI1E, 1968SO1B). Cluster model: (1956GL1B, 1956PE1A, 1959PI1B, 1960BI1E, 1960IN1B, 1960SH1A, 1966HE1C, 1962MA1H, 1963MA1D, 1963MA1E, 1964GR1M, 1964MA1G, 1965BA2D, 1965BE1H, 1965FA1C, 1965IN1A, 1965KU1E, 1965NE1B, 1965SH11, 1966DA1J, 1966DU1D, 1966HA1R, 1966HE1C, 1966KA1A, 1966BR1U, 1967NO1C, 1967TA1C, 1967UI01, 1968GO01). Special levels: (1959BA1D, 1960BA38, 1960WE1C, 1960ZE1B, 1961YO1A, 1962BA1C, 1963DU1C, 1963SE17, 1964LI1B, 1964NA1G, 1964PA1H, 1966BR2E, 1966ME05, 1966MO08, 1967RO1L). E1 giant resonance: (1960SA1F, 1962NI1D, 1962VI01, 1963MI1B, 1963PE04, 1964GI1C, 1964MI1E, 1966DR1F, 1966LE1J, 1967BA2N, 1967DA1H, 1967DR1D, 1967KE1L, 1967ME1G, 1967MU1F, 1967YO04, 1968KA1M). Special reactions: (1961BE1E, 1961JA1H, 1964AF1A, 1964DU1D, 1964PA1H, 1964RE1B, 1965KR1A, 1965MA1X, 1966DE1G, 1966DU1D, 1966PH1C, 1967AU1B, 1967KA1C, 1967ZI1A). Transition probabilities: (1956EL1C, 1957KU58, 1962KU1D, 1962WA17, 1963BO1D, 1963KI1D, 1963KU03, 1963MA1E, 1964CL1D, 1965GR1H, 1965ST22, 1967HS1A, 1967KU1N). Muon capture: (1965FO1F, 1965UB1A, 1966FR1J, 1967BA78, 1968BA2G). Other topics: (1959CA1B, 1964RA1A, 1966BA42, 1966BO1P, 1966WI1E, 1966YO1C, 1967BL1D, 1967EL1E, 1967NE1G).
Elastic scattering, studied for E(^{6}Li) = 3.2 to 7.0 MeV follows the Mott formula at low energies, but deviates at energies ≳ 4.0 MeV. Angular distributions can be accounted for by the Blair cutoff model, but the parameters are not sharply defined (1966PI02). For E(^{6}Li) = 1.2 to 2.8 MeV, population ratios of ^{7}Be*(0.43), ^{7}Li*(0.48) and ^{10}B*(0.72) remain approximately constant. Simple tunneling or compound nucleus models are not compatible with the data and a direct interaction through longrange tails is suggested (1962MC12). Absolute reaction cross sections at E(^{6}Li) = 2.1 MeV are in reasonable agreement with estimates based on barrier penetration. A strong preference for αemission suggests that the favored mechanism involves interacting clusters (1963HU02). A conspicuous feature of the αspectrum involves a transition through highly excited states of ^{8}Be, possibly those at E_{x} = 22.2 and 22.9 MeV with large ^{6}Li + d parentage (1963KA20, 1964MA26). Angular distributions of α_{0} and α_{1} indicate stripping (1964MA26: 2.0 to 4.4 MeV). Noticeable fluctuations of protons angular distributions and of 0° αyields in the range E(^{6}Li) = 2.4 to 9.0 MeV (1966KI09), and 2.2 to 14.5 MeV (1967AL1F), indicate compound nucleus effects. See also (1962DE1F, 1963BA1Q, 1963CO35, 1963LE19, 1964CA1G, 1964GA1E, 1965NO1A), ^{8}Be and ^{10}B in (1966LA04), and ^{11}B and ^{11}C here.
At E(^{7}Li) = 2.6 MeV, population of the ^{12}C states at 15.11 and 4.44 MeV is reported (1962BE24). See also (1957NO17, 1963KA1E).
See (1963HO1E).
The yield of capture γrays to the ground and 4.4 MeV states (reaction (a)) has been measured for E(^{3}He) = 2 to 4.5 MeV. The cross section increases monotonically; at 4.5 MeV, σ(γ_{0}) is ≈ 4 μb. A strong 17.6 MeV γray is ascribed to reaction (f) (1964BL12). Evidence for decays via higher states of ^{12}C is not conclusive (1963BL05, 1964BL12). Excitation functions for neutrons (reaction (b)) have been determined by (1963DU12: 1.2 to 2.7 MeV; n_{0}, n_{1}, n_{2}, n_{3}, n_{4+5}; θ = 0° and 81.5°), (1965DI06: 1.3 to 4.9 MeV; n_{0}, n_{1}; θ = 0°, 90° and 160°), (1965TO06: 3.5 to 5.8 MeV; n_{0}, n_{1}, n_{2+3}, n_{4+5}, n_{6}, n_{7}, n_{8}; θ = 5° and 90°) and (1968OK1D: 3.5 to 9.9 MeV; n_{0}, n_{1}). See also (1959MA1D, 1962SE1A, 1966MA1R, 1967HA20). No sharp structure is observed but there is some suggestion from angular distribution data and excitation functions at forward angles for a broad structure (Γ ≈ 350 keV) at E(^{3}He) ≈ 2 MeV: E_{x} = 27.8 MeV (1963DU12, 1965DI06). Comparison with (^{3}He, p) shows reasonable similarity at low energies, but strong differences for E(^{3}He) > 2.5 MeV (1965DI06, 1965TO06). For E(^{3}He) = 3.5 to 5.8 MeV the reaction proceeds predominantly by direct interaction (1965TO06). The total cross section for ^{11}C production shows a broad maximum, σ = 113 mb, at E(^{3}He) = 4.3 MeV (1966HA21: 3.2 to 10 MeV). See also (1965BR42, 1967HA20). Angular distributions of the polarization of neutrons to ^{11}C*(0, 2.0, 4.3 + 4.8) have been measured at nine ^{3}He energies from 2.1 to 3.9 MeV by (1967TH1H). See also ^{11}C. Excitation functions and angular distributions for protons (reaction (c)) have been measured for E(^{3}He) = 1.0 to 2 MeV (1967CO03: 90°; p_{2} to p_{9}), 1.8 to 4.9 MeV (1959WO53: total and differential cross sections; p_{0} and p_{1}), 3 to 5 MeV (1959WO53: p_{2} and p_{3}) and 5.7 to 10.2 MeV (1960HI08: 10°, p_{0} to p_{9}; 90°, p_{0}, p_{1}). From E(^{3}He) = 5.7 to 10 MeV the majority of angular distributions are essentially independent of energy, showing pronounced forward peaking, consistent with a predominantly direct process. The excitation curves show only a slow and smooth increase (1960HI08). See also ^{11}B. Excitation functions for groundstate tritons (reaction (e)) for E(^{3}He) = 2.4 to 4.1 MeV (θ = 20°, 40°, 55° and 90°) show a smooth rise with energy in the region explored (1960TA04). At θ = 20° the cross section then shows a broad maximum at E(^{3}He) ≈ 4.5 MeV. Following this maximum, the cross section decreases to E(^{3}He) ≈ 7.5 MeV and then rises slowly to 9 MeV. Angular distributions of groundstate tritons have been measured at 1 MeV intervals between E(^{3}He) = 5.0 and 9.0 MeV (1967EA01). Near E(^{3}He) = 10 MeV, excitation functions for tritons and deuterons show no detailed structure; angular distributions show characteristic direct interaction features. DWBA fits for tritons are less satisfactory than those for deuterons (1967CR04). See also (1960HI08). The elastic scattering excitation function (reaction (g)) has been measured at 45° for E(^{3}He) = 4.0 to 9.0 MeV: it decreases monotonically over this energy region (1967EA01). For reaction (f), see (1964BL12) and ^{8}Be in (1966LA04).
Neutron groups corresponding to ^{12}C levels at 0, 4.4, 7.7, 9.6, (10.1) and (10.8) MeV are reported: see (1960AJ04, 1962NI02). Observation of the γdecay of the 15.1 MeV level is reported by (1954RA35, 1957WA04, 1957WA1F). Angular distributions have been studied by (1959SM98: 1.9 to 2.7 MeV; n_{0}, n_{1}), (1960RE02: 2 to 5.6 MeV; n_{0}, n_{1}, n_{2}), (1960GA14: 3.35 and 5.10 MeV; n_{1}), (1963ME11: 5.3 MeV; n_{1}), (1960AJ04: 5.6 and 5.8 MeV; n_{0}, n_{1}, n_{2}), (1961GA03: 5.5, 5.8 and 6.0 MeV; n_{0}, n_{1}, n_{2}), (1967VE1D: 6 to 10 MeV; n_{0}, n_{1}, n_{2}), (1962KJ02, 1962KJ04, 1962NI02: 9.8 to 14.2 MeV; n_{0}, n_{1}, n_{2}, n_{3+4}), (1962DE1G, 1963DE27, 1965DE1F: 12.9 to 23 MeV; n_{0}, n_{1}) and (1963KO03: 17.5 to 22.1 MeV; n_{0}, n_{1}, n_{3}). Doppler shift measurements on the transition ^{12}C*(4.4 → g.s.) yield a mean life τ_{m} = 50 ± 6 fsec (1961DE38); 57^{+23}_{17} fsec, Γ_{γ} = (11.5^{+5}_{3.2}) meV (1966WA10); ≤ 48 ± 10 fsec (1967CA02): see Table 12.8 (in PDF or PS). 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). Gamma ray angular distributions have been studied by (1955TA28, 1959SM98, 1963SE04). See also ^{13}C. The 7.65 MeV state decays predominantly into ^{8}Be + α (see reactions 15 and 28). The 7.7 MeV nuclear pairs have been observed: Γ_{π}/Γ = (6.6 ± 2.2) × 10^{6} (1959AL97, 1960AJ04, 1960AL04, 1961GA03). See also (1959AJ76) for a survey of the earlier work. See also (1959HE1B, 1959LI1D, 1959NA1B, 1961DE08, 1961EL1A, 1962BR14, 1962EL1C, 1962GO1J, 1962HU1D, 1962ST12, 1963AN1B, 1964SA1J, 1965CL1B, 1967EL1D, 1967VA1J).
Not observed: see (1964CA05).
At E_{d} = 0.95 MeV, the upper limit to the capture cross section is 0.1 μb (1955SA1B).
The thintarget excitation function in the forward direction in the range E_{d} = 0.3 to 4.6 MeV shows some indication of a broad resonance 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). The 0° excitation function for ground state neutrons shows no structure for E_{d} = 3.2 to 9.0 MeV. The angular distributions all show a sharp peak around 20° and a smaller contribution in the background direction. DWBA produces a satisfactory fit to these distributions, but the parameters vary with energy (1967DI01). Crosssection ratios have been obtained at E_{d} = 1 to 5 MeV for the neutrons and protons to the second, third, fourth, and fifth excited states of the ^{11}B and ^{11}C mirror nuclei (1967SC1K). Polarization measurements have been carried out for E_{d} = 2.5 to 4.0 MeV (1967ME1N). See also (1955SA1B) and ^{11}C.
Absolute yields and angular distributions are reported for various proton groups by (1952EN19, 1954BU06, 1954PA28, 1956MA69, 1956VA17, 1959CR1A, 1960CR1A, 1960HA08, 1964BR1A, 1965LE1B, 1967PO01) for E_{d} = 0.14 to 12 MeV. 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 (to ^{11}B*(2.14, 5.03)) (1964BR1A). Studies of plane wave, distorted wave and Coulomb wave Born approximation angular distributions are reported by (1967PO01: see also (1966MO1H, 1967MO1N). There are no significant fluctuations in the yield of protons for E_{d} = 5 to 12 MeV (1965LE1B: θ = 50° and 150°). See also (1965BA31). Yields of gamma rays have been measured by (1955SA1B). Cross section ratios for the (d, n) and (d, p) reactions to mirror states have been measured by (1967SC1K) [see reaction 9]. Polarization measurements have been made by (1959HI1E: 6.9 MeV; p_{0}), (1964BE08: 10 MeV; p_{0}, p_{1}, p_{2} + p_{3}), (1962TA13, 1964PA1E: 11 to 13.8 MeV; p_{0}), (1960TA27: 11.4 MeV; p_{0}), (1963BO1J: 21 MeV; p_{0}). The circular polarization of 2.12 and 4.44 MeV γrays has been investigated at E_{d} = 0.45 MeV (1960ER1A, 1961ZI02, 1962ZI01, 1963ER1A). See also ^{11}B.
See ^{10}B and (1965LE1B, 1967DI01, 1967PO01).
Excitation curves and angular distributions are reported for α_{0} and α_{1} groups (to ^{8}Be*(0, 2.9)) by (1956MA69, 1960BE15, 1961LE10, 1963PU02, 1964AL1Q, 1964BR1A, 1966LO18, 1967LO1J) for E_{d} = 0.4 to 3.3 MeV. Broad maxima are observed in both excitation curves above E_{d} = 1 MeV. Preliminary data at E_{d} = 0.98 MeV indicate the formation of a level in ^{12}C at 26.00 ± 0.01 MeV which decays via ^{8}Be*(2.9) and ^{8}Be_{g.s.} (1967PE1B).
This reaction has been studied for E_{d} = 8 to 13.5 MeV. A DWBA calculation with L = 2 αtransfer gives a qualitative account of the angular distribution (1964GE10).
Not reported.
Proton groups observed by (1958MO99, 1959AL96, 1962BR10, 1967CO1F) are displayed in Table 12.9 (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). The following comments on individual levels derive largely from the ^{10}B(^{3}He, p)^{4}He^{4}He^{4}He studies of (1964ET02, 1965AL1B, 1966WA16): see Table 12.9 (in PDF or PS). ^{12}C*(7.65, 9.6) are observed to decay to ^{8}Be_{g.s.}, confirming natural parity π = (1)^{J} for both states (1966WA16). Pair emission from ^{12}C*(7.66) has been measured: Γ_{π}/Γ = (6.6 ± 2.2) × 10^{6} [see Table 12.8 (in PDF or PS)] as has the cascade through ^{12}C*(4.4): Γ_{γ}/Γ = (3.3 ± 0.9) × 10^{4} (1961AL23). By observation of ^{12}C recoils, a value Γ_{rad}/Γ = (3.5 ± 1.2) × 10^{4} is found by (1964HA23): compare to ^{14}N(d, α)^{12}C. ^{12}C*(10.8) decays to both ^{8}Be*(0, 2.9), indicating natural parity. (1966WA1C) searched for ^{12}C*(10.1) with inconclusive results: see also (1962BR10). ^{12}C*(11.83, 12.71, 13.35) decay to ^{8}Be*(2.9) but not to the g.s., indicating unnatural parity: this result is inconsistant with the assignment (1^{}) to ^{12}C*(11.83): see (1964BR25). For ^{12}C*(12.71) Γ_{γ}/Γ_{α} = (3 ± 1)% (1958MO99), (2 ± 1)% (1959AL96): the cascade through ^{12}C*(4.4) is (20 ± 7)% relative to the groundstate transition (1960AL14): see Table 12.9 (in PDF or PS). The alpha breakup of ^{12}C*(12.71) shows a triplepeaked αparticle spectrum, characteristic of the breakup of a J^{π} = 1^{+} state (1967BH1B). ^{12}C*(14.08) decays both to ^{8}Be*(0, 2.9); the branching ratio Γ(α_{0})/Γ is 0.1  0.4. Proton αcorrelations require J ≥ 2 (1966WA16). ^{12}C*(15.11: J^{π} = 1^{+}; T = 1) decays by γemission to ^{12}C_{g.s.} 97% and to ^{12}C*(4.4) (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): see, however, (1958KA31). ^{12}C*(16.11, 16.57) show decay to 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 [see reaction 19]. For ^{12}C*(16.11) observed 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: (1965DE1R)). The giant resonance excitation region has been searched for levels with a resolution of ≈ 20 keV at E(^{3}He) = 14 MeV. Two peaks have been observed corresponding to ^{12}C* ≈ 20.6 and 24.5 MeV, with Γ ≈ 200 and 50 keV, respectively. Angular distributions show forward maxima. peaks which could be associated with structure seen in photodisintigration experiments are not observed (1967CO1F). See also (1959JO1E, 1961AL10, 1961WO08, 1962KU02, 1965SI05, 1966BA01) and ^{13}N.
At E_{α} = 21.2, 23.0 and 25.0 MeV angular distributions of the deuterons corresponding to ^{12}C*(0, 4.4) have been measured (1967AL16). See also (1959HE1C, 1960ON01, 1965JA03, 1965NI1B) and ^{14}N.
At E(^{6}Li)_{c.m.} = 3.05 MeV, angular distributions have been obtained for α_{0}, α_{1}, α_{2} and α_{3}. The αparticles to ^{12}C*(11.83) and (12.71) have also been observed (1966MC05). At E(^{6}Li) = 3.8 MeV, the population of the T = 15.11 MeV state is about 3 ± 2% of the T = 0 state at 12.71 MeV. It is pointed out that in this reaction the distance of closest approach is 15 fm and the dominant potential would be the Coulomb potential. It is therefore not neccessary to invoke a large T = 0 mixing in the 15.11 MeV state to explain the observation of the 15 MeV γ rays (1964CA18). See also (1963MI02, 1963MO1B, 1965GA1H, 1966BR1G, 1967SE08).
See (1964CA18).
In the range E_{p} = 0 to 25 MeV, twentythree resonances are reported. Their characteristics are displayed in Table 12.10 (in PDF or PS). Cross sections of astrophysical interest are discussed by (1967FO1B). The E_{p} = 0.16 MeV resonance (^{12}C* = 16.11 MeV) is well established as the J^{π} = 2^{+}; T = 1 analogue of the first excited states of ^{12}B and ^{12}N: see (1959AJ76). The resonant energy is 163.1 ± 0.2 keV; Γ_{lab} = 6.5 ± 0.6 keV [see (1955AJ61)]. The gamma decay of the 16.11 MeV state takes place to ^{12}C*(0, 4.4, 9.6): see (1959AJ76, 1961CA13, 1961SE10). The decay to ^{12}C*(9.6) is via a 6.45 ± 0.05 MeV γray whose angular distribution, together with the known αdecay properties of ^{12}C*(9.6), leads to J^{π} = 3^{}. The intensity of the transition is 1% of the γ_{1} decay (1961CA13). See also (1961GR07, 1965CV1A, 1966SO1B). The character of the αdecay at the E_{p} = 0.16 MeV resonance has been studied with coincidence techniques by (1961DE31, 1962DE1H, 1964DE1J, 1965DE1R). Immediately below and above the resonance, a Dalitz plot indicates sequential decay via ^{8}Be*(0, 2.9): in this region, the behavior is ascribed to tails of the E_{p} = 0.675 and 1.4 MeV resonances. At E_{p} = 0.163 MeV, the Dalitz plot shows a striking increase in population near the center, indicative of direct 3α breakup. Some part of the reaction also goes through ^{8}Be_{g.s.}, and there is evidence for a finalstate twobody interaction with l = 2 (1964DE1J): see, however, (1965MA1X, 1965PH1A, 1966CH1L, 1966WA16). See also (1959KA12, 1959KA13, 1960BO26, 1962BE21, 1964DE1H, 1964LO05, 1964LO1E, 1965KR1A, 1965KR1B, 1967KA09, 1967LO1H). Similar studies at E_{p} = 0.675, 1.388 (1965KA1G), 2.0, 2.65, 3.25, 3.73, 4.00, 5.08, and 5.64 MeV (1964PH1A, 1965BR18, 1965PH1A) indicate that sequential decays through ^{8}Be*(0, 2.9) dominate; direct 3α decay is < 5%. The latter work shows evidence for "orderofemission" interference in the shapes of αgroups: see also (1965DU1C, 1965SW1B). See also (1958FO1D, 1966AD1E, 1966SO1B, 1967LO1H, 1968CH1L). The E_{p} = 0.67 MeV state (^{12}C* = 16.58 MeV) has a proton width Γ_{p} ≈ 150 keV. Such a width indicates swave protons and therefore J^{π} = 1^{} or 2^{}. These assignments are supported by the near isotropy of the two resonant exit channels, α_{1} and γ_{1}. The size of the α_{1} cross section indicates 2J + 1 ≥ 5; therefore J^{π} = 2^{}. The reduced width θ^{2}(α_{1}) ≈ 0.05 and the γ_{1} E1 transition has M^{2} ≈ 0.01 Weisskopf units, suggesting T = 1 (1957DE11, 1965SE06). See also (1959AJ76). (1962BL10) report a γbranch to the 12.71 MeV state, ≈ 6% of the intensity of the 4.4 MeV transition. Such a branch may also be present at ^{12}C*(17.23). For the E_{p} = 1.4 MeV state (^{12}C* = 17.23 MeV), (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); see also (1959AJ76). Two solutions for Γ_{p} are possible; the larger (chosen for Table 12.10 (in PDF or PS)) is favored by elastic scattering data (1965SE06). (1963SY01) find no evidence for resonance in α_{0} or α_{1} at this energy. J^{π} = 0^{+}; T = 1 is consistent with all data for the E_{p} = 2.0 MeV resonance (^{12}C* = 17.77 MeV) which decays via the α_{0} and α_{1} channels (1965SE06). The resonance in the yield of α_{0} requires natural parity, and 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 elastic anomaly than is observed (1965SE06: see also (1963SY01)). At E_{p} = 2.62 MeV (E_{x} = 18.36 MeV), the resonance for α_{0} again demands 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^{}; T = 0 is consistent with the resonance data and with the angular distribution of α_{0} at the E_{p} = 1.98 MeV resonance (1965SE06: see also (1955GO10, 1963SY01, 1967FL1F, 1968CH1L)). The E_{p} = 2.66 MeV resonance, distinguished from that at E_{p} = 2.62 MeV by its width, is not seen here: see ^{11}B(p, p). The E_{p} = 3.01 MeV resonance appears only in the angular distributions for α_{0}: the small αwidths suggest T = 1 (1965SE06). At E_{p} = 3.12 MeV (E_{x} = 18.82 MeV), the angular distribution of γ_{0} indicate 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 structure near E_{p} = 3.5  3.7 MeV (E_{x} = 19.2 and 19.4 MeV) 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). 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 (E_{x} = 20.64 MeV); the strength of γ_{1} and absence of γ_{0} favors J^{π} = 3^{}; T = 1 (1963SY01). 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: ∫ σdE = 630 eV · b. σ(γ_{1}) likewise shows a giant resonance centered at about 10.3 MeV (E_{x} = 25.4 MeV), Γ_{cm} ≈ 6.5 MeV, ∫ σdE = 850 eV · b. Both excitation functions show significant fine structure (Table 12.10 (in PDF or PS)): see (1964AL20, 1967FE04). From E_{p} = 4 to 14 MeV the angular distributions of γ_{0} are given by W(θ) = 1 + a_{1}P_{1}(cosθ) + a_{2}P_{2}(cosθ) with the coefficient a_{2} almost constant at 0.6, in approximate agreement with the expectation from particlehole calculations of J^{π} = 1^{}; T = 1 states by (1962VI01). The a_{1} term exhibits fluctuations for E_{p} = 4 to 5.5 MeV in the region of narrow resonances; from 5.5 to 14 MeV it rises smoothly from +0.03 to +0.3. A sharp resonance in σ(γ_{1}) at E_{p} = 10.15 MeV, ∫ σdE = 4 eV · b, may have T = 2 (1964AL20). See also (1959GE33, 1959GO89, 1961GO13, 1963BE18, 1964AL1J, 1964BL1D, 1964TA05, 1965TA1E, 1966HA1M, 1966ME1H, 1966UB01, 1967KA05, 1967KE1K, 1967MA11). For 15 < E_{p} < 25 MeV, a resonance is found at E_{x} = 34.4 ± 0.5 MeV, Γ ≈ 4 MeV, ∫ σ(γ_{0})dE = 38 eV · b (1963RE09: see, however, (1968BR1M)). The resonance is ascribed to a component of the E1 giant resonance, but the cross section is an order of magnitude less than predicted (1963RE09). (1968BR1M) report no pronounced structure for E_{p} = 13 to 22 MeV. See also (1961BL09, 1963FE03, 1963VA1C, 1966AR1D, 1966SU1F, 1967TA1D).
Excitation functions are reported by (1955BA22: E_{p} = 2 to 5 MeV, long counter), (1959GI47: E_{p} = 2.6 to 5.5 MeV, 4π graphite sphere), (1964BA16: E_{p} = 4 to 14 MeV, 4π graphite sphere), (1961LE11: E_{p} = 4.9 to 11.4 MeV, ^{11}C activity), (1965SE06: E_{p} = 3 to 4 MeV, ^{11}C activity), and (1965OV01: E_{p} = 4 to 11.5 MeV: timeofflight resolved groups). The excitation functions are characterized by numerous peaks (see Table 12.11 (in PDF or PS)) whose positions appear to correspond with ^{11}B(p, γ)^{12}C and with some of the (γ, n) and (γ, p) structure, suggesting that resonances, and not fluctuations, are involved. Angular distributions do not change as rapidly as might be expected from the pronounced structure 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 (1959GO89, 1960FU1A, 1961GO13). Polarization measurements have been made for E_{p} = 7 to 11 MeV (1965WA04). See also (1962AL18, 1963VA1C, 1965VA1E, 1966CA1J, 1966SK03, 1967CA1T) and (1959AJ76).
A pronounced anomaly in the elastic scattering is observed near E_{p} = 0.67 MeV at all angles; the level is therefore formed by swaves. The 0.3 to 1.0 MeV results are well accounted for by two resonances: E_{p} = 0.67 MeV, swave, J^{π} = 2^{}, Γ = 0.33 MeV. Γ_{p}/Γ = 0.5, and E_{p} = 1.4 MeV, J^{π} = 1^{} (1957DE11). Higher energy structure in the yields of reactions (a) and (b) are displayed in Table 12.11 (in PDF or PS) (1955BA22, 1963AN12, 1965SE06). See also (1960SA28) and Table 12.10 (in PDF or PS).
See ^{10}B.
Reported neutron groups are listed in Table 12.12 (in PDF or PS). Angular distributions of the neutrons to many of the ^{12}C states up to E_{x} = 17.23 MeV have been reported for energies in the range E_{d} = 0.5 to 10 MeV: see (1957AM48, 1958AM13: 0.5 to 1.15 MeV), (1955WA30: 0.6 MeV), (1955IH1B: 0.69 MeV), (1954GR53: 0.85 MeV), (1957BI78: 0.92 MeV), (1962SA09: 1.0 to 2.0 MeV), (1963KI02: 1.6 to 2.7 MeV), (1961ZD02: 1.1 to 2.8 MeV), (1965SI12: 1.1 to 3.2 MeV), (1965CL02: 1.5 to 4.7 MeV), (1961GA04: 2.7 and 5.4 MeV), (1966HU1H, 1967WI1J: 3.0 to 5.5 MeV), (1965AL17: 2.4 to 9.7 MeV), (1964RO1F, 1966RO1X, 1966WE1B: 6.3 MeV), (1953GI05: 8.1 MeV), (1956MA83: 9 MeV), and (1958ZE01: 10 MeV). See also (1959AJ76) and (1960WA1G, 1961HO1D, 1962LE1A, 1963LA1E, 1964NA02, 1965SI13, 1967DI01). For E_{d} less than 6 to 7 MeV, angular distributions of n_{0} and n_{1} are characterized by both forward and backward peaks, with broad minima near 90°. Detailed shapes are strongly dependent on bombarding energy. The general behavior in the lowerenergy range is ascribed to heavyparticle stripping by (1957OW03, 1958AN32, 1961ZD02), but others (1961GA04, 1965AL17, 1966ST1L, 1967WI1J), find reasonable agreement with DWBA, possibly also with compound nucleus effects (1963KI02, 1965CL02). For E_{d} > 7 MeV, DWBA gives a quite satisfactory account of n_{0} and n_{1} distributions, except for a single example (n_{1} at 8.8 MeV: (1965AL17)). See also (1968YA1G). Angular correlations of neutrons and 4.4 MeV γrays have been studied by (1963HU05: 0.7 and 1 MeV), (1963RI03, 1964RI1D: 1 and 1.2 MeV), (1961ZD02: 1.1 MeV), (1961GA04: 2.65 and 5.35 MeV), (1966RO1X, 1966WE1B: 6.3 MeV). Angular correlations have also been determined for neutrons and 15.1 MeV γrays: see (1963KI14: 2.3 and 2.6 MeV), (1960FE01, 1960FE13: 5 and 8 MeV), (1964RO1F: E_{d} = 6.3 MeV). The formation of the 15.11 MeV state involves l_{p} = 1 with a 12 : 1 ratio between channel spins 2 and 1. The reduced proton width is approximately equal to the singleparticle width (1960FE01, 1960FE13). In the range E_{d} = 1.0 to 5.5 MeV, two slow neutron thresholds are observed at 1.627 ± 0.004 MeV (E_{x} = 15.109 ± 0.005 MeV) and near 4.1 MeV (broad; E_{x} = 17.2 MeV) (1955MA76). At the lower threshold, 15.1 MeV γrays are observed: E_{d} = 1.633 ± 0.003 MeV, width less than 2 keV (1958KA31) [E_{x} = 15.110 ± 0.003 MeV]. A study of the angular distributions and energy spectra of αparticles from the decay of ^{12}C states shows that the 12.71 and 11.83 MeV states decay sequentially via ^{8}Be; the former via ^{8}Be*(2.9), the latter 90% via ^{8}Be*(2.9) and 10% via ^{8}Be(0). There is some evidence that the 10.84 MeV state decays primarily to ^{8}Be(0). J^{π} = 3^{} for the 9.64 MeV state is favored on the basis of the angular distribution of the αparticles to ^{8}Be(0). There is no evidence for direct 3α decay 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). See also ^{13}C, (1959AJ76) and (1958ED1B, 1962KU02, 1962NA04, 1962RO1L, 1963RO1K, 1965MA1K, 1966ST1L).
Observed deuteron groups are displayed in Table 12.13 (in PDF or PS) (1960FO01, 1961HI08). Excitation functions near 10 MeV show no structure; angular distributions exhibit characteristic direct interaction features (1967CR04). See also (1959HO01, 1959WO1B, 1961HO1F) and (1967AD1F).
Differential cross sections have been obtained for the groundstate tritons and for the tritons to ^{12}C*(4.4), in the forward direction at E_{α} = 43 MeV: singleproton transfer seems to be the dominant reaction mode (1967DE1K). The angular distributions appear to be affected by final state spin (1967SI1A).
See (1962NE01).
The decay is mainly to the ground state of ^{12}C; branching ratios to other states are listed in Table 12.14 (in PDF or PS). The halflife is 20.41 ± 0.06 msec (Table 12.2 (in PDF or PS)). Since transitions to ^{12}C(0^{+}) and (2^{+}) are allowed, J^{π} of ^{12}B is 1^{+}. Since the decays of ^{12}B and ^{12}N are mirror transitions, comparison of the ft values has some interest. According to (1964KA08), ft(^{12}B) = 11.800 ± 70 sec, ft(^{12}N) = 13.060 ± 90 sec; the ratio ^{12}N/^{12}B is 1.11 ± 0.01: see also (1963FI05, 1963PE10, 1964FI02, 1964NA1C, 1964WU01, 1966BA1A). Possible explanations of the difference are discussed by (1963HU10, 1964EI1C, 1965BL1F, 1966MA2R, 1966OK1B). Comparison of shape factors for the groundstate βtransitions for ^{12}B  ^{12}N provides a test of the conserved vector current theory. The correction to the simple Fermi shape should have the form 1 + AE for ^{12}B and 1  AE for ^{12}N where A is determined mainly by the (experimental) M1 width of the ^{12}C*(15.1) T = 1 level: A(theor.) = 0.52 ± 0.12% MeV^{1} (1958GE1C, 1959GE1D, 1963KI1D, 1964WU01): see also (1959FL41, 1959MO27, 1960WE1C, 1961MO1C, 1967HU10). The experimental values of (1964WU01) are A = 0.55 ± 0.10 and 0.52 ± 0.06 for ^{12}B and ^{12}N, respectively: see also (1961MA16, 1962LI05, 1962MA22, 1962MC14, 1963GL04, 1963LE05, 1965WU1A). Transitions to ^{12}C*(4.4), J^{π} = 2^{+}, are allowed. According to (1963PE10) the ratio ft(^{12}N)/ft(^{12}B) = 0.92 ± 0.06. The level energy is 4438.91 ± 0.31 keV (1967CH19). The level at E_{x} = 7.6 MeV has special interest for helium burning processes in stars (1963SE17, 1963SE23, 1967FO1B). Observation of the αspectrum yields Q(^{12}C*  ^{8}Be  ^{4}He) = 278 ± 4 keV (1957CO59). With Q(^{8}Be  2^{4}He) = 92.12 ± 0.05 keV (1966BE05), Q(^{12}C*  3^{4}He) = 370 ± 4 keV. Using (1965MA54) masses for ^{8}Be and ^{4}He, ^{12}C* = 7647.0 ± 4.1 keV. Although the level decays mainly by αemission, both the gamma branch to ^{12}C*(4.4) and pair emission to ^{12}C_{g.s.} have been observed in various reactions. The relevant parameters are given in Table 12.8 (in PDF or PS) (see (1963AL15, 1963SE23)). The fact that the βdecay is allowed indicates J^{π} = 0^{+}, 1^{+} or 2^{+} for ^{12}C*(7.6); observation of the α particles eliminates J^{π} = 1^{+}, and the large Γ_{α} requires J^{π} = 0^{+} (1957CO59). The 10.3 MeV level is observed in both ^{12}B and ^{12}N decays. The excitation energy given by (1966SC23) is 10.3 ± 0.3 MeV, Γ = 3.0 ± 0.7 MeV. The decay is to ^{8}Be_{g.s.}. With R = 5.2 fm, θ^{2}_{α} = 1.5 and 7.5 for J^{π} = 0^{+} and 2^{+}, respectively (1958CO66). It is suggested by (1966MO08) that this level is a highly deformed rotational state with J^{π} = 2^{+}, related to ^{12}C*(7.66). Some fraction of the observed αspectrum is presumed to result from a "ghost" of the lower level (1962BA1C, 1963WI05, 1964BL12). In ^{12}N, allowed transitions are observed to ^{12}C*(12.7) and (15.1) (AL66J, 1966SC23: see also (1963GL04, 1963WI05)). The 12.7 MeV level decays primarily to ^{8}Be*(2.9; J^{π} = 2^{+}); the absence of decay to ^{8}Be_{g.s.} is in agreement with the assignment J^{π} = 1^{+} (1966SC23). The ft values for both βtransitions (see Table 12.25 (in PDF or PS)) agree well with shell model calculations of (1965CO25). In particular, the agreement strongly suggests a close relation between ^{12}C*(12.71; J^{π} = 1^{+}; T = 0) and ^{12}C*(15.11; J^{π} = 1^{+}; T = 1). A search for the transition from ^{12}B to ^{12}C*(12.71) was unsuccessful (1967AL03). See also (1959JA1B, 1960FA02, 1964SH1J, 1966DU1E).
The lifetime of the 4.4 MeV state has been determined by resonance scattering and absorption as τ_{m} = 65 ± 12 fsec (1958RA14). See Table 12.8 (in PDF or PS). Resonance scattering and absorption by the 15.1 MeV level have been studied by (1957HA13, 1959GA09, 1960BU14, 1960HA1H, 1961BU1E, 1963SC21, 1967KU11): partial widths are displayed in Table 12.15 (in PDF or PS). The scattering angular distribution is W(θ) = 1 + cos^{2}θ, indicating dipole radiation (1959GA09); the azimuthal distribution of scattered polarized radiation indicates M1 (1960JA01) and the large Γ(M1) indicates T = 1. The groundstate γwidth of ^{12}C*(16.11) is reported as Γ_{γ} = 7.5 ± 1.9 eV (1959KE19: see, however, (1961SE10)). For ^{12}C*(17.22), the scattering cross section is 1.0 ± 1.0 μb, consistent with Γ_{γ} given by ^{11}B(p, γ) (1963SC21). See also (1960WE1C). At higher energies, elastic scattering studies show the giant resonance peak at ≈ 24 MeV (see ^{12}C(γ, n)^{11}C), dσ/dΩ(135°) = 4 μb/sr. A considerable tail is visible, extending to > 40 MeV (1959PE32). See also (1958WO53, 1961DE22, 1961WI1G, 1962SE02, 1967LO1B).
Recent review papers dealing with this reaction are: (1963HA1E, 1965DA1D, 1965SH1G, 1966BA2Y, 1966FU1C, 1966ME1H). The total absorption, mainly (γ, p) + (γ, n), in the range E_{γ} = 13 to 30 MeV is dominated by the giant resonance peak at 23.2 MeV, Γ = 3.2 MeV [E_{x} = 22.6 MeV from ^{11}B(p, γ)^{12}C]. This single peak accounts for 64% of the total strength below 27 MeV. The total integrated cross section to 35 MeV is 144 MeV · mb, about 80% of the classical sum rule, 60 NZ/A MeV · mb: see Table 12.16 (in PDF or PS). Other resonant structure is reported at E_{γ} = (16.5), 17.5, (19.1), 26 and 29 MeV: see Table 12.17 (in PDF or PS) (1960ZI01, 1963BU1G, 1965WY02). See also (1958MO1F, 1958WO53, 1958ZI1B, 1959BU1H, 1959KO55, 1959KU84, 1959PE21, 1960CA09, 1960TA15, 1960WY1A, 1962DE03, 1962MI07, 1963BU18, 1963CO1D, 1965MA1N, 1967BR1P, 1967DR1E). Shellmodel calculations on the structure of the giant resonance ascribe the main effect to four J^{π} = 1^{}; T = 1 levels formed from the particlehole configurations p^{1}_{3/2}s_{1/2}, p^{1}_{3/2}d_{5/2}, p^{1}_{3/2}d_{3/2} and s^{1}_{1/2}p_{1/2}, of which the second contributes most of the E1 strength. The computed energies are 19.6, 23.3, 25.0 and 35.8 MeV [the most probable identifications are E_{x} = 19.2, 22.6, 25.4 and 34.4 MeV (Table 12.7 (in PDF or PS))] ((1964LE1D), and references therein). Calculations with a deformed potential suggest a somewhat more complicated structure (1962NI1D). See also (1961BA1D, 1962VI01, 1963BO21, 1963MI1B, 1964GI1C, 1964MI1E, 1965DA1D, 1966FU02, 1966LO04, 1966UB01, 1967LE1H, 1967MA1P). Observations of σ(γ, n) show a giant resonance centered at about 22.5 MeV, σ(peak) ≈ 8 mb, Γ ≈ 3 MeV, with a long tail slopping off to about 40 MeV. The integrated cross section to 40 MeV is about 60 MeV · mb; integrated to 250 MeV, it is about 80 MeV · mb (Table 12.16 (in PDF or PS)). In the giant resonance region, the angular distribution of groundstate neutrons is W(θ) = 1 + 1.5sin^{2}θ, consistent with l_{n} = 2 ejection (1960EM02, 1964AL33, 1965VE03: see, however, (1967HA1P)). For E_{γ} = 28 to 145 MeV, comparison with (e, e'n) indicates mainly E1 processes, with ≲ 8% E2 (1958BA60: see also (1961RO1H)). The giant resonance appears to have a fine structure (Table 12.18 (in PDF or PS)): at least two major components are identified at E_{x} = 22.0 and 23.5 MeV (1966FU02, 1966LO04: see also (1966CO09, 1967FI1E)). A satellite at E_{x} = 25.5 MeV is also well established: a large fraction of the decay of this level (6 MeV · mb) involves excited states of ^{11}B and ^{11}C (1966MA1T: see also (1966CO09, 1966FU02)). Up to 28 MeV, about 83% of the neutrons leave ^{11}C in the ground state (1966FU02). Several broad levels are indicated in the range E_{x} = 27 to 35 MeV (1966CO09, 1966FI1D, 1966FU02, 1967FI1E). A possible level near 52 MeV is reported by (1966FO06). See also (1962BO1H, 1966BI1B, 1966CO09). Considerable fine structure in the range E_{x} = 19 to 23 MeV is reported by (1959SA06, 1960GE06, 1961TH03, 1966CO09): see also (1959CO62, 1959VA1D, 1960EM02, 1962FU11, 1965MI03). Polarization of neutrons has been studied by (1964BE1E, 1964HA1F, 1966RA1E, 1967HA1N, 1967HA1P). See also (1959OC07, 1961BR28, 1961PR07, 1961RO1C, 1962MI07, 1963FU05, 1965BI1G, 1966KA1C, 1966ME1H, 1967AN11, 1967AU1F, 1967FE05, 1967GL1B, 1967SM1A).
The photoproton cross section exhibits a single broad giant resonance peak centering at E_{γ} = 22.5 MeV, (Table 12.19 (in PDF or PS)). There appears to be a significant difference from σ( γ, n) both in shape and peak cross section (1963HA1E, 1966FU1C, 1966ME1H): such a difference could result from a comparatively small isospin mixing (1957BA1K). Some fine structure is suggested by the work of (1956CO59, 1962DO1A, 1963MU08, 1963WA18, 1964SH24, 1964TA1G): compare ^{11}B(p, γ)^{12}C. The angular distributions near the giant resonance are consistent with W(θ) = 1 + 1.5sin^{2}θ expected on the IPM (1962DO1A). For higher energies, an appreciable cosθ term makes its appearance (1959PE22, 1961VA10, 1963WA18). See also (1965DA1D, 1967FR1E). The azimuthal distribution observed with polarized γrays at E_{γ} = 21.3  21.6 MeV is not inconsistent with E1 (1966KE06). Evidence for involvement of excited states of ^{11}B for E_{γ} > 30 MeV is reported by (1959PE22). See also (1960BA1P, 1963BU1G, 1963FI1B, 1966MA1T, 1966RA1E, 1967LE1H). At high energies, E_{γ} ≳ 150 MeV, the cross section for photoproton production remains relatively large (≈ 100 μb) and the angular distributions show forward peaking. The high internal momenta thus implies may be understood on a quasideuteron picture, in which the interaction involves neutronproton pairs in close proximity within the target nucleus (1951LE1B). This picture is strongly supported by the observation that most, if not all, high energy photoprotons are accompanied by neutrons with the proper kinematical relation (1954MY1A, 1958BA1C, 1958WH35); see, however, (1965RE1B). Experimentally derived momentum distributions are reported by (1961CE1B, 1963KI03, 1963KI1C). See also (1958MA1A, 1959CH25, 1961MA36, 1961SH1C, 1962CH26, 1962PA08, 1964JI1A). Polarization of the photoprotons has been studied by (1962LI13). See also (1959PE21, 1962FE12, 1963BO21, 1963FU1D, 1964MO02, 1964SE09, 1966RA1G, 1967MA1P), ^{11}B(p, γ)^{12}C and ^{12}C(e, ep)^{11}B.
For E_{brems} = 90 MeV, the ratio of yields of deuterons to protons is ≈ 2%, for particle energies 15 to 30 MeV. For higher particle energies, the ratio decreases. Angular distributions are similar for (γ, d) and (γ, p), with strong forward peaking. These observations are consistent either with a quasideuteron mechanism or with a twostage pickup process (1962CH26: see (1962MA1F, 1964SH1B)). According to (1964SH1B) the high apparent threshold for ( γ, d) reflects the presence of continuum states of ^{10}B with a high parentage in ^{12}C. See also (1959CH25, 1960SH1D, 1963BA1K, 1964KI1D, 1965KI04, 1967SM1A).
See (1968BU1D).
The cross section exhibits broad peaks at about 18 MeV and ≈ 29 MeV; a pronounced minimum occurs at 20.5 MeV: to what extent the peaks have fine structure is not clear (1953GO13, 1955CA19, 1955GO59, 1955JO1C, 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). Integrated cross sections are 0.82 ± 0.03 MeV · mb (1964TO1A: to 20.5 MeV), 1.21 ± 0.16 MeV · mb (1953GO13: to 20.5 MeV), 2.8 ± 0.4 MeV · mb (1953GO13: 20.5 to 42 MeV) and < 0.2 MeV · mb (1953GO13: 42 to 60 MeV). Alpha energy distributions show surprisingly strong E1 contributions below E_{γ} ≈ 17 MeV (1955GO59, 1964TO1A). See also (1958MA1A, 1960GA16, 1961SE13, 1964WA1J, 1965RO1J), and (1959YO1B, 1964LE1C, 1965DZ1A, 1965DZ1B).
Reported integrated cross sections for reaction (a) are for 25 to 40 MeV: 1.61 MeV · mb (1962MO16), 1.35 MeV · mb (1956LI05), 3.85 MeV · mb (1958MA1A); for 25 to 120 MeV: 1.9 ± 0.4 MeV · mb (1962MO16). For production of ^{7}Be (reaction (b)), the integrated cross section to 57 MeV is 6.0 ± 0.4 MeV · mb (1966AR01).
Elastic scattering has been studied up to 800 MeV: momentum transfers q^{2} ≤ 11.5 fm^{2} (1959ME24, 1964CR11, 1966CR07). The form factor is well accounted for by a harmonicwell model with R(r.m.s.) = 2.40 ± 0.02 fm. Only one diffraction minimum is observed (1966CR07). R = 2.42 ± 0.04 fm (1967EN1C), R = 2.58 fm (1967EL1B), R = 2.35 ± 0.1 fm (1966AF1A: see also (1967AF02, 1967AF04, 1968AF1A)). See also (1960IN1A, 1963GO04, 1965MU1B, 1965RA1F, 1967BE1P, 1967BO1X, 1967EL1B, 1967FR1D, 1968BR1N). Sharp inelastic peaks are reported corresponding to ^{12}C*(4.4, 7.7, 9.6, 15.1 and 16.1 MeV) (1956FR27, 1956HE83, 1959BA36, 1959EH1A, 1960BA47, 1961BO32, 1961DU09, 1962ED02, 1963BO36, 1963GO1P, 1964BR1N, 1964CR11, 1964GO14, 1965GU04, 1966CR07, 1967AR1A, 1967CR01, 1967PE07). Observed widths are reported in Table 12.20 (in PDF or PS). Additional structure in the range E_{x} = 16.6 to 25.5 MeV is reported by (1963BO36, 1966PR1C). The variation of the form factor F(q^{2}) with momentum transfer yields unambiguous assignments of J^{π} = 2^{+}, 0^{+} and 3^{} for the first three levels (1960BA38, 1964CR11, 1967HA1U). There is some evidence of a diffraction structure in F(^{12}C*(4,4)) at high momentum transfer (1966CR07). Transverse and longitudinal scattering form factors from ^{12}C*(4,4) have been measured by (1967BE43). The 15.1 MeV transition is a strong M1: J^{π} = 1^{+}; T = 1: the indicated Γ_{γ} is somewhat lower than the mean from ^{12}C(γ, γ) (1964GO15, 1964GU05, 1965FO1F). The theoretical value is sensitive to the spinorbit coupling parameter, but a pure p^{4}_{3/2} ground state seems to be excluded (1964BI1H, 1964KU1G). The 16.1 MeV level corresponds to that observed in ^{11}B(p, γ)^{12}C. Γ_{γ0} = 0.184 ± 0.045 eV is obtained from the electron data, and T = 1 is confirmed (1961DU09, 1964BI1H, 1965BI1B, 1966PR1C). See also (1960IN1A, 1962KU1C, 1963BO36, 1964GI1A, 1965IN1A, 1965SE1D, 1967SH1L). Inelastic excitation of the giant resonance has been studied by (1959BA36, 1960BA47, 1961BO32, 1963BO36, 1963GO1P, 1963LE1H, 1964GO14, 1966PR1C). There appears to be evidence for structure at 18.1 ± 0.05, 19.5 ± 0.05 (Γ = 0.5 ± 0.1), ≈ 24 and ≈ 34 MeV (1964GO14: see also (1967CR02)). The variation of F(q^{2}) with q^{2} in the range 0  0.6 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)). See also (1960FA1E, 1965LE1D, 1966FR1H, 1966UB01, 1967BI1K). Reported integrated cross sections are 75 MeV · mb (1960BA47), 50 MeV · mb (1963GO1P). See also ^{12}C(γ, n)^{11}C. 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, 1966BE1Q, 1967BI1K, 1967CR02, 1967DR1C). A positive parity state with a large longitudinal matrix element may also be present (1967BI1K). See (1962BA1D, 1964BA1R, 1966DE1K, 1966GO1C, 1967WA1E, 1967WA1F) for general discussions. See also (1960DE1A, 1963PO1B, 1964ZI1A, 1966BO1N, 1966BO1P, 1966GI1A, 1966KA1C, 1966PE1E, 1966SI1E, 1967CZ1B, 1967IS1A).
Electron spectra in the region of large energy loss show a broad peak which is ascribed to quasielastic processes involving ejection of single nucleons from bound shells: see (1961BO32, 1963CZ1A, 1966DE1K). A study of e'  p coincidences for incident energies around 550  600 MeV reveals peaks corresponding to ejection of 1p and 1s protons: the results are consistent with observations in (p, 2p) (1961JA1L, 1964AM1C, 1967AM1E). Angular distributions for the two groups are analyzed by (1967AM03) in terms of proton momenta. See also ^{12}C(γ, n)^{11}C, ^{12}C(γ, p)^{11}B and (1961GO1R, 1961RO1H, 1961VA10, 1962DO1A, 1962PA08, 1963BO36, 1964SU1B, 1966RA1C, 1967DE1P, 1968AM1A).
Elastic and inelastic scattering have been studied at many energies up to 350 MeV. The data are summarized by (1963GO1M, 1964ST25); some later references are listed in Table 12.21 (in PDF or PS). At E_{n} = 14 MeV, the elastic angular distribution shows a forwardpeaked diffraction structure indicating direct interaction. Optical model fits in the forward hemisphere are satisfactory but fail at back angles (1963LU10, 1964CL05). A strongcoupling calculation has been made by (1965BL09). polarization studies at E_{n} = 24 MeV are in fair agreement with optical model predictions and yield a sign for the spinorbit coupling in agreement with shell model predictions (1962WO08: see also (1960SA1E, 1965BR1E)). See also (1959GL57, 1959KE1A, 1959WI1C, 1960HO14, 1960RO24, 1964CR1B). At 14 MeV the cross sections for n_{0}, n_{1} (4.4) and n_{2} (9.6) are about 800, 220 and 100 mb, respectively: see (1963BO15, 1964ST25, 1966GR1L, 1967GR1P). Angular distributions at E_{n} = 14 MeV of neutrons corresponding to ^{12}C*(4.4) show direct interaction, but DWBA optical model fits are unsatisfactory (1964CL05: see also (1959GL57, 1960PE02, 1960RO24)). (1967GR1P) find that coupled channel calculations, with ^{12}C*(0, 4.44, 9.64, 10.84) taken as collective states yield fair agreement with the experimental angular distributions at E_{n} = 14 MeV. See also (1962BA15, 1962BA25, 1962CO1E, 1963HO08, 1964JO1E). The angular correlation (n', γ_{4.4}) has forward neutron angles the distributions are similar to (p, p'γ) while a strong difference is apparent at θ_{n} = 135° (1963BE31, 1966BE1R). See also (1961AS1B, 1963MO04, 1964MO1D, 1965LA1D). See also (1958AN32, 1958NA09, 1959GA1D, 1959HA06, 1959SI79, 1960DE10, 1960HE10, 1960PE1A, 1961BR08, 1961JA19, 1961ST22, BL62C, 1962BO06, 1962BR11, 1962ST18, 1962TE05, 1963ED1B, 1963GA1G, 1963KO1C, 1963MC1B, 1963OP1A, 1963SE1P, 1964AD1B, 1964EN1B, 1964OL1B, 1964PE20, 1966BR1D, 1966CI1A, 1966FE1C, 1966JO1B, 1966KA1E, 1966KO1D, 1966LI1F, 1966MO1C, 1967BR23, 1967CH1R, 1967LE1G) and ^{13}C. At E_{n} = 14.2 MeV, reaction (c) proceeds about 50% through ^{12}C states which then decay via ^{8}Be_{g.s.} and ^{8}Be*(2.9). Most of the remainder of the observed events take place through ^{12}C(n, α)^{9}Be* → n + ^{8}Be* and ^{12}C(n, α)^{9}Be* (α) ^{5}He* (n) α. The reaction ^{12}C(n, ^{5}He*)^{8}Be* cannot be excluded. Fourbody breakup is not necessary to explain the results. 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: see also (1966MO05)). See also (1959TS1A, 1960VA10, 1962BA15, 1962BA25, 1964SA1E, 1965GR1V, 1965GR1W, 1966CI1A, 1966FE1C, 1966GR1M).
Up to E_{p} ≈ 12 MeV, the elastic scattering exhibits resonance structure: see ^{13}N. References to elastic and inelastic studies at higher energies are listed in Table 12.22 (in PDF or PS). Excitation functions for both (p, p) and (p, p_{1}(4.43)) exhibit pronounced resonancelike structure for E_{p} = 14 to 20 MeV (1957PE14, 1961NA02, 1964DA03). An optical model analysis gives a good account of the data, but the parameters vary strongly with energy (1962NO03: see also (1962RO14)). Between 18 and 30 MeV the elastic scattering and polarization angular distributions show strong energy dependence, while those for inelastic groups are much smoother (1963DI04, 1963DI16, 1966CR04). An optical model analysis with resonances is discussed by (1964TA1E); see also (1965BA1M). At 40 MeV an 11parameter optical model fit is satisfactory for elastic differential cross sections, but unsatisfactory for polarization data (1966BL19, 1967FR20: see also (1965BA54, 1965FR17)). The same problem arises with the data at 46 MeV (1967SA13) and 49 MeV (1966CR14). For analysis of the 140 MeV small angle results, see (1966JA08). See also (1958BE1B, 1959WI1C, 1962RO1F, 1964CR1B, 1967BE1Q, 1967TA1B). At 1 MeV, the differential elastic scattering cross section exhibits diffractionlike structure associated with the multiple scattering of protons by nucleons inside the nucleus (1967PA25). At E_{p} = 40 MeV, angular distributions of inelastic protons corresponding to ^{12}C*(4.4, 7.7, 9.6) confirm the assigned parities even, even, odd, respectively. Comparison of deformation parameters for ^{12}C*(4.4) determined by (p, p'), (α, α') and (e, e') show considerable differences (1964ST15): see, however, (1966BA2K, 1967SA13). Angular distribution measurements at E_{p} = 46 MeV (1967PE05) have been analyzed by (1967SA13): a large quadrupole deformation was found (β_{2} ≈ 0.6); the inelastic scattering agrees best with deformation of both the real and imaginary parts of the optical potential; the angular distribution for ^{12}C*(7.6) is best described by double quadrupole excitation via ^{12}C*(4.4). ^{12}C*(14) is interpreted as the 4^{+} rotational state. The similarities of distributions corresponding to ^{12}C*(10.8, 11.8) suggest that they have the same spin (1967SA13). Asymmetries observed with 40 MeV polarized protons on ^{12}C*(4.4) disagree with DWBA predictions (1966FR1G: see also (1967SA13)). See also (1960BA38, 1963DI16, 1964DA03, 1965FR17, 1966BL19, 1967FA06, 1967LE13, 1967LE1G, 1967PA1L, 1967SA1L, 1968GA1H, 1968TA1P). A number of inelastic groups have been studied at E_{p} = 155 to 185 MeV: see Table 12.23 (in PDF or PS). When treated in the impulse approximation, the cross sections and angular distributions are closely related to the electric transition moments. Comparison of (p, p') and (e, e') form factors yield the transition multipolarities indicated in Table 12.23 (in PDF or PS) (1964JA03: see also (1960NI02, 1961BR08, 1961PI04, 1962BR11, 1962RO1F, 1962SA1G, 1963HO1D, 1963NI02, 1964HA1L, 1965HA17, 1965HA28, 1966HA51, 1967HA1U, 1967JO1F). The broad levels reported in the range E_{x} = 20 to 24 MeV are associated with the giant E1 resonance (1961SA1E, 1962SA1G, 1963DE35, 1965HA17). The energy of the first excited state is 4440.0 ± 0.5 keV, from the γray. The character of the Doppler broadening indicates rather little spinflip contribution to the inelastic scattering (1967KO14: E_{p} = 23 MeV). Proton γangular correlations provide a sensitive measure of the spinflip: for E_{p} = 10 to 15 MeV a considerable contribution is observed (1964SC07, 1966SC1L: see also (1961AD04, 1961CL1D, 1961GI1C, 1961GO13, 1962NO04, 1964BA14, 1964RO23, 1967GI1D, 1967KO1N) and Table 12.21 (in PDF or PS)). The following is a list of other recent theoretical and review papers dealing with this reaction: (1959GL57, 1959HO95, 1959MC63, 1959PU1A, 1960BE31, 1960LU1B, 1960MA43, 1960MI1C, 1960SA1C, 1960SA1E, 1960SA1G, 1961DO1C, 1961GI1D, 1961MC1C, 1961SA1B, 1962KA1E, 1962MA1P, 1962NI1C, 1963BU1E, 1963LO1A, 1963VI1A, 1964DA07, 1964HO1C, 1964SA1L, 1965CL1E, 1966BO1P, 1966GI1A, 1966LI1F, 1966SA1D, 1967CH1R, 1967VA1K) and (1959AJ76). See also (1960WA15, 1961CL09, 1961RA1B, 1964SC1F, 1965DE14, 1965JA1A, 1966YA04). Reaction (b) is widely used to monitor highenergy proton beams: see (1963CU05, 1963CU1B). For studies of recoil spectra, see (1962SI09, 1965BE1U). Possible emission of singlet deuterons is discussed by (1966NO1A). See also (1967HO1M). In the summed proton spectrum of reaction (c), peaks are observed corresponding to the ejection of p and sshell protons: see ^{11}B. Absolute cross sections are reported by (1965GI1F). See also (1962AU1A, 1962ST1F, 1964LI1D, 1964LI1E, 1965MC1F, 1965RI1A, 1966BE1B, 1966KO1F, 1966JA1A, 1967CO1V, 1967EL1C, 1967GO01, 1967JA1C, 1967RI08, 1968JA1G, 1968YU1B). At E_{p} = 57 MeV the reaction involves an excited state at 20.3 MeV (1967EP1B, 1968RO1L). For reaction (d) see (1963SH1A, 1965BA11, 1967SU1C, FR68A). See also (1962AU1A, 1964BA1P). Reaction (e) has been studied up to E_{p} = 660 MeV. Various states in ^{12}C appear to be involved. At E_{p} = 57 MeV, the sequential process dominates; αdecay to ^{8}Be_{g.s.} is observed via ^{12}C*(21.1, 22.2, 26); comparison with other reactions suggests (J^{π}; T) = (1^{+}, 3^{+}; 0), (1^{}; 0 + 1); (π = natural; significant T = 0 component) (1967EP1B). See also (1966RO1D, 1968RO1L). See also (1959VA15, 1960VA10, 1961VA17, 1962VA1A, 1962ZH1B, 1963JA07, 1963VA04, 1963ZH1A, 1964BA29, 1964KE1F, 1964SY02, 1964YU1A, 1965IS05, 1965KU14, 1965SA1K, 1965YU1C, 1965ZH1A, 1966JA1B, 1966ZE1A, 1967GA01) and (1959AJ76). Total proton reaction cross sections are reported by (1959BU97, 1959GO90, 1964GI05, 1964GR1M, 1967CA1K).
The angular distribution of elastically scattered deuterons has been studied at a number of energies from E_{d} = 2.8 to 650 MeV: see (1954FR24, 1960BU25, 1960CA24, 1961IG02, 1961IS02, 1961LO01, 1962SL02, 1963BU24, 1963CA1E, 1963FR1F, 1963VA23, 1965DI1C, 1965DU01, 1966CO24, 1966DO1B, 1966DU08, 1966GA09, 1966GE03, 1966NG01, 1967AU05, 1967DU1E, 1967FI07, 1967NE09, 1967PL1B, 1967WA1M). Inelastic groups corresponding to levels at 4.4 and 9.6MeV are reported by (1961JA02, 1962SL02, 1966NG01: see also (1951KE02, 1954FR24, 1956GR37, 1956HA90)). The angular distributions of inelastically scattered deuterons to these two states and to ^{12}C*(7.7) have been measured at E_{d} = 25.9 MeV (1963VA23). A systematic optical model analysis yields a set of smoothly varying parameters which give a good account of the elastic angular distributions from E_{d} = 3 to 34 MeV. For the inelastic scattering, Q = 4.4, deformation of the potential corresponding to β = 0.4  0.6 was required (1966SA1C). See also (1961CI08, GO61I, 1963CA1J, 1963SA1G, 1968HI1H), (1958MA52, 1960EL09, 1960FA05, 1960LU1B, 1961RO1G, 1962SA1J, 1963ST1A, 1963ZA1B, 1964HE1H, 1964HO1C, 1964RU1A, 1964SA1K, 1965CA1F, 1965TJ1A, 1966BA2W, 1966JA1J, 1966MA2Q, 1967RE1E, 1967RU1A; theor.) and (1959AJ76). For reaction (b), see (1963PH1A, 1965LA08, 1965LA1F, 1967MA1N, 1967NO1A) and ^{13}N.
Differential cross sections measured for E_{d} = 14.7 MeV are analyzed by DWBA to yield S_{α}, a measure of the composition ^{8}Be + α in the wave function of ^{12}C_{g.s.}. Subject to an uncertain normalization, S_{α} is found to be close to unity (1964DA1B, 1966DA1C, 1966DE09).
Angular distributions of elastically scattered tritons have been determined at E_{t} = 1.0 to 1.75 MeV (1962GU01: see also (1968HE1N)), at 6.4, 6.8 and 7.2 MeV (1964PU01) and at 12 MeV (1965GL04: optical model analysis; see also (1966GL1B)).
Angular distributions of elastically scattered ^{3}He particles have been determined for E(^{3}He) = 2 to 6 MeV (1966SC12), 5.5 MeV (1961PA04), 8.5 and 10 MeV (1966SC22), 12 MeV (1965YO1B), 12.0 to 18.6 MeV (1967FO1F), 20.1 MeV (1967MA1G: also ^{12}C*(4.4)), 24.5, 25.3 and 26.8 MeV (1964SE05), 25.7 MeV (1966DA1H: also ^{12}C*(4.4, 7.7)), 26.1 to 32.6 MeV (1963PA15: also ^{12}C*(4.4)) and 29  30 MeV (1961AG1A, 1961CA18, 1962AG01, 1962CA29, 1962GA17, 1965BU1H, 1967BA2P, 1967BR1N). See also (1961FO02, 1962WE1C, 1967AR17, 1967AS1B) and (1961HO1J, 1964GO1J, 1965FR1E, 1967GR1N, 1967PA1U; theor.). For reaction (b) see (1965DO1H).
Angular distributions of elastic and inelastic αparticles and of 4.43 MeV γrays have been measured at a number of energies: see Table 12.24 (in PDF or PS). DWBA fits to differential cross sections observed at 40.5 MeV for Q = 4.4 yield B(E2)(↓) = 13 e^{2} · fm^{4}; for Q = 9.6, B(E3)(↓) = 50  70 e^{2} · fm^{6} (1966HA19). Except for the broad 10.1 MeV state all known levels of ^{12}C with E_{x} < 14 MeV have been observed by (1966HA19). Angular distributions of αparticles and 4.4 MeV γrays have been studied at E_{α} = 22.5 (1964EI01) and at 43 MeV (1959SH62, 1962MC11). The studies of (1962MC11, 1964EI01) yield information on the polarization of the ^{12}C*(4.4) as produced in inelastic scattering. The derived polarizations show strong dependence on scattering angle and are not explained by simple PWBA or adiabatic reaction mechanisms: DWBA gives qualitative agreement. Similar studies involving ^{12}C*(9.6) confirm that J^{π} = 3^{} (1963LA07). See also (1959CA14, 1962BR14, 1964BU1F, 1964LA07, 1967VE1C) and (1959BL31, 1959GL57, 1960RO1E, 1961EI1A, 1962RE1C, 1963DA1B, 1963HO1J, 1964DA1D, 1964GR1L, 1965JA1D, 1966JO1A, 1967BO1W, 1967JA1G, 1967LA1K; theor.) and (1959AJ76). The 9.6 MeV state decays predominantly through ^{8}Be_{g.s.} (1966BO28). The angular distribution of alphas corresponding to ^{12}C*(12.7; J^{π} = 1^{+}) at E_{α} = 28.5 MeV is not accounted for in DWBA. A spinorbit interaction leading to spin flip appears to be involved (1967NA06). For reaction (b) see (1953LI28). Angular correlations in ^{12}C(α, 2α) (reaction (c)) observed at E_{α} = 915 MeV give evidence for strong αclustering in ^{12}C (1961GO1T). See also (1961VA38, 1962BR14, 1962VA25, 1965YA02).
See (1964OL1A); see also (1963BE1R, 1966DE09, 1967SI1C).
See (1964OL1A). See also (1963SH1E) for reaction (a) and (1963SA1E) for reaction (b).
At E(^{12}C) = 126 MeV, strong inelastic peaks corresponding to ^{12}C*(0, 4.4, 14.0 ± 0.5) have been observed. Groups with Q = 9 and 19 MeV are also seen. Their interpretation is less clear. Angular distributions suggest that the 14 MeV state has J^{π} = 4^{+}; the large intensity indicates close association with ^{12}C_{g.s.} (1962WA24, 1963GA05, 1966BA2K); deformation parameters are listed by (1966BA2K); see also (1962GA02, 1962WI09). The elastic scattering has also been studied for E_{c.m.} = 3 to 13.4 MeV (1961BR15) and at E_{c.m.} = 56.7 MeV (1962SM02). See also (1965GR1F), (1959AL1H, 1962BE43, 1962SE1G, 1963WI1G) and (1962BU1B, 1963BA1Y).
Differential cross sections have been determined for the ^{12}C_{g.s.} transition at E(^{14}N) = 21.5 to 27.3 MeV (1960HA16) and at E_{c.m.}(^{14}N) = 62.5 MeV (1962SM02); those to the 4.4 MeV state have been measured at E(^{14}N) = 27.3 MeV (1961HA04). See also (1961KU1D, 1961NE04, 1962WI09) and (1963KU1L).
Differential cross sections have been determined for the ^{12}C_{g.s.} transition at E_{c.m.}(^{16}O) = 8 to 13.7 MeV (1963KU12) and at E(^{16}O) = 35 (1967GO1A, 1968VO1D), 42 (1964NE01), 67 (1959MC1D) and 168 MeV (1964HI09): those to the 4.4 MeV state have been measured at E(^{16}O) = 42 and 168 MeV (1964HI09, 1964NE01). A DWBA analysis of the 168 MeV data is given by (1966BA2K). See also (1963KU1L, 1967AB1D).
The elastic scattering angular distributions in both (a) and (b) have been measured at E = 35 MeV (1967GO1A).
The decay is mainly to the ground state via an allowed transition. Branching fractions to other states of ^{12}C are listed in Table 12.25 (in PDF or PS). The halflife is 10.97 ± 0.04 msec; see Table 12.28 (in PDF or PS). Since transitions to ^{12}C_{g.s.} and ^{12}C*(4.4) are allowed, J^{π}(^{12}N) = 1^{+}. See discussion of ^{12}B(β^{}) and (1965WU1A). See also (1962PO02, 1966DU1E, 1967HU10).
See ^{13}C.
Angular distributions of deuterons to ^{12}C*(0, 4.4) have been measured by (1966GL01: 8 and 12 MeV) and by (1961BE12: 17 MeV). For the ground state, θ^{2} = 0.036 at E_{p} = 8 MeV and 0.058 at 12 MeV; for the 4.4 MeV state θ^{2} = 0.051 at 12 MeV (1966GL01: PWBA). See also (1960NE1C, 1964TE1G). At E_{p} = 54.9 MeV, strong deuteron groups are observed to ^{12}C*(0, 4.4, 12.7, 15.1, 16.1) and partial angular distributions of these groups have been observed. Spectroscopic factors (from DWBA) indicate that the summed transition strengths to the four excited states are approximately equal to the P_{3/2} neutron pickup strength in ^{12}C(p, d) (1968TA1V).
Angular distributions of tritons have been obtained by (1954HO48: 2.2 and 3.3 MeV; t_{0}), (1966GL01: 8 and 12 MeV; t_{0} and t_{1}), (1960MA10: 14.8 MeV; t_{0}, t_{1}, t_{2}). The relative θ^{2} for the ground and first two excited states are 1 : 0.76 : 0.039 (1960MA10, 1966GL01: PWBA). Assuming θ^{2} = 0.031 for ^{12}C_{g.s.}, θ^{2} = 0.024 for ^{12}C*(4.4) and 0.0012 for ^{12}C*(7.7) (1960MA32). See also (1959KU1C, 1963OG1A, 1965DE26, 1967DE1J).
Angular distributions have been determined at many energies: see (1962CH02: 1.6 to 3.3 MeV; α_{0}, α_{1}, α_{2}), (1968MI1H: 1.66 to 3.12 MeV; α_{0}, α_{1}, α_{2}), (1957HO63: 2 MeV; α_{0}, α_{1}), (1960BA25: 1.8 MeV; α_{0}), (1957HO62: 4.5 MeV; α_{0}, α_{1}), (1964DE1E, 1965DE26: 8.8, 9.4, 10.3 MeV; α_{0}, α_{1}; DWBA), (1966KE08: 12, 15, 18 MeV; α_{0}, α_{1}, α_{2}, α_{3}, α_{5}, α_{6}, α_{7}, α_{8}; DWBA), (1967BA2G: 40  45 MeV). (1966KE08) find l = 1 or 0 for all the groups except α_{3} (to ^{12}C*(9.6)) for which l = 2. Angular correlations of αparticles and 4.4 MeV γrays have been studied at E(^{3}He) = 4.5 MeV (1962HO13). See also (1968NO1E). The 15.1 MeV γray has been observed: see (1957BR18, 1959AL96, 1959BR79). See also (1959OW1A, 1961HO1F, 1964EL1B, 1965NE1B, 1967BH1B).
At E_{p} = 18.5 MeV, the angular distribution of the tritons to the ground state has been determined: l = 0 (1961LE1A, 1963LE03).
Not reported.
At E_{n} = 1415 MeV, the angular distribution of the tritons to the ground state has been fitted with L = 2 (1967AN08, 1967FE06, 1967LI06, 1967RE01). See also (1959GA14, 1967BA1E, 1967MO21).
At E_{p} = 40 MeV, angular distributions of the ^{3}He to ^{12}C*(0, 4.4) have been determined. They show strong forward peaking (1966BR1X, 1966HO1F). See also (1961CL09, 1962MA1L, 1967HO1N).
Alpha groups have been observed corresponding to all ^{12}C states up to ^{12}C*(16.11), with the exception of ^{12}C*(10.3) and ^{12}C*(14.7) (see (1965BR08)). See Table 12.26 (in PDF or PS) for a listing of energy parameters measurements. Angular distributions have been obtained at many energies: see (1966EU01: 0.5 to 2.2 MeV; α_{0}), (1961SJ1B: 0.6 to 0.8 MeV; α_{0}), (1965WI11; 0.8 to 1.9 MeV; α_{0}, α_{1}), (1965ST02: 0.9 to 1.2 MeV; α_{0}, α_{1}), (1960KA1H: 1.4 to 2.9 MeV; α_{0}), (1961IS03: 1.5 to 3 MeV; α_{0}), (1965SC12: 4 MeV; α_{0}, α_{1}, α_{2}, α_{3}, α_{5}, α_{6}, α_{7}; 7.2 MeV; α_{7}, α_{8}, α_{9}, α_{11}), (1965BR08: 5.9 and 7.2 MeV; α_{7}, α_{11}, α_{12}), (1964CH1C: 4, 6, 8 and 10 MeV; α_{0}, α_{1}, α_{2}), (1962WI05: 10 MeV; α_{0}, α_{1}), (1960HU10: 10.3 to 11.4 MeV: α_{0}, α_{1}), (1966DR04: 11.3 and 12.6 MeV; α_{0}, α_{1}), (1961YA08: 14.7 MeV; α_{0}, α_{1}), (1959BO40, 1959HE1C: 20.0 MeV; α_{0}), (1959FI30: 20.9 MeV; α_{0}, α_{1}, α_{3}), (1965PE17: 24 MeV; α_{0}, α_{1}, α_{2}, α_{3}), (1966VI1A: 28.5 MeV; α_{1}). Integrated cross sections for eight alpha groups have been obtained at E_{d} = 11.8 MeV (1966JA05). At E_{d} = 24 MeV, α_{1} is strongly favored over α_{0}, and α_{3} is favored over α_{4}. For α_{0}, α_{1} L = 2 is preferred (1965PE17). Angular distributions at E_{d} = 4 MeV are nearly symmetric about 90°, suggesting a compound nucleus process involving many overlapping levels (1965SC12). In a test of isospin conservation, (1965BR08) find, at E_{d} = 7.2 MeV, the cross section for excitation of ^{12}C*(15.11, J^{π} = 1^{+}; T = 1) = 31% of that for ^{12}C*(12.71, J^{π} = 1^{+}; T = 0); σ(16.11)/σ(12.71) = 4%. Violation of this order can be understood as being due to coulomb mixing in the compound nucleus. Comparison of angular distributions of ^{14}N(d, α)^{12}C at E_{d} = 20 MeV and ^{12}C(α, d)^{14}N at E_{d} = 41.7 MeV suggest an upper limit of 3% for the time reversal nonconserving fraction of the Hamiltonian (1959BO40, 1959HE1C, 1965PE17). See also (1962AL09, 1966ME1E). At E_{d} = 1.8 MeV, the alpha particles to the 7.65 MeV state were observed in coincidence with recoiling ^{12}C_{g.s.} nuclei. If Γ_{rad} ≡ (Γ_{γ} + Γ_{π}), the ratio Γ_{rad}/Γ = (2.8 ± 0.3) × 10^{4}: see ^{12}B(β^{})^{12}C (1963SE23). See also (1967UI01).
At E_{α} = 42 MeV, angular distributions of ^{6}Li ions corresponding to the ground and first excited states of ^{12}C have been measured (1964ZA1A). See also (1964BR1L).
See (1965SH1A).
Searches for double dipole deexcitation of the 4.4 MeV state have been unsuccessful Γ_{E1E1}/Γ_{E2} ≤ 0.5 × 10^{4} (1964AL18), ≤ 1.7 × 10^{4} (1960MC03). A theoretical estimate of 10^{8} is cited by (1960MC03). Angular distributions of αparticles leading to the ground and 4.4 MeV states have been determined for E_{p} up to 18.6 MeV: (see (1963MI1H, 1963RO01, 1964EC03, 1965WA1N, 1967NO02)). At the higher energies the groundstate alpha particles show marked backward peaking, in agreement with the inverse reaction ^{12}C(α, p)^{15}N (1964EC03). See also (1963NA1C, 1964HO1D, 1966EV1B).
Angular distributions of the ^{7}Li ions to the ground and 4.4 MeV states have been determined at E_{α} = 42 MeV (1966MI1M).
There is evidence for the involvement of many ^{12}C states: see (1965RO05, 1967CA1C).
For reaction (a), see (1963MO04, 1964MO1D). In reaction (b), 4.4 MeV γrays are observed at E_{p} = 146 (1962FO03) and 150 MeV (1962RO25). See also (1957CH1A, 1964BA1C, 1965ZH1A, 1967CH04, 1967FU1A). In reaction (c), the angular distributions 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. The angular distributions and integrated cross sections vary strongly with energy (1965BR13). See also (1962DO1B, 1962ZU01, 1965KU1B, 1965ZE1B, 1967PA1T, 1967TA1C, 1968YA1C).
At E_{d} = 14.6 MeV, the ground state angular distribution suggests that direct interaction predominates (1964DA1B). Qualitative agreement with DWBA is reported (1966DA1C). See also (1963DR1B, 1964BL1C, 1965SL1C).
See (1967ZA1B).
See (1966GA10).
See (1967DE03).
See (1963DE02).
See (1962FO03).
Groundstate angular distributions have been measured at E_{d} = 9 to 14.5 MeV (1964DA1B, 1967DE03, 1967DE14).
See (1967DE14).
The αinduced fission of ^{20}Ne has been studied by (1962LA03, 1962LA05, 1962LA15). See also (1963HO1H, 1963TA1B).
