A=12C (1975AJ02)

1. (a) ⁶Li(⁶Li, n)¹¹C Q_m = 9.453 E_b = 28.175
(b) ⁶Li(⁶Li, p)¹¹B Q_m = 12.218
(c) ⁶Li(⁶Li, d)¹⁰B Q_m = 2.987
(d) ⁶Li(⁶Li, α)⁸Be Q_m = 20.808
(e) ⁶Li(⁶Li, nα)⁷Be Q_m = 1.908
(f) ⁶Li(⁶Li, pα)⁷Li Q_m = 3.552
(g) ⁶Li(⁶Li, 2α)⁴He Q_m = 20.900

For E(⁶Li) = 1.2 to 2.8 MeV, population ratios of ⁷Be*(0.43), ⁷Li*(0.48) and ¹⁰B*(0.72) (reactions (c), (e) and (f)) remain approximately constant. Simple tunneling or compound nucleus models are not compatible with the data and a direct interaction through long-range tails is suggested (1962MC12). Absolute reaction cross sections at E(⁶Li) = 2.1 MeV are in reasonable agreement with estimates based on barrier penetration. A strong preference for α-emission suggests that the favored mechanism involves interacting clusters (1963HU02). The α₀ yield (0°) (reaction (d)) shows two broad peaks at E(⁶Li) = 4 and 9 MeV (1967CA1D: prelim. results; E(⁶Li) = 2 to 14.5 MeV) while (1970FR06: E(⁶Li) = 4 to 24 MeV) report a broad peak at E(⁶Li) ≈ 10 MeV. The yield of ⁶Li + ⁶Li → 3α (reaction (g)) for E(⁶Li) = 4 to 20 MeV is dominated by a broad resonance (Γ = 5 MeV) at the Coulomb barrier, which is consistent with the formation of a quasi-molecular state ⁶Li + ⁶Li with τ ≈ 10^-21 sec (1970FR06). A multiparameter coincidence study of reaction (g) for E(⁶Li) = 2 to 13 MeV shows the importance of direct interactions: the data were fitted assuming an (α + d) cluster structure for ⁶Li and an interaction potential acting only between the two deuterons (1971GA1N, 1971GA21, 1972GA32). See also (1971WY01), (1968AJ02) for the earlier work, ⁸Be and ¹⁰B in (1974AJ01) and ¹¹B and ¹¹C for reactions (a) and (b).

2. (a) ⁶Li(⁶Li, ⁶He)⁶Be Q_m = -7.797 E_b = 28.175
(b) ⁶Li(⁶Li, ⁶Li)⁶Li

The elastic scattering (reaction (b)) follows the Mott formula at low energies [≲ 4.0 MeV] (1966PI02: E(⁶Li) = 3.2 to 7.0 MeV). A broad structure is observed in the excitation functions [θ_c.m. = 60° and 90°] at E(⁶Li) ≈ 13 MeV (1973GR34) and ≈ 26 MeV [Γ ≈ 7 MeV] (1971FO08: θ_c.m. = 90°; E(⁶Li) to 34 MeV). The elastic scattering appears to be dominated by absorption (1971FO08). See also (1973GO01). Excitation functions for the transitions to ⁶Li^*_3.56 + ⁶Li^*_3.56 have been measured for E(⁶Li) = 28.0 to 33.0 MeV (1970NA02: θ_c.m. = 90°) and 28.0 to 36.0 MeV (1973WH02: θ_c.m. = 88°). See also ⁶Li in (1974AJ01). For reaction (a) see ⁶He in (1974AJ01).

3. ⁶Li(⁷Li, n)¹²C Q_m = 20.924

At E(⁷Li) = 2.6 MeV, population of ¹²C*(4.44, 15.11) is reported (1962BE24).

4. ⁹Be(³He, γ)¹²C Q_m = 26.2801

(1970BL09) had reported the observation of a capture resonance at E(³He) = 1.74 MeV which subsequently decayed via ¹²C*(15.11) and which was assumed to correspond to the first J^π = 0⁺; T = 2 state in ¹²C [E_x = 27.585 ± 0.005 MeV]. However, neither (1972HA63) nor (1972WA18) have been able to repeat this measurement: Γ_³HeΓ_γ/Γ < 1.5 meV (1972WA18), < 2 meV (1972HA63). See also (1974HA1G). Excitation functions and angular distribution studies have been carried out by (1972BL17: E(³He) = 1.0 to 6.0 MeV; γ₀, γ₁, γ₂), (1972LI29: 1.5 to 11 MeV; γ₀, γ₁, γ₂, γ₃), (1964BL12: 2 to 4.5 MeV; γ₀, γ₁) and (1974SH01: 3 to 21 MeV (γ₂), to 24 MeV (γ₀), to 26 MeV (γ₁, γ₃)). Observed resonances are shown in Table 12.10 (in PDF or PS).

¹²C*(28.2) appears to be formed by s- and d-wave capture. The γ₀ and γ₂ transitions to the 0⁺ states ¹²C*(0, 7.7) are strong and show a similar energy dependence. A strong non-resonant contribution is necessary to account for the γ₁ yield (1972BL17). The resonance structure reported by (1974SH01) appears to confirm the role of 3p - 3h configurations for ¹²C excitations somewhat above the giant resonance region. The γ₃ yield is relatively unstructured (1972LI29, 1974SH01: to E(³He) = 26 MeV).

5. (a) ⁹Be(³He, n)¹¹C Q_m = 7.558 E_b = 26.2801
(b) ⁹Be(³He, p)¹¹B Q_m = 10.3229
(c) ⁹Be(³He, 2n)¹⁰C Q_m = -5.566

Excitation functions for neutrons have been measured for E(³He) = 1.2 to 9.9 MeV for several neutron groups: see (1968AJ02) for a listing of the earlier references. 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(³He) ≈ 2 MeV: E_x = 27.8 MeV (1965DI06, 1963DU12). The total cross section for ¹¹C production rises monotonically for E(³He) = 0.60 to 1.15 MeV (1973SU07) and then shows a broad maximum, σ = 113 mb, at E(³He) = 4.3 MeV (1966HA21: E(³He) = 3.2 to 10 MeV). Polarization measurements have been carried out for E(³He) = 2.1 to 3.9 MeV (1971TH15: n₀, n₁, n₂₊₃): the shapes of the measured angular distributions for n₀ and n₁ show very gradual changes with energy. It is suggested that a significant direct interaction contribution is present (1971TH15). See also (1970KR09) and ¹¹C.

Excitation functions and angular distributions for protons (reaction (b)) have been measured for E(³He) = 1.0 to 10.2 MeV for a number of proton groups: see (1968AJ02) for a listing of the earlier references. The yields of ten proton groups have been determined for E(³He) = 0.50 to 1.10 MeV (θ = 110°): the yields increase monotonically (1971ST1H, 1973SU07). The excitation curves at higher energies show only a slow and smooth increase: see, e.g. (1960HI08). See also ¹¹B. The excitation function for reaction (c) has been measured from threshold to E(³He) = 31 MeV (1974MO23).

6. (a) ⁹Be(³He, d)¹⁰B Q_m = 1.0916 E_b = 26.2801
(b) ⁹Be(³He, t)⁹B Q_m = -1.0860

The cross section for ground state tritons (reaction (b)) increases monotonically for E(³He) = 2.5 to 4.2 MeV (1969OR01: θ = 40°) and then shows a broad maximum at E(³He) ≈ 4.5 MeV (1967EA01: θ = 20°). For reaction (a) see (1967CR04). See also ⁹B and ¹⁰B in (1974AJ01).

7. ⁹Be(³He, ³He)⁹Be E_b = 26.2801

The elastic scattering excitation function decreases monotonically for E(³He) = 4.0 to 9.0 MeV (1967EA01: θ = 45°) and 15.0 to 21.0 MeV (1972MC01: θ_c.m. = 90°). At θ_c.m. = 111° a slight rise is observed for E(³He) = 19 to 21 MeV (1972MC01). See also (1974BO38: E(³He) = 1.2 to 2.5 MeV). Polarization measurements are reported at E(³He) = 18 MeV (1972MC01) and 31.4 MeV (1971EN03). See also ⁹Be in (1974AJ01).

8. (a) ⁹Be(³He, α)⁸Be Q_m = 18.9134 E_b = 26.2801
(b) ⁹Be(³He, 2α)⁴He Q_m = 19.005

Excitation functions at θ = 140° (reaction (a)) do not show resonant behavior for E(³He) = 1.0 to 1.9 MeV (1970EH1A: α₀, α₁; unpublished work). For reaction (b) see ⁸Be in (1974AJ01) and (1972TA04). See also (1971OS05; theor.).

9. ⁹Be(³He, ⁶Li)⁶Li Q_m = -1.895 E_b = 26.2801

The excitation functions for E(³He) = 4 to 10 MeV (1969TA05: θ = 50°; 1972YO02: θ_c.m. = 32°, 90°) show some fluctuations. See also ⁶Li in (1974AJ01).

10. ⁹Be(α, n)¹²C Q_m = 5.702

Neutron groups have been observed to ¹²C*(0, 4.4, 7.7, 9.6, (10.1), (10.8)). Angular distributions of neutron groups have been measured at many energies in the range E_α = 1.9 to 23 MeV: see (1968AJ02) for earlier references and (1969KL09: E_α = 1.75 and 1.96 MeV; n₀), (1970VA23: E_α = 2.55 to 7.87 MeV (n₀); 2.55 to 7.47 MeV (n₁); 4.36 to 7.47 MeV (n₂)), (1972OB01: 3.21 to 6.44 MeV (n₀, n₁, n₂); 6.24 and 6.44 MeV (n₃)) and (1968VE06: 6.79, 7.96, 8.91, 9.92 MeV; n₀, n₁, n₂).

The mean life of ¹²C*(4.4) [J^π = 2⁺] is 57⁺²³_-17 fsec, Γ_γ = (11.5⁺⁵_-3.2) meV (1966WA10): see Table 12.9 (in PDF or PS). ¹²C*(7.7) decays predominantly into ⁸Be + α (see reactions 20 and 35), J^π = 0⁺, Γ_π/Γ = (6.9 ± 2.1) × 10^-6 (1960AL04, 1972OB01).

See (1959AJ76, 1968AJ02) for surveys of the earlier work. See also ¹³C in (1976AJ04) and (1968LE24, 1969KL1C, 1969NO01, 1969ZI1A, 1970FO1C, 1970GE1A, 1972DA32, 1972DE10, 1973TY1A, 1973VI1C, 1973WE03) and (1968VA1E, 1969HO34; theor.).

11. ⁹Be(⁶Li, t)¹²C Q_m = 10.486

At E(⁶Li) = 23.8 MeV strong transitions are observed to ¹²C*(0, 4.4, 7.7, 9.6, 14.1) (1970OG1A; unpublished). See also (1968JA08) and (1972RI1C; theor.).

12. ¹⁰Be(³He, n)¹²C Q_m = 19.468

At E(³He) = 13 MeV neutron groups are observed to ¹²C*(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 ¹²C (1974GO23).

13. ¹⁰B(d, γ)¹²C Q_m = 25.1885

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 2.91 MeV. The non-resonant yield of 15 MeV γ-rays is due to direct capture process or to a very broad resonance: no sharp resonances are observed corresponding to the T = 2 state reported in reaction 4 [Γ_d₀Γ_γ/Γ ≲ 0.2 eV] (1970BL09, 1974HA1G). Upper limits to the differential cross sections for γ₀ and γ₁ are 5 nb/sr and 50 nb/sr, respectively for E_d = 4.0 to 20.2 MeV (1971SH1E; prelim. results).

14. ¹⁰B(d, n)¹¹C Q_m = 6.467 E_b = 25.1885

The thin-target 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 (1967DI01). The excitation function for the neutrons to ¹¹C*(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 ¹¹C and ¹¹B [n₀/p₀] have been measured for E_d = 1.0 to 2.0 MeV by (1973BR24).

Polarization measurements have been carried out for E_d = 1.20 to 2.90 MeV (1968BR26: n₀) and 2.4 to 4.0 MeV (1972ME06: n₀, n₁, n₂₊₃). The transitions to ¹¹C*(0, 4.32 + 4.80) appear to involve a direct reaction mechanism (1972ME06). See also (1969DI08) and ¹¹C.

15. ¹⁰B(d, p)¹¹B Q_m = 9.2314 E_b = 25.1885

Absolute yields have been measured for various proton groups for E_d = 0.14 to 12 MeV: see (1968AJ02) and (1972AR31: E_d = 0.7 to 2.5 MeV; p₀ → p₃) and (1970BL09: E_d = 2.605 to 2.960 MeV; p₀ → p₃). See also (1970PO03). No clear resonance structure is observed. There is some indication that a broad resonance, corresponding to ¹²C*(27.1) affects the p₁ and p₃ yields (1964BR1A). Upper limits for the partial widths (p₀ → p₃) of the T = 2 state reported in reaction 4 are given by (1970BL09). See also (1972AH1A). For a study of the branching ratio n₀/p₀ see reaction 14 (1973BR24).

Polarization measurements have been carried out recently for E_d = 1.15, 1.40 and 1.85 MeV (1969DI08; p₀), 10 MeV (1969CU10: p₀) and 10 and 12 MeV (1970FI07, 1972FI1E: p₀) and 13.6 MeV (1967GO27: p₀). For earlier polarization studies [E_d = 6.9 to 21 MeV] see (1968AJ02). See also (1967GO27, 1967SA06), (1970DE35, 1973CO18; theor.) and ¹¹B.

16. ¹⁰B(d, d)¹⁰B E_b = 25.1885

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 ¹⁰B*(1.74, 2.16) [J^π = 0⁺; T = 1 and J^π = 1⁺; T = 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_2.15 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_d = 9, 10 and 11 MeV (1972FI1E, 1973FI1C) and at 15 MeV (1974BU06). See also ¹⁰B in (1974AJ01).

17. (a) ¹⁰B(d, t)⁹B Q_m = -2.178 E_b = 25.1885
(b) ¹⁰B(d, ³He)⁹Be Q_m = -1.0916

For polarization measurements at E_d = 15 MeV involving ⁹Be*(0, 2.43) and ⁹B*(0, 2.36) see (1974LU06). See also ⁹Be and ⁹B in (1974AJ01).

18. (a) ¹⁰B(d, α)⁸Be Q_m = 17.822 E_b = 25.1885
(b) ¹⁰B(d, 2α)⁴He Q_m = 17.9138

Excitation functions have been measured for the α₀ and α₁ groups for E_d = 0.4 to 3.3 MeV: see (1968AJ02) for earlier references and (1968FR07: 0.5 to 2.0 MeV), (1968CO31: 0.8 to 2.5 MeV) and (1970BL09: 2.605 to 2.960 MeV). The α₀ yield has also been measured for E_α = 4 to 12 MeV by (1971RE1D) and the yields to ⁸Be*(16.6, 16.9) have been determined for E_d = 2.856 to 2.906 MeV by (1972AH1A; in 2 keV steps; unpublished). A number of broad maxima are observed in the excitation curves above E_d = 1 MeV. The α₀ yield shows such a maximum at E_d = 1 MeV which (1968FR07) attribute to an s-wave resonance corresponding to a state with E_x ≈ 26.0 MeV, Γ ≈ 0.5 MeV. No evidence for the T = 2 state reported in reaction 4 was found in the α₀ and α₁ yield curves taken in 2 keV steps for 27.35 < E_x < 27.65 MeV (1970BL09). See also (1972AH1A). The relative populations of ⁸Be*(17.6, 18.1) have been determined for E_d = 4 to 12 MeV (1970CA12): see ⁸Be, reaction 38 (1974AJ01). For reaction (b) see (1968AS01, 1973RO28) and ⁸Be in (1974AJ01). See also (1967LE1C, 1967NA11) and (1970KO01, 1970KO27, 1971LA25; theor.).

19. ¹⁰B(d, ⁶Li)⁶Li Q_m = -2.987 E_b = 25.1885

This reaction has been studied for E_d = 8 to 13.5 MeV (1964GE10).

20. (a) ¹⁰B(³He, p)¹²C Q_m = 19.6948
(b) ¹⁰B(³He, pα)⁸Be Q_m = 12.328
(c) ¹⁰B(³He, 2p)¹¹B Q_m = 3.738
(d) ¹⁰B(³He, pn)¹¹C Q_m = 0.973

Proton groups observed by (1958MO99, 1959AL96, 1962BR10) are displayed in Table 12.11 (in PDF or PS). Angular distributions of many of these groups have been measured for E(³He) = 1.4 to 14 MeV: see (1968AJ02) for the earlier references and (1970BE1F).

From studies of ¹⁰B(³He, pα)⁸Be it is determined that ¹²C*(7.7, 9.6, 10.8, 14.1, 16.1) have natural parity π = (-1)^J, and that ¹²C*(11.8, 12.7, 13.3), which decay only to ⁸Be*(2.9) and not to the ground state, have unnatural parity: see Tables 12.8 (in PDF or PS) and 12.11 (in PDF or PS), and (1968AJ02). ¹²C*(12.7) decays also by γ-emission: the cascade via ¹²C*(4.4) is 15 ± 4%, the crossover transition is 85 ± 4% (1972AL03); Γ_γ/Γ_α = 2.5 ± 1% (1958MO99, 1959AL96). ¹²C*(15.11) [J^π = 1⁺; T = 1] decays by γ-emission to ¹²C*(0, 4.4, 7.7, (10.3), 12.7): see Table 12.9 (in PDF or PS) (1972AL03). It is suggested by (1972AL03) that an isospin-forbidden α-decay branch from ¹²C*(15.11) to ⁸Be*(2.9), which had been reported with an intensity of (1.2 ± 0.7)% in reaction 67, does not exist: the problem might have been an inaccurate determination of the intensity of the γ-branch to ¹²C*(12.7) by (1970RE09): see, however, (1974BA42) in reaction 67.

¹²C*(16.11, 16.58) show decay to both ⁸Be*(0, 2.9). The consequent assignment of natural parity is consistent with J^π = 2⁺ for the former but not with J^π = 2^- for the latter. For ¹²C*(16.11) observed values of Γ_α₀/Γ are 0.05 - 0.12; the decay to 3α occurs rarely if at all (1966WA16).

Reactions (c) and (d) have been studied by (1970BO39). The latter, at E(³He) = 11 MeV, appears to proceed via a state in ¹²C 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 ¹²C states with 20 < E_x < 25 MeV via channels (c) and (d) is estimated. The α₀ decay is very small, consistent with the expected population of T = 1 states (1970BO39).

See also ⁸Be in (1974AJ01), ¹³N in (1976AJ04) and (1968KR02, 1970BE1F, 1972BE05, 1974AN19), (1967HO1C) and (1967PR1B; theor.).

21. ¹⁰B(α, d)¹²C Q_m = 1.3409
Q₀ = 1340.6 ± 1.5 keV (1967BR1B).

At E_α = 21.2, 23.0 and 25.0 MeV angular distributions of the deuterons to ¹²C*(0, 4.4) have been measured (1967AL16). The (dγ_4.4) angular correlations have been measured for E_α = 19 to 25 MeV (1972EL09). See also (1967SP09, 1973HA1Y, 1973SP1D), (1971BU1K, 1973ZE03; theor.) and ¹⁴N in (1976AJ04).

22. ¹⁰B(⁶Li, α)¹²C Q_m = 23.715

At E(⁶Li) = 4.9 MeV angular distributions have been obtained for the α-particles to ¹²C*(0, 4.4, 7.7, 9.6). The population of ¹²C*(11.8, 12.7) is also reported (1966MC05), as is that of ¹²C*(15.11) [T = 1] (1964CA18: E(⁶Li) = 3.8 MeV): the intensity ratio α_15.1/α_12.7 = 3 ± 2%. See also (1969CO1D, 1970GI05).

23. ¹⁰B(¹⁴N, ¹²C)¹²C Q_m = 14.916

Angular distributions involving ¹²C^*_4.4 + ¹²C_g.s. and ¹²C^*_4.4 + ¹²C^*_4.4 have been measured at E(¹⁴N) = 22.5 and 30 MeV (1969IS01). See also (1972VO02).

24. ¹⁰B(¹⁶O, ¹⁴N)¹²C Q_m = 4.452

Angular distributions involving ¹⁴N_g.s. + ¹²C_g.s. and ¹⁴N_g.s. + ¹²C^*_4.4 have been measured at E(¹⁶O) = 30 and 32.5 MeV and also at 26 MeV for the double ground state transition (1969IS01). See also (1968OK06).

25. (a) ¹¹B(p, γ)¹²C Q_m = 15.9572
(b) ¹¹B(p, α)⁸Be Q_m = 8.591 E_b = 15.9572
(c) ¹¹B(p, α)⁴He⁴He Q_m = 8.6824

In view of the complexity of the available information on these three reactions, we will first summarize the recent experimental results and then review the evidence for the parameters of ¹²C states observed as resonances.

(a) In the range 4 MeV < E_p < 14.5 MeV σ(γ₀) is dominated by the giant dipole resonance at E_p = 7.2 MeV (E_x = 22.6 MeV, Γ_c.m. = 3.2 MeV), while the giant resonance in γ₁ occurs at E_p ≈ 10.3 MeV (E_x = 25.4 MeV, Γ_c.m. ≈ 6.5 MeV): see (1964AL20). A study of the giant dipole resonance region with polarized protons (E_p = 6 to 14 MeV) sets new limits on the configuration mixing in the γ₀ giant resonance. The analysis of γ₁ is more complicated: the asymmetry results are consistent 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). Measurements of differential cross sections at 90° (E_p = 13 to 22 MeV), of angular distributions (E_p = 7 and 14 to 21 MeV), and of total cross sections (E_p = 14 to 21 MeV) have been reported by (1970BR1J, 1972BR26) for γ₀, γ₁ and γ₃ [to ¹²C*(0, 4.4, 9.6)]: disagreement is reported with the cross section values reported by (1964AL20). The γ₂ yield to ¹²C*(7.7) exhibits a peak at E_p ≈ 14.3 MeV with a cross section ≈ 2.3% that of γ₀. The γ₃ yield shows two large asymmetric peaks at E_p = 12.5 and 13.8 MeV with Γ ≈ 0.7 and 2.5 MeV, respectively, as well as a weaker structure near E_p = 9.8 MeV (1971SN1A: E_p = 6 to 18 MeV; abstracts). (1969KE02: E_p = 13 to 21 MeV) report a broad peak in the γ₀ cross section at E_p = 14.8 MeV [E_x = 29.5 MeV]. The previously reported resonance in γ₀ at E_p = 20.1 MeV [see (1968AJ02)] does not exist: see (1969KE02, 1972BR26). No evidence is seen in this reaction for the J^π = 0⁺; T = 2 state reported in reactions 4 and 12 (1974HA1G: search for γ_12.5 + γ_15.1, that is (0⁺; 2) → (1⁺; 1) → (0⁺; 0)). Work on other resonances is discussed below. See also the reviews by (1968BR1D, 1968SC1B, 1972HA1Y, 1973GL1C, 1973HA1Q, 1973SU1E, 1974HA1N), (1972CA1H) and (1969MA22, 1970GO41, 1973BA05, 1973HA1X, 1973SU03; theor.).

(b) Excitation functions for α₀ have been measured recently for 7.50 < E_p < 18.9 MeV: no marked structure is observed above E_x = 28 MeV (1972TH1C: Ph.D. thesis; (1969TH1B, 1971TH1F); abstracts). See also ⁸Be in (1974AJ01) and (1968CH01, 1971GU23).

(c) This reaction has been studied for E_p = 0.15 to 9.5 MeV. It proceeds predominantly by sequential two-body decay via ⁸Be*(0, 2.9): see ⁸Be in (1974AJ01) and (1968CH01, 1968GI03, 1969QU01, 1970CO03, 1971KO22, 1971YA13, 1972CH35, 1972DZ10, 1972HU04, 1972MI1J, 1972TR07, 1972VO01, 1973PR1C). See also (1969PH1B), (1967CO29, 1967EN1A, 1967FL12, 1968LA1C, 1969LA1B, 1970PA10), (1969GO13, 1969SA1B, 1970GI1C, 1970GO1J, 1970GO33, 1970GO49, 1970KO01, 1970KO1K, 1970KO27, 1970MC25, 1970MC1T, 1970SC01, 1971GO20, 1971LA25, 1972GO1N, 1972KO1J, 1973GO35, 1973KO11, 1973KO38; theor.) and (1974LI1M; applied).

The parameters of the observed resonances are displayed in Table 12.12 (in PDF or PS). The following summarizes the information on the low-lying resonances: for a full list of references see (1968AJ02).

E_p = 0.16 MeV [¹²C*(16.11)]. This is the J^π = 2⁺; T = 1 analog of the first excited states of ¹²B and ¹²N. The γ-decay is to ¹²C*(0, 4.4, 9.6): the angular distribution of γ₃, together with the known α-decay of ¹²C*(9.6), fix J^π = 3^- for the latter (1961CA13). A new measurement of the (p, γ) and (p, α) resonant cross sections yields 125 ± 16 μb and 38.5 ± 3.2 mb, respectively, based on Γ_c.m. = 6.7 keV. Γ_γ and Γ_p for ¹²C*(16.11) are then 21.7 ± 3.3 eV and 21.7 ± 1.8 eV, respectively (1974AN19). See also Table 12.9 (in PDF or PS).

E_p = 0.67 MeV [¹²C*(16.58)]. The proton width [Γ_p ≈ 150 keV] indicates s-wave protons and therefore J^π = 1^- or 2^-. This is supported by the near isotropy of the two resonant exit channels, α₁ and γ₁. The α₁ cross section indicates 2J + 1 ≥ 5: therefore J^π = 2^-. [This is consistent with the results of an α - α correlation study via ⁸Be*(2.9) (1972TR07)]. The γ₁ E1 transition has |M|² ≈ 0.01 W.u., suggesting T = 1 (1957DE11, 1965SE06). (1962BL10) report a γ branch to ¹²C*(12.71) (≈ 6% of the intensity of the γ₁ transition). Such a branch may also be present for ¹²C*(17.23). See also (1973PR1C).

E_p = 1.4 MeV [¹²C*(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 α₀ and γ₀: see (1957DE11) and is consistent with the α - α correlation results of (1972TR07). Two solutions for Γ_p are possible; the larger (chosen for Table 12.12 (in PDF or PS)) is favored by elastic scattering data (1965SE06).

E_p = 2.0 MeV [¹²C*(17.76)]. The resonance in the yield of α₀ requires natural parity, the small α-widths suggest T = 1. For J^π = 1^- or 3^- the small γ-widths would be surprising; J^π = 2⁺ would lead to a larger anomaly than is observed. J^π is then 0⁺; T = 1 (1965SE06).

E_p = 2.37 MeV [¹²C*(18.13)]. Seen as a resonance in the yield of 15.1 MeV γ-rays: σ_R = 0.77 ± 0.15 μb, Γ_c.m. = 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 non-resonant background excludes a definite assignment (1972SU08).

E_p = 2.62 MeV [¹²C*(18.36)]. The resonance for α₀ requires natural parity; the presence of a large P₄ 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).

E_p = 2.66 MeV [¹²C*(18.40)] is not seen here: see ¹¹B(p, p).

E_p = 3.12 MeV [¹²C*(18.80)]. The angular distribution of γ₀ indicates E2 radiation, J^π = 2⁺. This assignment is supported by the angular correlation in the cascade γ₁ and by the behavior of σ(α₀); T = 1 is suggested by the small Γ_α (1965SE06).

The structure near E_p = 3.5 - 3.7 MeV [¹²C*(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(α₀) 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(γ₁) (1955BA22) also appear in σ(α₁), but not in σ(α₀). Angular distributions suggest J^π = 2⁺ or 3^- for the latter [¹²C*(20.64)]; the strength of γ₁ and absence of γ₀ favors J^π = 3^-; T = 1 (1963SY01).

The first seven T = 1 states in ¹²B and ¹²C 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 Table 12.13 (in PDF or PS) (1971MO14, 1974AN19).

26. ¹¹B(p, n)¹¹C Q_m = -2.765 E_b = 15.9572

Excitation functions have been reported for E_p = 2.6 to 11.5 MeV. They are characterized by numerous peaks: see Table 12.14 (in PDF or PS). The positions of these appear to correspond with ¹¹B(p, α)⁸Be 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) appears to demand J ≥ 4 (1961LE11).

The polarization transfer coefficient has been measured for E_p = 7 to 15 MeV: the strong influence of resonances is apparent (1974LI1J). See also (1974MA07; theor.). Polarization measurements have been carried out for E_p = 7 to 11 MeV (1965WA04) and at 24.5 MeV (1972MO41). See also (1973BA05; theor.), ¹¹C and (1968AJ02).

27. (a) ¹¹B(p, p)¹¹B E_b = 15.9572
(b) ¹¹B(p, p')¹¹B*
(c) ¹¹B(p, 2p)¹⁰Be Q_m = -11.2294

A pronounced anomaly in the elastic scattering is observed near E_p = 0.67 MeV at all angles; the level is therefore formed by s-waves. The 0.3 to 1.0 MeV results are well accounted for by two resonances: E_p = 0.67 MeV, s-wave, 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 12.14 (in PDF or PS) (1955BA22, 1965SE06, 1971SA1H). Excitation functions for p₀ and p₁ have been measured for E_p = 7.5 to 21.5 MeV: no pronounced structure is observed above E_x = 28 MeV (1972TH1C: Ph.D. thesis; (1969TH1B, 1971TH1F); abstracts).

Polarization measurements have been reported at E_p = 1.9 to 3.0 MeV (1974DE45: p₀), 3.5 to 10.5 MeV (1971SA1H; prelim. report; p₀, p₁), 30.3 MeV (1969KA15, 1971LO05; p₀, p₁, p₂) and 155 MeV (1968GE04; p₀, p₁, p₂, p₄). See also (1965HU10, 1968RI1J, 1972RE06) and (1969WA11, 1971BL1E; theor.). For reaction (c) see (1971RA26). See also ¹¹B and ¹⁰Be in (1974AJ01).

28. ¹¹B(p, d)¹⁰B Q_m = -9.2314 E_b = 15.9572

See ¹⁰B in (1974AJ01).

29. ¹¹B(d, n)¹²C Q_m = 13.7325

Reported neutron groups are displayed in Table 12.15 (in PDF or PS). Angular distributions have been reported for many energies in the range 0.5 < E_d < 11.8 MeV: see (1968AJ02) for a listing of the earlier references and (1970BU15: 5.5 MeV; n₀, n₁), (1967FU07: 6 MeV; see Table 12.15 (in PDF or PS)), (1974AN19: 6 MeV; n to ¹²C*(15.1, 16.1); see Table 12.13 (in PDF or PS)), (1971MU18: 11.8 MeV; see Table 12.15 (in PDF or PS)). See (1971MU18) for a discussion of the problems involved in comparing spectroscopic factors obtained in this reaction and in the (³He, d) reaction [reaction 30].

Angular correlations of neutrons and γ-rays have been studied at many energies: see (1968AJ02) for the earlier references and (1968TE03: 1.6 to 3.3 MeV for γ_4.4; 2.9 and 3.3 MeV for γ_15.1) and (1972TH14: 4.0 to 4.8 MeV; γ_4.4, γ_15.1).

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 γ-rays are observed: E_d = 1.633 ± 0.003 MeV, Γ < 2 keV (1958KA31) [E_x = 15.110 ± 0.003 MeV].

A study of the angular distributions and energy spectra of α-particles from the decay of ¹²C states shows that the 12.71 and 11.83 MeV states decay sequentially via ⁸Be; the former via ⁸Be*(2.9), the latter 90% via ⁸Be*(2.9) and 10% via ⁸Be(0). There is some evidence that the 10.84 MeV state decays primarily to ⁸Be(0). J^π = 3^- for the 9.64 MeV state is favored on the basis of the angular distribution of the α-particles to ⁸Be(0). There is no evidence for direct 3α decay of ¹²C levels in the range E_x = 9 to 13 MeV, nor does ¹²C*(10.3) appear to participate in this reaction (1965OL01).

See also ¹³C in (1976AJ04) and (1970MI1G, 1970YA11; theor.).

30. (a) ¹¹B(³He, d)¹²C Q_m = 10.4634
(b) ¹¹B(³He, np)¹²C Q_m = 8.2388

Observed deuteron groups are displayed in Table 12.15 (in PDF or PS). Angular distributions have been measured at E(³He) = 5.1 to 44 MeV: see (1968AJ02) for the earlier references and (1969MI15: E(³He) = 10, 12 and 18 MeV), (1968BO26: 11 MeV), (1971RE03: 44 MeV). ¹³N*(15.1) [T = 3/2] has been observed to decay to ¹²C*(9.6, 10.8) with branching ratios of 9.6 ± 1.4% and 16.4 ± 3.6%, respectively. The upper limit to ¹²C*(12.7) is ≈ 5% (1974AD1D).

31. ¹¹B(α, t)¹²C Q_m = -3.8574

Angular distributions have been measured at E_α = 15.1, 18.3 and 24.9 MeV (1972VA34: t₀; and t₁ at 24.9 MeV), 27 MeV (1969TE1B: t₀, t₁; unpublished) and 46 MeV (1969FO1C: t₀ → t₃ and t to ¹²C*(12.7); abstracts). See also (1968AJ02). The (t₁, γ) angular correlations have been measured for E_α = 21.2 to 25.0 MeV (1972EL09). See also (1973ZE03; theor.).

32. ¹¹B(⁷Li, ⁶He)¹²C Q_m = 5.979

See (1968ST12).

33. ¹¹B(¹⁴N, ¹³C)¹²C Q_m = 8.407

Angular distributions have been measured for the ground state transition at E(¹⁴N) = 41, 77 and 113 MeV: they show damping of the oscillations with increasing energy (1971LI11). See also (1973DE35; theor.).

34. ¹¹B(¹⁶O, ¹⁵N)¹²C Q_m = 3.829

Angular distributions have been measured at E(¹⁶O) = 27, 30, 32.5, 35 and 60 MeV for the transitions ¹⁵N_g.s. + ¹²C_g.s., ¹⁵N^*_6.3 + ¹²C_g.s., ¹⁵N_g.s. + ¹²C^*_4.4 and ¹⁵N_g.s. + ¹²C^*_9.6 (the latter at E = 60 MeV only) (1972SC03): at the highest energy the ratio θ²/θ²_g.s. for the transition ¹¹B_g.s. + p → ¹²C is 0.12 and 0.05, respectively for ¹²C*(4.4, 9.6). See also (1968OK06), (1969BR1D, 1972MO1E) and (1968VA1D, 1969KA1G, 1970AN1D, 1970SC1G, 1972BO21, 1973DE1W, 1973DE35, 1973OS03, 1974OS1A; theor.).

35. ¹²B(β^-)¹²C Q_m = 13.370

The decay is mainly to ¹²C_g.s.; branching ratios to ¹²C*(4.4, 7.7, 10.3) are shown in Table 12.16 (in PDF or PS). All the observed transitions are allowed. The half-life is 20.41 ± 0.06 msec [see Table 12.2 (in PDF or PS) of (1968AJ02)].

¹²C*(7.7) is of particular interest for helium burning processes in stars [see (1968AJ02)]. The fact that the β-decay is allowed indicates J^π = 0⁺, 1⁺ or 2⁺; it decays primarily by α-emission eliminating J^π = 1⁺, and requiring 0⁺ (1957CO59). (1973BA73) have measured the Q of the α-decay of ¹²C*(7.7) to be 379.6 ± 2.0 keV. When this result is combined with the Q determined from accurate measurements of the E_x of ¹²C*(7.7), the "best" value is Q = 380.1 ± 1.1 keV. This value, together with previously measured values of Γ_π, Γ_π/Γ and Γ_rad/Γ [see Table 12.9 (in PDF or PS)] lead to Γ_rad = 3.41 ± 1.12 meV and to a mean lifetime for the destruction of helium by the [ααα] process of 2.59 x 10^-8ρ²T^-3₉exp(-4.411/T⁹) sec^-1 (1973BA73).

A search for transitions to ¹²C*(12.7) has been unsuccessful (1967AL03). See also reaction 63. For asymmetry measurements see (1967PF02, 1973ST1P, 1974PO05). See also ¹²C, reaction 28 in (1968AJ02), and (1971MI06, 1973CH16, 1973MIYZ, 1974PO05).

36. ¹²C(γ, γ)¹²C

Resonance scattering and absorption by ¹²C*(15.11) have been studied by many groups: see Table 12.15 (in PDF or PS) in (1968AJ02). The partial widths are displayed in Table 12.9 (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 ¹²C*(4.4) is 3.6 ± 0.7% (1970AH02). Elastic scattering to ¹²C*(4.4, 16.1, 17.2) has also been observed. See also (1968AJ02) and Table 12.20 (in PDF or PS).

At higher energies, elastic scattering studies show the giant resonance peak at ≈ 24 MeV. A considerable tail is visible, extending to > 40 MeV (1959PE32). See also reaction 37, (1969MO1H, 1971ME1B) and (1968SI1A; theor.).

37. (a) ¹²C(γ, n)¹¹C Q_m = -18.722
(b) ¹²C(γ, 2n)¹⁰C Q_m = -31.846

The total absorption, mainly (γ, n) + (γ, p), is dominated by the giant resonance peak at 23.2 MeV, Γ = 3.2 MeV [σ_max = 19.8 mb (1965WY02)] and by a smaller structure at 25.6 MeV, Γ ≈ 2 MeV (σ_max ≈ 8 mb): see (1968AJ02) [Tables 12.16 (in PDF or PS), 12.17 (in PDF or PS)] for a detailed listing of the earlier references and results, and see (1973AH1A, 1974BE2B). See also (1967DO1A, 1969BE92). Total absorption cross sections have also been measured at E_γ = 84 to 662 keV by (1968RA1D), at 7.28 and 7.65 MeV by (1969MO1H), at 10 to 140 MeV by (1970AH02, 1972AH1B, 1973AH1A) and at 250 to 1000 MeV by (1972MI1K, 1974HO15). See also Table 12.16 (in PDF or PS) in (1968AJ02).

The (γ, n) cross section shows a giant resonance centered at about 22.5 MeV, Γ ≈ 3 MeV (σ_max ≈ 8 mb), a secondary maximum at 25.5 MeV, Γ ≈ 2 MeV, and a long tail: see (1968AJ02). The giant resonance peak is rather flat-topped with several small fine structure bumps across the top (E.G. Fuller, private communication): see (1966CO09, 1966FU02, 1966LO04, 1971IS09, 1972VA32, 1973BE2F, 1973IS1A, 1974BE2B). The (γ, n₀) cross section has been measured at 90° for 21 < E_x < 40 MeV and compared with the (γ, p₀) cross section (1968WU01): the isospin mixing averages about 2% in intensity and shows structure at the giant resonance. [See the reviews by (1970HA1F, 1973HA1Q).] Angular distributions of n₀ measured over the giant resonance region indicate that the main excitation mechanism is of a 1p_3/2 → 1d_5/2 E1 single particle character. No significant E2 strength is observed (1968RA21, 1970JU1C, 1973JU1C). The fraction of transitions to the ground state and to excited states of ¹¹C has been measured at E_bs = 24.5 to 42 MeV: see ¹¹C (1970ME17), reaction 38 and the discussion in (1973DI1C). For polarization measurements see (1973NA1K) and (1968AJ02). For a listing of recent cross section measurements see Table 12.17 (in PDF or PS).

The cross section for reaction (b) has been measured for E_γ = 35 to 130 MeV. The (γ, 2n) cross section is very 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).

38. (a) ¹²C(γ, p)¹¹B Q_m = -15.9572
(b) ¹²C(γ, π⁺)¹²B Q_m = -152.939
(c) ¹²C(γ, π^-)¹²N Q_m = -156.913

The photo-proton cross section exhibits two broad peaks, the giant resonance peak at 22.4 MeV, Γ = 3.2 MeV, σ_max = 13 mb [see Table 12.19 (in PDF or PS) in (1968AJ02)], and a second broad peak at 25.1 MeV, in addition to some fine structure. 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. Above 24.5 MeV, the ground state (γ, p) and (γ, n) excitation functions have the same shape up to at least 36 MeV (E.G. Fuller, private communication). The (γ, p) results of (1968FR12, 1968FR14, 1969CA22) are in good agreement with those of (1964AL20) for the inverse reaction, ¹¹B(p, γ₀)¹²C [see reaction 25], when the population of ¹¹B*(4.4, 5.0) is taken into account: the required cross sections for the (γ, p₂) and (γ, p₃) processes peak at 1.5 mb at 29 and 30 MeV, respectively (1973DI1C, 1974DI17). The fraction of transitions to the ground and excited states of ¹¹B at several energies in the range E_bs = 24.5 to 42 MeV has been measured by (1970ME17): most of the transitions are to ¹¹B_g.s. and the excited state transitions appear to originate from localized E_x regions. See ¹¹B and the discussions in (1970HA1F, 1973DI1C). Proton spectra and angular distributions have also been measured at E_bs = 50 to 80 MeV (1968MA32, 1969MA23), 98.5 MeV (1968MA19) and 80, 120, 285 and 1140 MeV (1970AN34). The ratio of deuterons to protons has been determined at 1140 MeV by (1972AN1M). For polarization measurements see (1970TO09). See also (1968AJ02) for the earlier measurements and reaction 44.

For reactions (b) and (c) see (1971GR1X, 1972AB1H, 1974BO47, 1974DE1U, 1974EP02) and the "Pion capture and pion reactions" section here.

39. (a) ¹²C(γ, d)¹⁰B Q_m = -25.1885
(b) ¹²C(γ, pn)¹⁰B Q_m = -27.4132

Cross sections and angular distributions of the deuterons corresponding to transitions to ¹⁰B_g.s. and/or low excited states have been measured at E_γ ≈ 40 MeV: the results are consistent with E2. There is some evidence also for the excitation of higher states of ¹⁰B via non-E2 transitions (1972SK08). The high apparent threshold for reaction (a) is thought to reflect the presence of continuum states of ¹⁰B with a high parentage in ¹²C (1964SH1B). For E_bs = 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 (1962CH26). See also (1969AN1F, 1969AN10, 1971AN04, 1971AN15, 1972AN09, 1972AN1M) for excitation functions to 1400 MeV, and (1968AJ02). For reaction (b) see (1968TA10, 1969TA11) and (1973KO1H; theor.).

40. (a) ¹²C(γ, t)⁹B Q_m = -27.366
(b) ¹²C(γ, ³He)⁹Be Q_m = -26.2801

The yield of tritons has been measured for E_γ = 35 to 50 MeV by (1967KR05). See also (1969AN1F, 1972AN09). For reaction (b) see (1969TA11).

41. ¹²C(γ, α)⁸Be Q_m = -7.367

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: see (1964TO1A) and (1968AJ02). For E_γ < 22 MeV, transitions are mainly to ⁸Be_g.s. and ⁸Be*(2.9) with the g.s. transition dominating for E_γ ≲ 14 MeV. For E_γ > 26.4 MeV, ⁸Be (T = 1) levels near 17 MeV are strongly excited (1955GO59). Alpha energy distributions show surprisingly strong E1 contributions below E_γ ≈ 17 MeV (1955GO59, 1964TO1A).

42. (a) ¹²C(γ, pα)⁷Li Q_m = -24.623
(b) ¹²C(γ, nα)⁷Be Q_m = -26.267

The yield of 0.48 MeV γ-rays from the decay of ⁷Be, formed in reaction (b), shows a resonance at E_γ ≈ 29.5 MeV, σ = 0.9 ± 0.2 mb. It is assumed to be the dipole state with a 5p - 5h character (J^π = 0⁺) based on ¹²C*(7.66) considered to be relatively pure 4p - 4h (1969OW01). For work on the γ-induced spallation of ¹²C see (1968TA10, 1969TA11). See also (1968DI1B, 1969DI18, 1971DI1F) and (1969ER1A; theor.). For older work on these reactions see (1968AJ02).

43. ¹²C(e, e)¹²C

The nuclear charge radius of ¹²C, R_rms = 2.462 ± 0.022 fm (1973FE13). Other values include R_rms = 2.445 ± 0.015 fm (Fermi model), 2.453 ± 0.008 fm (shell model) (1972JA10). See also (1969BE21, 1970BR1C, 1970SI08, 1971BE25, 1973EN1E, 1973KL12, 1973TH1B) and (1968AJ02). Elastic scattering has been studied up to 4 GeV: see (1968AJ02) for the earlier references and (1972JA10: E_e = 20 → 80 MeV), (1973KL12: E_e = 374.6 MeV), (1970SI08: E_e = 374.5 and 747.4 MeV) and (1971ST10: E_e = 1 to 4 GeV).

¹²C states observed in the inelastic scattering are displayed in Table 12.18 (in PDF or PS) (1963BO36, 1965BI1B, 1967CR01, 1968BE1H, 1968DO08, 1968ST20, 1969GU05, 1969TO01, 1970AN1C, 1970LI02, 1970ST10, 1970TO13, 1971BE51, 1971NA14, 1972SP1C, 1973CH16, 1974CE01). See also (1968PR01, 1969VA10). The variation of the form factor F(q²) with momentum transfer yields unambiguous assignments of J^π = 2⁺, 0⁺ and 3^-, respectively for ¹²C*(4.4, 7.7, 9.6) (1960BA38, 1964CR11, 1967HA1F). Form factors for ¹²C*(0, 4.4, 14.1) have been measured by (1971NA14). The isospin mixing between ¹²C*(12.71) and (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.

Inelastic scattering of the giant resonance has been studied by many groups: see (1968AJ02) for the earlier work and Table 12.18 (in PDF or PS). The longitudinal form factors show ¹²C*(16.1, 18.6, 20.0, 21.6, 22.0, 23.8, 25.5) while the transverse form factors show ¹²C*(15.1, 16.1, 16.6, 18.1, 19.3, 19.6, 20.6, 22.7, (25.5)) (1970AN1C, 1970TO13, 1971YA03, 1972AN03). See also (1969TO10). ¹²C*(19.3) may be the expected giant magnetic quadrupole state, J^π = 2^-: see (1968AJ02) and (1968BE1H, 1968DR01). See also (1970GR27; theor.).

(1974OB01) has measured the most probable energy loss for E_e = 50 and 100 MeV. See also (1968DE25, 1969CA1C, 1970AN1G, 1970DE04, 1971TI03, 1973ME1K), (1968GO1J, 1972THZF, 1973BI1A, 1973TH1B), reaction 44 and (1968AN1B, 1968BO1J, 1968CI1C, 1968FR1E, 1968HE1C, 1968HO1B, 1968KE10, 1968MA1N, 1968RA1B, 1969CH01, 1969CH1A, 1969CI1A, 1969DE14, 1969DO1D, 1969FU1F, 1969HE1F, 1969KA1H, 1969KU1C, 1969UB01, 1969VI02, 1970CH1H, 1970CH1J, 1970CI1B, 1970DO1F, 1970DO1G, 1970DO1H, 1970DO1A, 1970FR1E, 1970GO41, 1970GU12, 1970HI1C, 1970JA08, 1970LI18, 1970LI1P, 1970MC1D, 1970ON1B, 1970SA1B, 1970SP1C, 1971CI03, 1971DE1T, 1971DU06, 1971FR13, 1971MO1Q, 1971TA13, 1972AB19, 1972AN03, 1972AN15, 1972BE1X, 1972BO01, 1972EL11, 1972FR06, 1972GU25, 1972LE45, 1972OC01, 1972PA32, 1972ST35, 1972SU01, 1972UB01, 1973AL14, 1973BA05, 1973BO1Q, 1973DO1H, 1973FO1G, 1973FO1F, 1973GA19, 1973KU1N, 1973MA07, 1973MU04, 1973RI1A, 1973ROYN, 1973SI13, 1973SI1P, 1973SU03, 1973TA1F, 1974AB05, 1974BA1Z, 1974DZ06, 1974DZ05, 1974FR12, 1974IN05, 1974SI03; theor.).

44. (a) ¹²C(e, e'p)¹¹B Q_m = -15.9572
(b) ¹²C(e, e'n)¹¹C Q_m = -18.722
(c) ¹²C(e, e'α)⁸Be Q_m = -7.367
(d) ¹²C(e, eπ⁺)¹²B Q_m = -152.939
(e) ¹²C(e, eπ^-)¹²N Q_m = -156.913

Electron spectra in the region of large energy loss show a broad peak which is ascribed to quasi-elastic processes involving ejection of single nucleons from bound shells: see (1968AJ02). A study of e' - p coincidences for E_e = 550 - 600 MeV reveals peaks corresponding to ejection of 1p and 1s protons: the results are consistent with observations in (p, 2p) (1964AM1C, 1967AM03). At E_e = 497 MeV, the proton spectrum is dominated by an l = 1 transition to ¹¹B_g.s. (1974BE12). See also (1971BU26). The data obtained by (1974BE12) do not satisfy the sum rule of (1972KO01). The quasi-elastic scattering cross section has also been measured at E_e = 199.5 MeV (1969GU05), 500 MeV (1971MO06, 1974WH05) [the Fermi momentum is 221 ± 5 MeV/c (1971MO06)], 1 to 4 GeV (1971ST10) and 2.5 and 2.7 GeV (1974HE20, 1974KO21). See also (1967AM1A, 1968BO46, 1968DE25, 1969BE1L, 1969DE20, 1970DE04, 1970HI1F, 1970VY01, 1970WO1E, 1971EG03, 1971EG02, 1971SH09, 1972BE1U, 1972VL1A, 1973HE1H, 1974BA70, 1974SI1G) and (1967AM1C, 1972RA1E).

Absolute cross sections for reaction (b) have been measured for E_e = 20 to 30 MeV, using both electrons and positrons (1972KU27). See also (1973MO1G, 1973VO09). For reaction (c) see (1970EN1A). For reactions (d) and (e) see (1969TI04, 1970TI03, 1971TI03, 1971ST10, 1973HE1H) and the "Pion capture and pion reactions" section here. See also (1968BO1J, 1968BO1D, 1968CI1B, 1968DE1F, 1968MA1M, 1968WA1D, 1969DR05, 1969MO1G, 1969ST1E, 1969VY1A, 1969WA1E, 1970CI1C, 1970EP1A, 1970PA1H, 1970SI23, 1971BO1M, 1971CI1A, 1971PA42, 1971SH18, 1972AM1C, 1972AN03, 1972RA20, 1972RA18, 1972WE14, 1973BA2M, 1973BA71, 1973CI1A, 1973HI03, 1973JO1H, 1973SH02, 1974HA14, 1974KN1C, 1974ME24; theor.).

45. (a) ¹²C(π^-, π^-)¹²C
(b) ¹²C(π⁺, π⁺)¹²C
(c) ¹²C(π^-, π⁺π^-π^-)¹²C

Angular distributions of the elastic scattering and for the inelastic scattering to ¹²C*(4.4, 9.6, 15.0) have been measured at E_π^- = 120 to 280 MeV (1970BI1A). [Not all groups were measured at the seven energies in the above interval. ¹²C*(9.6) represents the group of levels with 9.6 ≤ E_x ≤ 10.8 and ¹²C*(15.0) those with 15.1 ≤ E_x ≤ 17.2 (1970BI1A).] Observation of 4.4 MeV γ-rays at E_π = 73 MeV leads to a cross section ratio (π^-/π⁺) of 1.23 ± 0.22. The cross section is 14.5 ± 3.0 mb for π⁺. The population of ¹²C*(15.11) was not observed in either reaction (1970HI10). The involvement of ¹²C*(4.4) in reaction (c) has been studied by (1973AS1A). See also the "GENERAL" section here, (1971TH05, 1975PI1E) and (1971RO14, 1974JA1F, 1974NI08; theor.).

46. (a) ¹²C(n, n)¹²C
(b) ¹²C(n, n')⁴He⁴He⁴He Q_m = -7.2748

Elastic and inelastic scattering to ¹²C*(4.4, 7.7, 9.6, 10.3, 10.8, 11.8) have been studied at many energies up to 350 MeV: see (1968AJ02) and Table 12.19 (in PDF or PS). Angular correlations of (n₁, γ_4.4) have been studied at E_n = 13.9 MeV (1973DE45) and 15.0 MeV (1971SP01), and at 14 - 14.7 MeV [see (1968AJ02)]. The spin-flip probability for the transition to ¹²C*(4.4) has been studied at E_n = 7.48 MeV (1971MC1K, 1972MC20) and at 15.0 and 16.9 MeV (1973TH08, 1974ME29). The shape of the angular distribution of the probability 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 is similar to that measured by (1969KO07) at E_p = 20 MeV (1974ME29).

At E_n = 14.4 MeV reaction (b) involves ¹²C*(9.6, 10.8, 11.8, 12.7). The decay of ¹²C*(11.8) leads to an assignment of J^π = 1^- (1964BR25, 1971DO1K, 1975AN01, 1975AN02). [See, however, Table 12.8 (in PDF or PS)]. See also (1966MO05, 1968BE1J).

See also ¹³C in (1976AJ04), (1968BR05, 1968KO1A, 1969PE1C, 1969RO1F, 1970BR1K, 1970MA1J, 1972DE31, 1974DR1C), (1968CA1A, 1968CH35, 1968TI1B, 1969AL1C, 1969DU1B, 1969OL03, 1970CA13, 1970SH14, 1971CH01, 1971MI07, 1972IK01, 1972JO11, 1972MO45, 1974CH1X; theor.) and (1969TR1A; astrophys. problems).

47. ¹²C(p, p)¹²C

Angular distributions of elastically and inelastically scattered protons have been measured at many energies up to E_p = 1040 MeV: see Table 12.22 (in PDF or PS) in (1968AJ02) for the earlier work and Table 12.20 (in PDF or PS) here. Angular distributions at E_p = 20 MeV (1963DI16, 1970BL03) and 46 MeV (1967PE05) show that a large quadrupole deformation exists: β₂ = -0.72 (1972DE13) and 0.6 (1967SA13), respectively.

Table 12.21 (in PDF or PS) shows the information on excited states of ¹²C. The angular distribution for ¹²C*(7.7) is best described by double quadrupole excitation via ¹²C*(4.4). ¹²C*(14.1) is identified as the 4⁺ rotational state (1967SA13). The values E_x = 7656.2 ± 2.1 keV (1971AU16), 7655.9 ± 2.5 keV (1971ST22) obtained for the 0⁺ second excited state of ¹²C lead to a substantial change in the reaction rate for helium-burning nucleosynthesis: see (1971AU16).

The in-plane and spin-flip pγ_4.4 angular correlations have been measured at 20 MeV. The substate cross sections were determined: these show a more pronounced structure than does the total inelastic cross section to ¹²C*(4.4). The M = 0 cross section is the most diffraction like. Agreement with the compound nucleus DWBA predictions is poor (1972TE01). The spin-flip probability in the scattering to ¹²C*(4.4) has been studied at E_p = 8.00 to 8.30 MeV (1972BE15), 12 to 14 MeV (1970KO15), 12, 13, 14, 15 and 20 MeV (1969KO07), 15.9 and 17.35 MeV (1971WI16) and 26.2 and 40 MeV (1969KO13). See also (1973SA1N). (1972BE15) find that the interference between the resonant and the background spin-flip is large: see ¹³N in (1976AJ04). At E_p = 26.2 and 40 MeV the observed spin-flip is almost entirely accounted for by distortions in the entrance and exit elastic channels, due to the spin-orbit term in the optical model potential (1969KO13).

For polarization measurements see (1970LI19, 1975GL1C) and ¹³N in (1976AJ04). See also (1971GA42, 1973TH1A, 1974AL1G, 1974BR1J, 1974DA1Q, 1974GA30, 1974OB1C, 1975PI1E), (1964KA1A, 1967LE13, 1968BA1K, 1968CH35, 1968GL1A, 1968KO26, 1968LE1D, 1968LI1B, 1968NE1B, 1968TA1D, 1968TA1E, 1968TI1B, 1969BA06, 1969BY1A, 1969HA07, 1969KO1H, 1969LE03, 1969MA1G, 1969NE1A, 1969OL03, 1969PE1E, 1969TA1D, 1969TI02, 1969WA11, 1970BA1F, 1970CA13, 1970CZ1A, 1970DA17, 1970GU15, 1970HA1J, 1970KO1L, 1970KR1E, 1970KU1C, 1970SA06, 1970SH01, 1970SH14, 1971AH03, 1971CH01, 1971FR1L, 1971HA31, 1971IN05, 1971JA16, 1971LE01, 1971MI07, 1971MO18, 1971RA36, 1971SH18, 1971SI11, 1971SI37, 1972AN12, 1972AU1A, 1972BA2E, 1972JO11, 1972IK01, 1972SI19, 1972SO03, 1972ST35, 1973AL14, 1973AU05, 1973DO10, 1973FR08, 1973GE1E, 1973KA04, 1973MA2B, 1973MI19, 1973SI37, 1973VA18, 1974AL1H, 1974BE22, 1974BR06, 1974IN04, 1974IN06, 1974IN07, 1974JA1F, 1974KU20, 1974SC1K, 1974ST02, 1973TE1B; theor.) and (1969TR1A; astrophys. questions).

48. (a) ¹²C(p, 2p)¹¹B Q_m = -15.9572
(b) ¹²C(p, pn)¹¹C Q_m = -18.722
(c) ¹²C(p, pd)¹⁰B Q_m = -25.1885
(d) ¹²C(p, pα)⁸Be Q_m = -7.367

At E_p = 56.5 MeV, ¹²C*(20.3 ± 0.5) is excited and then decays to ¹¹B_g.s. (1969EP01). At E_p = 385 MeV and estimate of the momentum distribution of the protons bound in ¹²C has been obtained. The results are consistent with a model in which the nuclear core is essentially a spectator. Distortion effects are mainly of an absorptive nature (1969JA05). At E_p = 1.0 GeV, the process is essentially quasifree (1970SI01, 1972CO11). See also (1971PA1H). Small angle multiple scattering of 600 MeV protons has been measured by (1972HU12). The angular correlation to ¹¹B(0) has been measured at E_p = 49.5 MeV by (1971HA61).

For reaction (b) see (1968PA05: E_p = 450 MeV). See also (1971TH05: p-bar, p-bar n), (1970TH1F) and (1972AB1G; theor.). For reaction (c) see (1970BA1T, 1971AZ01, 1972AZ03, 1972BO17, 1973KO1M) and (1968RO1F, 1974ZH01; theor.).

At E_p = 56.5 MeV, reaction (d) proceeds primarily by sequential α-decay: initially ¹²C*(19.7 ± 0.5, 21.1 ± 0.3, 22.2 ± 0.5 and 26.3 ± 0.5 MeV) are formed. The states, which therefore must have natural parity and a significant T = 0 admixture, subsequently decay to ⁸Be_g.s. [¹²C*(22.2, 26.0)] or ⁸Be*(2.9) [¹²C*(19.7, 21.1, 26.3)] (1969EP01). At E_p = 160 MeV, knock-out, sequential decay and spallation processes are observed (1970GO12). See also (1969HO1K, 1971GA1J, 1972MA62, 1972YA1B, 1973HO1R, 1973TH1A) and ⁸Be and ⁹B in (1974AJ01). For spallation studies see (1968KO1E, 1969DA1D, 1969ED01, 1969KO1G) and ¹³N in (1976AJ04). See also (1968ED1A). For pion production see (1970DO04), (1971IN1A, 1971RE12, 1972KE1F, 1973DI1G, 1974MI11; theor.), the "Pion capture and pion reactions" section here and ¹³C in (1976AJ04).

49. (a) ¹²C(d, d)¹²C
(b) ¹²C(d, pn)¹²C Q_m = -2.2246

The angular distribution of elastically and inelastically scattered deuterons has been studied at many energies to E_d = 650 MeV: see (1968AJ02) for the older references and Table 12.22 (in PDF or PS) here. DWBA analysis of the distributions at E_d = 80 MeV leads to β_l = 0.47 ± 0.05 and 0.35 ± 0.06 for ¹²C*(4.4, 9.6), respectively (1971DU09). E_x of ¹²C*(4.4) is 4440.5 ± 1.1 keV: the average of this value and of the one determined in (p, p') (Table 12.21 (in PDF or PS)) gives 4439.5 ± 1.0 keV (1974JO14). The isospin mixing of ¹²C*(12.71, 15.11) [both J^π = 1⁺; T = 0 and 1, respectively] has been measured for E_d = 27.2 and 28.0 MeV. The ratio of the cross sections for the population of the T = 1 and 0 states is (7.0 ± 1.2) x 10^-3. [In a remeasurement of this quantity (1975LI1K) find ≈ (1.1 × 10^-2). Angular distributions for the two states were obtained at E_d = 24.1, 26.2, 27.5 and 28.8 MeV (1975LI1K).] This leads to β² = 0.011 ± 0.003 (1972BR27: see also reactions 66, 67, 76). For a study of the distribution of ionic charge when ¹²C recoils in elastic scattering at E_p = 10 MeV, see (1971WO10).

Reaction (b) has been studied, in a kinematically complete experiment, at E_d = 5.00 to 5.50, 9.20 and 9.85 MeV by (1970SA1K, 1973SA03). An increase in yield is observed for all spectra in the region of low relative proton-neutron energy where both rescattering and sequential decay leading to the ¹S₀ final state interaction are possible. Due to the probable superposition and interference of different reaction mechanisms, it is apparently not possible to evaluate how much spin singlet and spin triplet interaction is involved (1973SA03). See, however, (1973SH04). Studies of reaction (b) are also reported at E_d = 5.1 to 6.25 MeV (1973SH04), 5.4 and 6.0 MeV (1968BO02) and 5.5 to 6.5 MeV (1970VA1K, 1972VA10). See also ¹³C and ¹³N in (1976AJ04) and (1972GE1G).

50. ¹²C(t, t)¹²C

Angular distributions of elastically scattered tritons have been determined at E_t = 1.0 to 1.75 MeV (1962GU01, 1969HE08), 1.11 to 3.40 MeV (1969ET01 and private communication), 1.75 and 2.10 MeV (1969SI12), 6.4, 6.8 and 7.2 MeV (1964PU01), 12 MeV (1965GL04, 1966GL1B), 16 and 20 MeV (1972KE02) and 20.04 MeV (1974JA25). See also (1968HO1C) and (1971KA04; theor.).

51. ¹²C(³He, ³He)¹²C

Angular distributions of ³He ions have been measured at many energies in the range E(³He) = 2 to 217 MeV: see reaction 43 in (1968AJ02) for the older measurements and Table 12.22 (in PDF or PS), here, for the newer ones. DWBA analyses seem to be inadequate: complete coupled channels analyses appear to be necessary to explain the data; see, e.g., (1972AS03, 1973SI11).

Angular distributions of the ³He groups to ¹²C*(15.11, 16.11, 16.58, 19.57) have been compared with those for the tritons to ¹²N*(0, 0.96, 1.19, 4.25) in the analogue reaction ¹²C(³He, t)¹²N: the correspondence is excellent and suggests strongly that these are T = 1 isobaric analogue states (1968BA1E, 1969BA06: E(³He) = 49.8 MeV). See also Tables 12.13 (in PDF or PS) and 12.23 (in PDF or PS), ¹²N and (1970AR05, 1974WI16). The (³He', γ₁) reaction plane angular correlation has been measured at E(³He) = 17 MeV as a function of gamma-ray angle for 43 ³He scattering angles. The spin-flip probability was also determined, and the quadrupole deformation was found to be β₂ = -0.60 (1968AS03, 1972AS03). See also (1971PA1K, 1974YA10). For polarization measurements see ¹⁵O in (1976AJ04).

See also (1967AR17, 1967BA1D, 1970JA1E, 1970KA1D) and (1968LE1G, 1968PA1F, 1969RA1B, 1970CA1G, 1973BR1L; theor.).

52. (a) ¹²C(α, α)¹²C
(b) ¹²C(α, 2α)⁸Be Q_m = -7.367

Angular distributions have been measured at many energies to E_α = 166 MeV: see Table 12.24 (in PDF or PS) in (1968AJ02) and Table 12.22 (in PDF or PS) here. Alpha-particle groups have been observed to many ¹²C states: see Tables 12.22 (in PDF or PS) and 12.23 (in PDF or PS) (1972FA07). J^π assignments have also been suggested for ¹²C states with 9.6 ≤ E_x ≤ 39.3 MeV on the basis of their decay into 3 α-particles: see (1973JA02; E_α = 90 MeV). See also (1969BA06).

Angular correlation measurements (α₁γ_4.4) have been carried out at E_α = 10.2 to 10.5 MeV (1972KE18), 18.0 to 24.0 MeV (1968KL07), 19 MeV (1972AS03), 19.3 to 25.3 MeV (1972EL09), 22.75 MeV (1970HA15), 32.5 MeV (1972BU09) and 41 MeV (1971BA64): the relative population of magnetic substates has been studied by (1970HA15, 1972BU09). See also (1968AJ02). The quadrupole deformation, β₂, is -0.29 ± 0.02 (1971SP08), 0.46 (1973SM03); β₃ = 0.24 (1973SM03). See also (1971BE60, 1972EE1A).

Measurements of the radiative widths yield Γ_rad/Γ = (4.2 ± 0.2) × 10^-4 [Γ_rad ≡ Γ_γ + Γ_e^± is then 3.7 ± 1.2 meV] for ¹²C*(7.7) (1974CH03) and Γ_rad/Γ < 4.1 × 10^-7 [Γ_rad < 14 meV] for ¹²C*(9.6) (1974CH32): see also Table 12.9 (in PDF or PS). The value for Γ_rad for ¹²C*(7.7) implies a 45% faster rate for the (ααα) astrophysical process (1974CH03). See also (1973HA1Y, 1974MA2C). For total cross sections for formation of various ¹²C states, see ¹⁶O in (1971AJ02, 1977AJ02) and (1973SP1D).

For polarization measurements, see ¹⁶O in (1977AJ02). See also (1967HA1G, 1968CA11, 1968ED1B, 1968GA1D, 1968RA1C, 1968SH1D, 1968SH1E, 1968TO1D, 1969BU1D, 1969PI02, 1971MU1H, 1971TA30, 1971TE10, 1972DM01, 1973AL14, 1973BR1K, 1973BU1G, 1973DM01, 1973KU08, 1973SI1M, 1974PI11, 1974GO1U, 1974HO19, 1974WA02; theor.) and (1969TR1A; astrophys. questions).

Reaction (b) at E_α = 25 MeV appears to involve ¹²C*(7.66, 9.64) (1969DO02, 1969DO03). See also (1974RU06). See (1968YA02, 1969PI1B, 1970KE1B, 1970EI05, 1970PI1D, 1973RU09, 1974DO1G) for other studies of the (α, 2α) reaction with E_α up to 700 MeV. See also ⁸Be in (1974AJ01), (1971GA1J) and (1968BA1H, 1970BU1C, 1970MI12, 1972AV04, 1972MI05; theor.).

53. (a) ¹²C(⁶Li, ⁶Li)¹²C
(b) ¹²C(⁷Li, ⁷Li)¹²C

The elastic scattering in reaction (a) has been studied at E(⁶Li) = 4.5 to 13 MeV (1972PO07), 20 MeV (1968BE1K, 1972WA31), 24.5 MeV (1968DA20), 28 MeV (1972BA52), 30 MeV (1971CH1P, 1971DA33), 34 and 36 MeV (1973SC26; also ¹²C*(4.4)) and 36.4 and 40 MeV (1974BI04). See also (1964OL1A). (1974BI04) have also measured the inelastic angular distributions to ¹²C*(4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 13.4, 14.1) and have calculated deformation parameters under various assumptions. Two step processes are important in the excitation of ¹²C*(7.7, 14.1) (1974BI1H). See also (1971DA1J) and (1968NO1C, 1971OS02, 1974AS1D; theor.).

The elastic scattering in reaction (b) has been studied at E(⁷Li) = 4.5, 5.8, 9.0, 11.0 and 13.0 MeV (1972PO07), 15 and 21.1 MeV (1972WE08) and at 36 MeV (1973SC26). At 36 MeV the angular distributions corresponding to ¹²C_g.s. + ⁷Li^*_0.48, ¹²C^*_4.4 + ⁷Li_g.s. and ¹²C^*_4.4 + ⁷Li^*_0.48 have also been studied (1973SC26).

54. ¹²C(⁹Be, ⁹Be)¹²C

Elastic scattering angular distributions have been obtained at E(¹²C) = 12, 15, 18 and 21 MeV (1970BA49).

55. (a) ¹²C(¹⁰B, ¹⁰B)¹²C
(b) ¹²C(¹¹B, ¹¹B)¹²C

Angular distributions have been measured for reaction (a) at E(¹⁰B) = 18 MeV (1968VO1A, 1969VO10: to g.s.) and 100 MeV (1973BI1J, 1974BI1E: to ¹²C*(0, 4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 13.4, 14.1, 14.8). Two-step processes appear to be involved in the excitation of ¹²C*(7.7, 14.1) (1974BI1E). See also (1974AS1D; theor.).

Angular distributions for reaction (b) have been studied at E(¹²C) = 15, 17, 20 and 24 MeV (1974BO15: to g.s.) and 87 MeV (1971LI11: to g.s.), and at E(¹¹B) = 28 MeV (1968VO1A, 1969VO07, 1969VO10: to g.s., 4.4; and to several ¹¹B states). A consistent description of the elastic data at E(¹²C) = 15 to 24 MeV is obtained by including the elastic transfer of a 1p_1/2 hole (1974BO15). See also (1972SC1Q) and (1970AN1D, 1973DE35; theor.).

For yield measurements see ²²Na and ²³Na in (1973ENVA) and (1974DA1P).

56. ¹²C(¹²C, ¹²C)¹²C

Angular distributions have been measured at E(¹²C) = 18.8 to 37.6 MeV (1973EM03: g.s. + g.s., g.s. + 4.4, 4.4 + 4.4), 40 to 60 MeV (1973WI09: g.s. + g.s., g.s. + 4.4, 4.4 + 4.4), 70 MeV (1971KO11: g.s.) and at 87 MeV (1971LI11: g.s.). At E(¹²C) = 114 and 174 MeV differential cross sections have been measured for the population of ¹²C*(0, 4.4, 7.7, 9.6, 14.1, 19.6). The population of ¹²C^*_4.4 + ¹²C^*_4.4 is also reported (1973AN22).

The relative population of elastic and inelastic channels is very energy dependent: see ²⁴Mg in (1973ENVA) and (1968WI1C, 1973EM03, 1973GO01, 1973RE13, 1973RE12, 1973WI09, 1974RA1J, 1974RA1K, 1974SH16, 1974SP06, 1974VO09, 1975OB1B).

57. (a) ¹²C(¹³C, ¹³C)¹²C
(b) ¹²C(¹⁴C, ¹⁴C)¹²C

Elastic angular distributions in reaction (a) have been studied at E(¹²C) = 15 and 19 MeV (1971BO52, 1971BO1U, 1972BO68), at 20 to 36 MeV (1972CH1H, 1973CH1L; and also to ¹²C*(4.4) and various states in ¹³C) and at 87 MeV (1971LI11). See also (1970GO1B, 1971WI1J, 1973BR1C, 1973GO01, 1973SC1B) and ¹³C in (1976AJ04). Elastic angular distributions in reaction (b) are reported at E(¹²C) = 12 to 20 MeV (1972BO68).

For yield measurements, see (1972BO68, 1973FE03, 1974CR03) and ²⁴Mg and ²⁵Mg in (1973ENVA). See also (1970VO1D, 1973BA2K, 1973DE35, 1973MC1J, 1973SA1K, 1973VO04, 1974GA1L, 1974IM1B; theor.).

58. ¹²C(¹⁴N, ¹⁴N)¹²C

Angular distributions have been measured at E(¹⁴N) = 21 MeV (1971BO1U, 1971VO01: to g.s.), 22.5 MeV (1969HE06: to g.s.), 65, 84 and 88 MeV (1971KO11: to g.s.), 78 MeV (1970VO02: to g.s., 4.4) and 155 MeV (1974BI1E: to g.s., 4.4, 7.7, 9.6, 10.8, 11.8, 12.7, 13.4, 14.1; see also reaction 54). See (1968AJ02) for earlier measurements. See also ¹⁴N in (1976AJ04), (1974AN36) and (1974NA1G). For yield measurements see ²⁶Al in (1973ENVA) and (1974JO1J, 1974ST1N). See also (1969BR1D) and (1972MA74, 1974GA1L; theor.).

59. (a) ¹²C(¹⁶O, ¹⁶O)¹²C
(b) ¹²C(¹⁶O, α)¹²C¹²C Q_m = -7.1616

Elastic angular distributions have been measured at E(¹⁶O) = 20, 24, 35 and 42 MeV (1968VO1A, 1969VO10), 26, 30 and 32.5 MeV (1969KR03), 27 to 53 MeV (1972MA29, 1972MA1P), 36 MeV (1971OR02) and 65 and 80 MeV (1973GU12). At E(¹⁶O) = 65 and 80 MeV, angular distributions involving ¹²C*(0, 4.4) and various states of ¹⁶O have been studied by (1973GU12): see ¹⁶O in (1977AJ02).

A kinematically complete study of reaction (b) has been carried out at E(¹⁶O) = 58.3 MeV. The main process appears to involve (¹²C + α) corresponding to an excited state of ¹⁶O with E_x ≈ 10 MeV. Formation and decay of compound states in ²⁴Mg are also involved (1974WI05). See also (1973ENVA).

For studies of the yields of these reactions see (1968MA1J, 1969VO10, 1972MA29, 1972ST09, 1973CH1N, 1973MA1N, 1974MA1L, 1974WI05). See also ²⁸Si in (1973ENVA).

60. (a) ¹²C(¹⁷O, ¹⁷O)¹²C
(b) ¹²C(¹⁸O, ¹⁸O)¹²C

The elastic scattering angular distributions in both (a) and (b) have been measured at E = 35 MeV (1967GO1A). See also ¹⁸O in (1978AJ03) and (1971BE60, 1974CH1Q).

61. ¹²C(¹⁹F, ¹⁹F)¹²C

Elastic scattering angular distributions have been measured at E(¹⁹F) = 40, 60 and 68.8 MeV (1968VO1A, 1969VO10, 1972SC03). See also (1970AN1D, 1970BL1E; theor.).

62. ¹²C(²⁰Ne, ²⁰Ne)¹²C

The elastic scattering angular distribution has been measured at E(¹²C) = 37 MeV (1974VA18). See also ³²S in (1973ENVA).

63. ¹²N(β⁺)¹²C Q_m = 17.344

The decay is mainly to the ground state via an allowed transition. Branching ratios to other states of ¹²C are displayed in Table 12.24 (in PDF or PS). The half-life is 10.97 ± 0.04 msec: see Table 12.28 (in PDF or PS) in (1968AJ02). Since transitions to ¹²C*(g.s., 4.4) are allowed J^π(¹²N) = 1⁺.

Recent measurements of the ratios of the branching ratios, ¹²N/¹²B, for the decays to ¹²C*(4.4) is 1.52 ± 0.06 (1972AL31), 1.74 ± 0.08 (1974MC11). Using R = 1.63 ± 0.11, and other data, (1974MC11) find that the asymmetry in the decay to the excited state is δ_4.44 = -0.013 ± 0.066 and that δ_g.s. = 0.1155 ± 0.0085. See also (1973KU1D; theor.).

¹²C*(12.7), populated in an allowed transition, decays primarily to ⁸Be*(2.9) [J^π = 2⁺]; the absence of decay to ⁸Be_g.s. is in agreement with the assignment J^π = 1⁺ (1966SC23). The ft values for the β-transitions to ¹²C*(12.7, 15.1) agree well with shell-model calculations of (1965CO25). The agreement strongly suggests a close relation between ¹²C*(12.7) [J^π = 1⁺; T = 0] and ¹²C*(15.1) [J^π = 1⁺; T = 1]. See also (1971MI06, 1973CH16, 1973MIYZ).

64. ¹³C(γ, n)¹²C Q_m = -4.9464

At E_bs = 28 MeV, 4.4 and 15.1 MeV γ-rays have been observed corresponding to the population of ¹²C*(4.4, 15.1), while at E_bs = 21 MeV only ¹²C*(4.4) is excited (1971MU11). See also (1971WI1N), (1973KI1J; theor.) and ¹³C in (1976AJ04).

65. (a) ¹³C(p, d)¹²C Q_m = -2.7218
(b) ¹³C(p, pn)¹²C Q_m = -4.9464

Angular distributions of the d₀ and d₁ groups to ¹²C*(0, 4.4) have been measured at E_p = 8 and 12 MeV (1966GL01), 17 MeV (1961BE12), 50 MeV (1970SC02) and 54.9 MeV (1968TA08). In addition angular distributions have also been measured for the groups to ¹²C*(12.7, 15.1, 16.1) at the two higher energies (1968TA08, 1970SC02). ¹²C*(14.1) is not excited, consistent with J^π = 4⁺ (1970SC02, 1974PA01). At E_p = 62 MeV, (1974PA01) report the excitation of states with E_x = 15112 ± 5, 16110 ± 5 [< 20], 17760 ± 20 [80 ± 20], 18800 ± 40 [80 ± 30], 21500 ± 100 [< 200] and 22550 ± 50 [< 200] keV [the numbers shown in the brackets are Γ_c.m., in keV]: l_n = 1 for all states except ¹²C*(21.5) and (22.55) for which l_p = (1) and ≠ 1, respectively. Spectroscopic factors are derived by (1968TA08, 1970SC02, 1974PA01). At E_p = 17 MeV (1969CO06) give the ratio of σ(p, d)/σ(p, d-bar) to the ground state of ¹²C as 17. (1971OT02) suggest, however, that a part of the apparent (p, d-bar) cross section may be due to ¹²C + n final state interaction through ¹³C*(10.75). In a kinematically complete experiment at E_p = 7.9 to 12.5 MeV, it is found that sequential decay via states in ¹³C and ¹³N is strongly involved in reaction (b). Near E_p = 12.5 MeV there is some indication of sequential decay via singlet deuteron formation (1971OT02). See also (1967SP09, 1970VA1K) and ¹³C, ¹³N and ¹⁴N in (1976AJ04).

66. ¹³C(d, t)¹²C Q_m = 1.3112

Angular distributions have been obtained at E_d = 0.41 to 0.81 MeV (1971PU01: t₀), 1.0 to 2.7 MeV (1970LI1E, 1971LI1K: t₀), 2.2 and 3.3 MeV (1954HO48: t₀), 8 and 12 MeV (1966GL01: t₀, t₁), 12.1, 13.3 and 14.0 MeV (1968TE04: t₀, t₁), 13.6 MeV (1973ZA06: t₀, t₁), 14.8 MeV (1960MA10: t₀, t₁, t₂), 15 MeV (1974LU06) and 28 MeV (1972BR27). In the latter experiment (1972BR27) have studied the triton groups to ¹²C*(12.7, 15.1, 16.1) [J^π; T = (1⁺; 0), (1⁺; 1) and (2⁺; 1), respectively] and the ³He groups, in the analogue reaction, to ¹²B*(0, 0.95) [J^π = 1⁺; T = 1 and J^π = 2⁺; T = 1, respectively]. The relative yield to ¹²C*(15.1) is greater than that to its analogue, ¹²B_g.s., while the yields to the 2⁺ states are in good agreement. The value of β required to give the observed ratio of yields for the 1⁺ states is 0.13 [in good agreement with the (d, d') results: see reaction 49]: the charge-dependent matrix element is then 250 ± 50 keV (1972BR27). See also ¹⁵N in (1976AJ04), (1967SP09, 1969DE1H) and (1969LI1D; theor.).

67. (a) ¹³C(³He, α)¹²C Q_m = 15.6321
(b) ¹³C(³He, 2α)⁸Be Q_m = 8.2653

Angular distributions have been measured at many energies up to E(³He) = 45 MeV: see (1968AJ02) for the earlier references and (1971BO26: 1.5 to 5.3 MeV; α₀, α₁, α₂) and (1968AR12: 19.1, 27.3, 35.7, 36.8 MeV; α₀, α₁, α₂, α₃ and α to ¹²C*(12.7, 15.1, 16.1)). Angular correlations of α-particles and 4.4 MeV γ-rays have been studied at E(³He) = 4.5 MeV (1962HO13) and for αγ_15.1 at 9.4 and 11.2 MeV (1969TA09). See also (1975MA2J).

Attempts have been made using this reaction (1970AR30, 1970RE09, 1974BA42) and reactions 49 and 66 to study the T mixing between the 1⁺ states ¹²C*(12.71, 15.11). Reported values for Γ_α/Γ for ¹²C*(15.11) are 1.2 ± 0.7% (1970RE09, 1970RE1F), 6.0 ± 2.5% (1970AR30), 4.1 ± 0.9% (1974BA42). The (1974BA42) value was obtained by observing the decay α-particles in reaction (b): adopting this value, and using the other parameters for the decay of ¹²C*(15.11) [see Table 12.9 (in PDF or PS)] leads to Γ_α = 1.8 ± 0.3 eV. If this isospin forbidden α-width is the result of mixing between the two 1⁺ states via a charge-dependent interaction, the matrix element is 340 ± 60 keV (1974BA42). (1970RE09) have measured branching ratios for the decays of ¹²C*(12.7, 15.1): see Table 12.9 (in PDF or PS). See also ¹⁶O in (1977AJ02).

68. (a) ¹³C(⁶Li, ⁷Li)¹²C Q_m = 2.3042
(b) ¹³C(⁷Li, ⁸Li)¹²C Q_m = -2.9136

At E(⁷Li) = 34 MeV angular distributions have been observed for the reactions to ¹²C*(0, 4.4) + ⁷Li*(g.s., 0.48) and ⁸Li*(0, 0.95) in all combinations. While ¹²C*(0, 4.4) are dominant in the two spectra, ¹²C*(7.7, 9.6) and, in reaction (a) at E(⁶Li) = 36 MeV, ¹²C*(12.7) are also populated (1973SC26).

69. (a) ¹³C(¹⁶O, ¹⁷O)¹²C Q_m = -0.8040
(b) ¹³C(¹⁷O, ¹⁸O)¹²C Q_m = 3.1004
(c) ¹³C(¹⁸O, ¹⁹O)¹²C Q_m = -0.9895

Angular distributions have been obtained for reaction (a) at E(¹⁶O) = 14, 17 and 20 MeV (1968KN1A, 1971BA68: ¹²C_g.s + ¹⁷O*(g.s., 0.87)), 41.7 and 46.0 MeV (1973DE21). See also ²⁸Si in (1973ENVA) and (1974BE1J; theor.).

For reaction (b) see (1974CH1Q). Ground state angular distributions for reaction (c) have been measured at E(¹⁸O) = 15, 20 and 24 MeV (1971BA68, 1971KN05). See also (1974CH1Q).

70. ¹⁴C(p, t)¹²C Q_m = -4.6412

Angular distributions have been measured at E_p = 14.5 MeV (1971CU01: t₀), 18.5 MeV (1963LE03: t₀) and 39.8 MeV (1970OL1B, 1973HO10: t₀, t₁). At E_p = 50.5 MeV the excitation of a T = 2 state with E_x = 27.595 ± 0.020 MeV is reported by (1970NE1A, 1971NE1B, 1971NE1E; unpublished results). This state has also been observed at E_p = 54 MeV as has another narrow state at E_x = 29.6 ± 0.1 MeV. The angular distribution of the tritons to the lower state is consistent with L = 0; that for the higher state is rather featureless (D. Ashery, private communication). [See also reaction 24 in ¹²B.] See also (1971KA04; theor.).

71. (a) ¹⁴C(¹⁶O, ¹⁸O)¹²C Q_m = -0.9342
(b) ¹⁴C(¹⁸O, ²⁰O)¹²C Q_m = -1.563

Angular distributions leading to the ground states in reaction (a) have been measured at E(¹⁶O) = 20, 25 and 30 MeV (1973SC24). For reaction (b) see (1972EY01) and ²⁰O in (1978AJ03).

72. ¹⁴N(γ, np)¹²C Q_m = -12.4971

See (1970TH01, 1972GE11), ¹³C and ¹⁴N in (1976AJ04), and (1973KI05; theor.).

73. ¹⁴N(n, t)¹²C Q_m = -4.0149

Angular distributions of the t₀ group have been measured at E_n = 14 - 15 MeV: see (1968AJ02). The γ-ray from ¹²C*(4.4) has been seen: E_γ = 4436 ± 5 keV (1971NY03). See also ¹⁵N in (1976AJ04) and (1971MI1H).

74. ¹⁴N(p, pd)¹²C Q_m = -10.2725

At E_p = 46 MeV the transitions to ¹²C*(0, 4.4) have been studied by (1970WE1J, 1971WE05). See also ¹⁴N in (1976AJ04).

75. ¹⁴N(p, ³He)¹²C Q_m = -4.7787

Angular distributions have been studied at E_p = 7.53, 8.03, 9.54 and 10.54 MeV (1970ME30: g.s.), 20.5, 24.3, 29.4, 34.6, 40.1 and 44.6 MeV (1974PI05: g.s., 4.4), 39.8 MeV (1973HO10: g.s., 4.4) and 50 MeV (1970SC02: g.s., 4.4, 12.7, 14.1, 15.1, 16.1). The results of (1970SC02) strongly indicate J^π = 4⁺ for ¹²C*(14.1). See also ¹⁵O in (1970AJ04, 1976AJ04), (1968SH11, 1968TO1E) and (1970CH1E; theor.).

76. (a) ¹⁴N(d, α)¹²C Q_m = 13.5751
(b) ¹⁴N(d, 2α)⁸Be Q_m = 6.2084

Observed α-particle groups are shown in Table 12.23 (in PDF or PS) (1956DO41, 1965PE17, 1965SC12, 1972FA07). Angular distributions have been measured at many energies up to E_d = 28.5 MeV: see (1968AJ02) for the earlier work and (1969GO14: 1.0 - 3.1 MeV; α₀ → α₃), (1971AR41: 1.70, 2.30, 2.90 MeV; α₀, α₁, α₂), (1967BO37: 2.29 - 5.76 MeV; α₀, α₁), (1969CU08: 10.5 MeV; α₀ → α₃), (1970SC02: 15 to 20 MeV; α₀, α₁ and α to ¹²C*(12.7, 14.1)), (1968SC1C: 17 MeV; α₁ → α₃ and α to ¹²C*(12.7, 14.1)), (1968MA1K: 20 MeV; α₀ → α₃ and α to ¹²C*(12.7, 14.1)) and (1967VI03: 28.5 MeV; α₀, α₁. At E_d = 40 MeV the upper limits for the ratio of the cross sections to ¹²C*(15.11) and ¹²C*(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 (1972BR27): see reactions 49, 66 and 67. For reaction (b) see (1972FA07). See also ¹⁶O in (1977AJ02), (1967SP09) and (1968DA1K, 1968ZE1B, 1969JO23, 1970JA1J; theor.).

77. ¹⁴N(³He, pα)¹²C Q_m = 8.0814

See (1969HO13), ¹³N in (1970AJ04, 1976AJ04) and ¹⁶O in (1971AJ02, 1977AJ02).

78. (a) ¹⁴N(α, ⁶Li)¹²C Q_m = -8.7987
(b) ¹⁴N(α, αd)¹²C Q_m = -10.2725

At E_α = 42 MeV, angular distributions of ⁶Li ions corresponding to transitions to ¹²C*(0, 4.4) have been measured by (1964ZA1A). Reaction (b) at E_α = 22.9 MeV proceeds by sequential decay via states in ¹⁴N, ¹⁶O or ⁶Li to ¹²C_g.s. (1969BA17): see also ⁶Li in (1974AJ01), ¹⁴N in (1970AJ04) and ¹⁶O in (1971AJ02).

79. (a) ¹⁴N(¹⁰B, 3α)¹²C Q_m = 7.6413
(b) ¹⁴N(¹⁰B, ¹²C)¹²C Q_m = 14.9161

See (1965SH1A) (reaction (a)) and (1973ST1A) (reaction (b)).

80. ¹⁵N(p, α)¹²C Q_m = 4.9661

Angular distributions of α₀ and α₁ have been measured for E_p up to 18.6 MeV (see (1968AJ02)) and at six energies in the range E_p = 19.85 to 43.35 MeV (1971GU23). At E_p = 43.7 MeV the angular distributions to the 0⁺ states ¹²C*(0, 7.66, 17.76) are fitted by L = 1, and L = 3 is consistent with the distributions to ¹²C*(14.1, 16.1) [J^π = 4⁺ and 2⁺, respectively] (1972MA21). The lifetime of ¹²C*(4.4) τ_m = 65 ± 9 fsec (1970CO09). The energy of the second excited state of ¹²C is 7654.2 ± 1.6 keV. The weighted average of this and previous values leads to E_x = 7654.6 ± 1.1 keV, a value which leads to a sharply reduced rate for the (ααα) process (1973MC01). See also (1972CA1N, 1973CL1E; astrophys. questions) and (1967SP09).

81. ¹⁵N(α, ⁷Li)¹²C Q_m = -12.382

At E_α = 42 MeV angular distributions have been obtained for all four of the transitions ¹²C_g.s. + ⁷Li*(g.s., 0.48) and ¹²C^*_4.4 + ⁷Li*(g.s., 0.48) (1968MI05).

82. (a) ¹⁶O(γ, α)¹²C Q_m = -7.1616
(b) ¹⁶O(γ, 3α)⁴He Q_m = -14.4364

There is evidence for the involvement of many ¹²C states: see (1965RO05, 1967CA1C). See also (1973CL1E; astrophys. questions).

83. (a) ¹⁶O(n, nα)¹²C Q_m = -7.1616
(b) ¹⁶O(p, pα)¹²C Q_m = -7.1616

For reaction (a) see (1968AJ02). Reaction (b) appears to proceed primarily via excited states of ¹³N and ¹⁶O to ¹²C*(0, 4.4): see (1971EP03: E_p = 46.8 MeV) and (1972BO71: E_p = 50 MeV), ¹³N in (1976AJ04) and ¹⁶O in (1971AJ02, 1977AJ02). At E_p = 160 MeV, unpublished measurements by S.L. Kannenberg quoted by (1971EP03) show that reaction (b) proceeds in part by quasi-elastic scattering to ¹²C_g.s.. See also (1970GO12).

84. ¹⁶O(d, ⁶Li)¹²C Q_m = -5.6879

Angular distributions have been determined at E_d = 13.6 and 14.6 MeV (1974GA30: g.s.), 14.6 MeV (1964DA1B: g.s.), 19.5 MeV (1971GU07: g.s., 4.4), 28 MeV (1972BE29, 1972BE1T: g.s., 4.4), 35 MeV (1975BE01: g.s.) and 55 MeV (1971MC04: g.s., 4.4, 7.7, 9.6, 14.1). See also (1969KE1C, 1972CO23), (1967OG1A, 1972GA1E) and (1971DR02, 1972RO1L, 1974DO03, 1974KU05; theor.).

85. ¹⁶O(³He, ⁷Be)¹²C Q_m = -5.575

Angular distributions have been measured at E(³He) = 25.5 to 29 MeV (1972PI1A: ¹²C*(0, 4.4) + ⁷Be*(0, 0.4)) and 30 MeV (1970DE12: ¹²C*(0, 4.4, 9.6) + ⁷Be*(0, 0.4), ¹²C*(7.6) + ⁷Be(0)). See also (1971DE37, 1973PI1B, 1973ST1N) and (1972RO1L, 1973KL1B; theor.). (1975AU01) report the extraction of the α-particle pickup spectroscopic factor S_α using a finite range DWBA analysis (E(³He) = 26 MeV).

86. (a) ¹⁶O(α, 2α)¹²C Q_m = -7.1616
(b) ¹⁶O(α, ⁸Be)¹²C Q_m = -7.2535

Reaction (a) at E_α = 25 MeV proceeds in part by sequential decay via states in ¹⁶O and ²⁰Ne (1968PA12): see (1971AJ02, 1972AJ02). See also (1971BR1G, 1972SH1J). Angular distributions for the transitions to ¹²C*(0, 4.4) in reaction (b) have been studied at E_α = 35.5 to 41.9 MeV (1965BR13) and 65 MeV (1973WO06). The excitation of ¹²C*(9.6, 14.1) is also reported (1973WO06, 1974WO1D). See also (1972SH10; theor.) and (1973SC1B).

87. ¹⁶O(¹⁴N, ¹⁸F)¹²C Q_m = -2.746

See (1966GA10). See also (1969BR1D) and (1970AN1D; theor.).

88. ¹⁶O(¹⁶O, ²⁰Ne)¹²C Q_m = -2.432

Angular distributions have been measured at E(¹⁶O) = 23.9 MeV (1974SP06: g.s. + g.s.) and 51.5 MeV (1974RO04: ¹²C*(0, 4.4) and various ²⁰Ne states). See also (1971SI1F, 1973PE1D, 1974ER1A), ²⁰Ne in (1978AJ03) and ³²S in (1973ENVA).