A=14C (1981AJ01)

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¹⁴C (1981AJ01)

(See Energy Level Diagrams for ¹⁴C)

GENERAL: See also (1976AJ04) and Table 14.3 [Table of Energy Levels] (in PDF or PS).

Nuclear models: (1976VO1C).

Special levels: (1978AL1T, 1979HOZW).

Special reactions involving ¹⁴C: (1976AB04, 1976BU16, 1976LE1F, 1977AR06, 1978AB08, 1978GE1C, 1978HE1C, 1978KA23, 1978KO01, 1978LE15, 1978TU06, 1979AL22, 1979BO22).

Giant resonance: (1979DO17, 1979KI11).

Astrophysical questions: (1976DE1G, 1976LI1K, 1977BR1N, 1977CO1U, 1977HA1L, 1977KU1J, 1978BU1B, 1979DE1V, 1979OL1B, 1980ST1C).

Muon and neutrino capture and reactions: (1977GO13, 1978DE15, 1979GO1M, 1980LO07, 1980MU1B).

Pion and kaon capture and reactions (See also reactions 19, 36 and 44.): (1976DI11, 1976DI10, 1976EN02, FI76F, 1977DO06, 1977RI1H, 1978DA1A, 1978SH16, 1979KI11, 1980ER01, 1980FI05).

Applied work: (1976LI1K, 1977ME1D, 1977MU1B, 1977RY1A, 1978AI1A, 1978BE2D, 1978DO1G, 1978HE1M, 1978MU1E, 1979BE2J, 1979GO1L, 1979LI1C, 1979MU1E, 1979ST1P, 1979TA1N, 1980GO1B).

Other topics: (1976ST13, 1978DA1A, 1978GA1C, 1978PO1A, 1978SO1A, 1979KA13).

Ground state of ¹⁴C: (1976BE1G, 1977AN21, 1978AN07, 1978HE1D, 1978NA07, 1978SM02, 1978TA09).

1. ¹⁴C(β^-)¹⁴N Q_m = 0.1565

The adopted value of the half-life is 5730 ± 40 y: see (1976AJ04). Using Q_m, log ft = 9.04 (1971GO40). For discussions of the lifetime of ¹⁴C see (1959AJ76, 1970AJ04, 1976AJ04). See also (1978MA1P), (1976BE1E), (1980RO1D; applied) and (1977GO13, 1977IK1B, 1977RI08, 1979DE15, 1979FE1E, 1979PR1D, 1980LO07; theor.).

2. (a) ⁷Li(⁷Li, n)¹³C Q_m = 18.620 E_b = 26.796
(b) ⁷Li(⁷Li, p)¹³B Q_m = 5.965
(c) ⁷Li(⁷Li, d)¹²B Q_m = 3.311
(d) ⁷Li(⁷Li, t)¹¹B Q_m = 6.199
(e) ⁷Li(⁷Li, α)¹⁰Be Q_m = 14.784
(f) ⁷Li(⁷Li, ⁷Li)⁷Li
(g) ⁷Li(⁷Li, ⁸Be)⁶He Q_m = 7.281

These reactions have been studied with E(⁷Li) to 6.5 MeV: see (1970AJ04) for the early references. For E(⁷Li) = 2.3 to 5.8 MeV, the cross section for emission of α₀, α₁ and α₂₊₃₊₄ is found to increase monotonically with energy (1964DZ1A, 1969CA1A). However, (1971WY01) reports several broad structures in the 0° yield of α₀ and α₁ for E(⁷Li) = 2 to 20 MeV: it is suggested that these are neither compound nucleus resonances nor Ericson-type fluctuations but that they are due to a forward-direction cluster transfer process (1971WY01). For reaction (f) see (1978NO1F: 2.0 → 5.5 MeV).

3. ⁹Be(⁶Li, p)¹⁴C Q_m = 15.126

Observed proton groups are displayed in Table 14.6 (in PDF or PS) (1973AJ01). See also (1976AJ04) and ¹⁵N.

4. ⁹Be(⁷Li, d)¹⁴C Q_m = 10.100

Angular distributions of the deuterons to ¹⁴C*(0, 6.09, 6.59 + 6.73, 6.90 + 7.01, 7.34, 8.32) have been measured at E(⁷Li) = 5.6, 5.8, 6.0 and 6.2 MeV (1969SN02). (1969TH01) report E_γ = 6094.5 ± 3.2, 6728.1 ± 1.4 and 7011.7 ± 5.2 keV for the ground state transitions of these states. See also (1976AJ04).

5. ⁹Be(⁹Be, α)¹⁴C Q_m = 17.2511

At E(⁹Be) = 5 MeV ¹⁴C*(0, 6.09, 6.6, 6.9, 7.34, 8.32, 9.80) are populated. The α₀ angular distributions have been measured at 5 and 12 MeV (1977YO02).

6. ⁹Be(¹³C, ⁸Be)¹⁴C Q_m = 6.5114

τ_m for ¹⁴C*(6.09, 6.73, 6.90) are < 10, > 5 × 10⁴ and 36 ± 4 fsec, respectively (1975SE04): see Table 14.4 (in PDF or PS).

7. ¹⁰Be(α, p)¹³B Q_m = -8.818 E_b = 12.0126

A preliminary report of a resonance corresponding to a T = 2 state has not been published: see (1976AJ04).

8. (a) ¹¹B(t, n)¹³C Q_m = 12.4214 E_b = 20.5979
(b) ¹¹B(t, α)¹⁰Be Q_m = 8.585

For possible resonant structure in (a) see (1976AJ04). For reaction (b) see (1977CI1A).

9. ¹¹B(α, p)¹⁴C Q_m = 0.7839

Angular distributions of p₀ have been measured at E_α = 1.43 to 25.1 MeV [see (1976AJ04)] and at E_α = 1.43 to 2.94 MeV (1976DA06) and 4.4 to 6.7 MeV (1978HO08). See also Table 14.4 (in PDF or PS), ¹⁵N and (1976EP1A, 1980DO1C; astrophys.).

10. ¹¹B(⁷Li, α)¹⁴C Q_m = 18.131

At E(⁷Li) = 5 MeV, α-particle groups are observed to the known states of ¹⁴C with E_x < 10 MeV except ¹⁴C*(6.90), and to the unresolved 10.4 - 10.5 MeV states. There is some indication also of ¹⁴C states at (10.71), 11.35, 11.66, (14.15), (14.73) and (15.07) MeV (± approx. 50 keV). Angular distributions have been obtained for the α-particles to ¹⁴C*(0, 6.09, 8.32) (1966MC05).

11. ¹²C(t, p)¹⁴C Q_m = 4.6410

Observed proton groups are displayed in Table 14.7 (in PDF or PS). Angular distributions have been measured at E_t = 5.5 to 23 MeV: see (1976AJ04) and Table 14.6 (in PDF or PS) (1978AJ02, 1978MO07, 1978MO08, 1979PI01). (1978FO06) report that a calculation which treats the positive parity states of ¹⁴C as (sd)² two-neutron states coupled to an inert ¹²C core gives good agreement with the (t, p) strengths and the experimental E_x. τ_m of ¹⁴C*(6.73) is 97 ± 15 psec (1968AL12); the nuclear gyromagnetic ratio is |g| = 0.272 ± 0.007 showing that the state is not of a pure (p^-3_1/2d_5/2) configuration (1974AL07). See also (1977FO1E) and ¹⁵N.

12. ¹²C(α, 2p)¹⁴C Q_m = -15.1731

At E_α = 65 MeV ¹⁴C*(6.73, 10.74) are strongly populated. Angular distributions are measured to ¹⁴C*(0, 6.73, 10.74, 14.9 ± 0.1): the distribution to ¹⁴C*(10.74) is consistent with L = 4 (1976JA13, 1978JA10). See also (1976CE1E).

13. ¹²C(¹⁰B, ⁸B)¹⁴C Q_m = -13.890

At E(¹⁰B) = 100 MeV ¹⁴C*(6.72, 10.74) are strongly populated and the angular distributions to these states are reported. ¹⁴C*(15.0) is also observed (1978HA10).

14. ¹²C(¹²C, ¹⁰C)¹⁴C Q_m = -18.7228

At E(¹²C) = 114 MeV ¹⁴C*(6.73, 10.25) [3^- and 4⁺, respectively] are populated (1972SC21, 1974AN36).

15. (a) ¹²C(¹⁴N, ¹²N)¹⁴C Q_m = -17.494
(b) ¹²C(¹⁶O, ¹⁴O)¹⁴C Q_m = -15.7652
(c) ¹²C(¹⁸O, ¹⁶O)¹⁴C Q_m = 0.9341

For reaction (a) see (1976AJ04). At E(¹⁶O) = 128 MeV angular distributions are reported to ¹⁴C*(0, 6.73, 10.74) [J^π = 0⁺, 3^-, 4⁺] (1979PR07). For reaction (c) see (1976WE05) and (1976AJ04). See also (1976KA04; theor.).

16. ¹³C(n, γ)¹⁴C Q_m = 8.1765
Q₀ = 8176.477 ± 0.047 keV (1979GR1J; prelim.).

The thermal capture cross section is 0.9 ± 0.2 mb (1973MU14, 1974SH1E). The neutron capture yield has been measured from E_n = 95 to 235 keV: see Table 14.8 (in PDF or PS). The (n, γ₀) cross section has also been measured for E_n = 5.6 to 14.0 MeV (1980JE1A). ¹³C is probably not significantly involved as a neutron poison in s-process nucleosynthesis: see (1976AJ04). Two γ-rays are observed in thermal neutron capture with E_γ = 8174 ± 2 and 6093 ± 2 keV [E_x = 6094 ± 2 keV], with intensities of 87 ± 5 and 13 ± 1%. Intensities of transitions via other ¹⁴C states are < 2% (1967TH05). [(1979GR1J; prelim.) find E_γ = 8173.92 ± 0.05 keV].

17. ¹³C(n, n)¹³C E_b = 8.1765

The coherent scattering length (thermal, bound) is 6.19 ± 0.09 fm, σ_scatt = 4.16 ± 0.13 b (1979KO26). The total cross section has been measured for E_n = 0.10 to 9 MeV and 16 to 23 MeV: observed resonances are displayed in Table 14.8 (in PDF or PS). High resolution σ_t measurements by (1979AU07) for E_n = 1.2 to 13.9 MeV are displayed in Fig. 6 of that paper but an analysis in terms of resonances has not been reported. See also (1978LA1H) and (1976GAYV).

18. (a) ¹³C(n, t)¹¹B Q_m = -14.403 E_b = 8.1765
(b) ¹³C(n, α)¹⁰Be Q_m = -3.836

For reaction (a) see (1973BI1B). For reaction (b) see (1970AJ04).

19. ¹³C(p, π⁺)¹⁴C Q_m = -132.173

At E_p = 185 MeV (1973DA37) and 200 MeV (1979HO1F) the angular distributions of π⁺ and π^- to the ground states of ¹⁴C and ¹⁴O are very different. The population of ¹⁴C*(6.09, 8.32, 14.9 ± 0.2) is also reported (1973DA37). For cross-section measurements near threshold see (1979MA38, 1979MA39). See also (1976BO2C, 1979SOZY) and (1976NO1D; theor.).

20. ¹³C(d, p)¹⁴C Q_m = 5.9519

Observed proton groups are displayed in Table 14.9 (in PDF or PS). Angular distributions have been measured at a number of energies up to E_d = 14.8 MeV [see (1976AJ04)] and at E_d-bar = 13 MeV (1978DA17; to ¹⁴C*(0, 6.09, 7.34)). For listings of θ²_n see Table 14.5 (in PDF or PS) in (1970AJ04).

Gamma rays are exhibited in Table 14.5 (in PDF or PS): studies of these, of the angular distributions analyzed by DWBA, and of pγ correlations lead to the following J^π assignments [see reaction 14 in (1970AJ04) for a full discussion of the evidence and of the relevant references]. ¹⁴C*(6.09) is 1^- (decay is E1); ¹⁴C*(6.59) is 0⁺ (internal pairs only); ¹⁴C*(6.73) is 3^- (γ₀ is E3; l_n = 2); ¹⁴C*(6.90) is 0^- (no γ₀; 0.81 MeV cascade via 6.09 is predominantly dipole; γ_0.8 + γ_6.1 correlation is only consistent with J = 0, and plane polarization leads to negative parity); ¹⁴C*(7.34) is 2^- (strength of cascade decay and angular correlation results). See also (1974FI1D) and ¹⁵N.

21. ¹³C(t, d)¹⁴C Q_m = 1.9192

See (1976AJ04).

22. ¹³C(⁷Li, ⁶Li)¹⁴C Q_m = 0.926

At E(⁷Li) = 34 MeV the angular distribution has been measured for the ground state transition. ¹⁴C*(6.09, 6.73) and possibly other states are also populated (1973SC26).

23. ¹³C(¹¹B, ¹⁰B)¹⁴C Q_m = -3.2787

At E(¹¹B) = 114 MeV ¹⁴C_g.s. is weakly excited but ¹⁴C*(6.73, 7.34) [J^π = 3^- and 2^-] are strongly populated (1974AN36).

24. ¹³C(¹³C, ¹²C)¹⁴C Q_m = 3.2302

See (1979KOZZ).

25. (a) ¹³C(¹⁴N, ¹³N)¹⁴C Q_m = -2.377
(b) ¹³C(¹⁵N, ¹⁴N)¹⁴C Q_m = -2.6568

See (1976GA37) and (1976AJ04). See also (1978OS06; theor.).

26. (a) ¹³C(¹⁷O, ¹⁶O)¹⁴C Q_m = 4.032
(b) ¹³C(¹⁸O, ¹⁷O)¹⁴C Q_m = 0.132

Angular distributions have been measured at E(¹⁷O) = 29.8 and 32.3 MeV (1977CH22, 1978CH16) and E(¹⁸O) = 31.0 MeV (1978CH16).

27. ¹⁴B(β^-)¹⁴C Q_m = 20.62

¹⁴B decays primarily to ¹⁴C*(6.09, 6.73): see Table 14.2 (in PDF or PS). The half-life is 16.1 ± 1.2 msec: see ¹⁴B.

28. ¹⁴C(γ, n)¹³C Q_m = -8.1765

See (1976AJ04) and (1979KI11; theor.).

29. ¹⁴C(e, e)¹⁴C

The charge radius of ¹⁴C, r_rms = 2.56 ± 0.05 fm (1973KL12). At E_e = 37, 50 and 60 MeV (θ = 180°), inelastic groups are observed to ¹⁴C*(7.01, 7.34, 8.32, 9.80, 10.5, 11.31 ± 0.02, 12.96, 14.67) with J^π = 2⁺, 2^-, 2⁺, (1), -, 1⁺ and (3, 4), respectively, for the states with 7.0 < E_x < 13.0 MeV. ¹⁴C*(11.31) dominates the spectrum: this 1⁺ state has Γ = 207 ± 13 keV and Γ_γ₀ = 6.8 ± 1.4 eV (1977CR02). There is no evidence of sharp structure in the region E_x = 19 to 24 MeV where the T = 2 analog state of ¹⁴B_g.s. would be expected (1974KL12: E_e = 61.5 and 80.7 MeV). See also (1976AJ04) and (1979KI11, 1980ER01; theor.).

30. (a) ¹⁴C(p, p)¹⁴C
(b) ¹⁴C(d, d)¹⁴C

For reaction (a) see (1976AJ04). Angular distributions have also been studied at E_d = 17 MeV to ¹⁴C*(0, 6.73, 7.01) (1975CE04). See also (1976AJ04).

31. ¹⁴C(³He, ³He)¹⁴C

Elastic angular distributions have been measured at E(³He) = 4.5, 5.1 and 5.8 MeV (1972KE08) and 10, 12, 15 and 18 MeV (1970DU07).

32. ¹⁴C(α, α)¹⁴C

Elastic angular distributions have been studied at E_α = 22, 24 and 28 MeV (1972OE01, 1973OE01).

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

The elastic scattering for reaction (a) has been studied at E(¹²C) = 12, 15, 18 and 20 MeV and for reaction (b) at 15 MeV (1972BO68). Yields of γ-rays from ¹⁴C*(6.73) for E(¹⁴C) = 40 to 57 MeV are reported by (1980FR03).

34. ¹⁴C(¹⁴N, ¹⁴N)¹⁴C

See (1976AJ04).

35. ¹⁴C(¹⁶O, ¹⁶O)¹⁴C

The elastic scattering angular distributions have been measured at E(¹⁶O) = 20, 25 and 30 MeV (1975SC35). See also (1978BE2C) and (1979HE02; theor.).

36. ¹⁴N(π^-, γ)¹⁴C Q_m = 139.410

Branching ratios have been measured for the capture of stopped pions to ¹⁴C*(0, 7.0 ± 0.1, 8.3, 11.3, 20.0 ± 1.0) (1975BA52): the total radiative capture branching is 2.1 ± 0.2%. The preliminary results of (1979AL1M) are in general agreement, but it is suggested that the E_x of the fourth group is 10.7 MeV. See also (1977RI1H, 1979PE1C) and the "GENERAL" section here.

37. ¹⁴N(n, p)¹⁴C Q_m = 0.6259

The p₀ angular distribution has been measured at E_n = 14 MeV (1971CO32). See also ¹⁵N, (1976KI1D, 1978NE1A, 1978NE1B), (1977CO1U: astrophys.) and (1976AJ04).

38. ¹⁴N(t, ³He)¹⁴C Q_m = -0.1379

See (1970AJ04).

39. ¹⁴N(⁷Li, ⁷Be)¹⁴C Q_m = -1.018

See (1976AJ04).

40. (a) ¹⁵N(γ, p)¹⁴C Q_m = -10.2074
(b) ¹⁵N(e, e'p)¹⁴C Q_m = -10.2074

For E_bs = 19.6 to 38.3 MeV, ¹⁴C*(0, 6.1 + 6.6 + 6.9, 7.0, 10.7) are preferentially excited (1972DE1D, 1976PA22). See also ¹⁵N. For reaction (b) see (1975MU07).

41. ¹⁵N(n, d)¹⁴C Q_m = -7.9828

Ground state angular distributions have been measured for E_n = 14.1 - 14.8 MeV: see (1976AJ04) and (1978BA1M). See also ¹⁶N in (1982AJ01).

42. ¹⁵N(d, ³He)¹⁴C Q_m = -4.7139

¹⁴C states populated in this reaction are displayed in Table 14.9 (in PDF or PS) of (1976AJ04), together with l and C²S values (1971KA35: E_d = 52 MeV).

43. ¹⁵N(t, α)¹⁴C Q_m = 9.6066

See (1976AJ04).

44. ¹⁶O(π^-, np)¹⁴C Q_m = 116.449

At E_π^- = 230 MeV, γ-rays from the population of ¹⁴C*(6.73, 6.90) are observed (1974LI15).

45. ¹⁶O(⁶Li, ⁸B)¹⁴C Q_m = -16.592

At E(⁶Li) = 93 MeV ¹⁴C*(0, 7.01, 8.32, 10.45) are populated, the first two of these strongly (1976WE09, 1977WE1B).

46. ¹⁶O(¹¹B, ¹³N)¹⁴C Q_m = -4.435

See (1976AJ04).

47. ¹⁶O(¹⁸O, ²⁰Ne)¹⁴C Q_m = -1.4970

Angular distributions are reported at E(¹⁸O) = 28 and 32 MeV (1971BA68) and 36.1 MeV (1977KA26).

48. ¹⁷O(n, α)¹⁴C Q_m = 1.8167

See ¹⁸O in (1978AJ03).

49. ¹⁸O(γ, α)¹⁴C Q_m = -6.2279

At E_bs = 23.5 and 28 MeV ¹⁴C*(6.09, 6.73) are excited (1976BA41). See also ¹⁸O in (1978AJ03).

50. ¹⁸O(d, ⁶Li)¹⁴C Q_m = -4.7544

See (1978BE1H) and (1976AJ04).

51. ¹⁹F(d, ⁷Be)¹⁴C Q_m = -7.142

See (1976AJ04).