
^{15}C (1959AJ76)(See the Energy Level Diagram for ^{15}C) GENERAL: See also Table 15.1 [Table of Energy Levels] (in PDF or PS). Mass of ^{15}C: From the Q of the ^{14}C(d, p)^{15}C reaction given by (1956DO41) (Q_{0} = 1.007 ± 0.001 MeV), and using the Wapstra masses for ^{14}C, d and ^{1}H, the mass excess of ^{15}C is 14.305 ± 0.005 MeV. Application of Coulomb corrections indicates an excitation of 11.72 to 11.87 MeV for the first T = 3/2 state of ^{15}N (1956BA16, 1956DO37, 1957MU99).
The halflife is 2.25 ± 0.05 sec. The βspectrum is complex, with 32 ± 2 % of transitions (log ft = 6.0) to the ^{15}N ground state (E_{β}(max) = 9.82 ± 0.04 MeV) and 68% (log ft = 4.1) to the upper of the 5.3 MeV levels of ^{15}N. A 5.299 ± 0.006 MeV γray is observed (1959AL1M): no other γrays with E_{γ} > 5.3 MeV are observed with intensities > 5%, and the intensity of a 1.9 MeV γray (expected if the ^{15}N*(7.16) level were involved) is < 10% (1956DO37). The internal pair conversion coefficient of the 5.30 MeV γray is consistent with E1. All data are consistent with J = 1/2^{+} for the 5.305 MeV state in ^{15}N and J = 1/2^{+} for ^{15}C (1959AL1M). See also (1955AJ61, 1956BA16, 1956DO37).
At E(^{7}Li) = 2.0 MeV (θ = 90°) proton groups are observed corresponding to the ground state of ^{15}C and to excited states at 0.62 ± 0.06, 2.48 ± 0.05, 3.08 ± 0.04, 4.26 ± 0.04, 5.93 ± 0.04, 6.58 ± 0.04, and 8.16 ± 0.06 MeV. The ground state Q is 9.04 ± 0.05 MeV (1957MU99). In an earlier experiment, (1957NO14) found Q_{0} = 9.05 ± 0.05 and Q_{1} = 8.35 ± 0.05 MeV (E_{x} = 0.70 ± 0.05 MeV). Calculation of Coulomb and (n  ^{1}H) energy difference places the analogue state of ^{15}N at 11.72 to 11.87 MeV. Identification with the known J = 1/2^{+}; T = 3/2 level of ^{15}N at 11.61 MeV supports J = 1/2^{+} for ^{15}C_{g.s.} (1956BA16, 1957MU99, 1957NO14).
Identification of ^{15}C_{g.s.} with ^{15}N*(11.62), J^{π} = 1/2^{+}; T = 3/2, is suggested by (1956BA16). Proton groups corresponding to the ground state and to levels at 0.7 ± 0.1 and 6.2 ± 0.15 MeV are reported by (1958MO95). The weak activity previously reported at E_{d} < 1.3 MeV, indicating a Q ≈ 0.1 MeV (see (1955AJ61)), is now attributed to contamination (1956BO1L). See also ^{16}N.
The capture cross section is < 1 μb (1951YA1A, 1955HU1B, 1958HU18). The following reactions leading to ^{15}C are not reported: ^{13}C(t, p)^{15}C (Q_{m} = 0.909), ^{14}C(t, d)^{15}C (Q_{m} = 5.039), ^{14}C(α, ^{3}He)^{15}C (Q_{m} = 19.358), ^{15}N(n, p)^{15}C (Q_{m} = 8.994), ^{18}O(n, α)^{15}C (Q_{m} = 5.024).
