Energy Levels of Light Nuclei A = 14 - Triangle Universities Nuclear ...

Observed resonances are displayed in Table 14.16. The radiative decay is exhibited in Table
14.11.
The low-energy capture cross section yields an extrapolated S-factor at E p = 25 keV (c.m.),
S 0 =6.0 ± 0.8 keV· b. The capture cross section rises from (7.7 ± 1.8) × 10 −10 batE p = 100 keV
to (9.8 ± 1.2) × 10 −9 batE p = 140 keV: see (70AJ04).
Following is a summary of the reasons for the assignments of J π ; T to some of the lower resonances
displayed in Table 14.16: for a fuller discussion and complete references see (70AJ04, 76AJ04,
81AJ01). 14 N(7.97): angular distribution of the γ-rays is consistent with J π =2 − , 14 N*(8.06):
width of resonance, isotropy of γ-rays show l p =0;J π =1 − from 13 C(p, p); E1 transition to g.s.
is uninhibited; therefore, T = 1 [but 1.4% 8.06 → 2.31 transition [E x = 2312.6 ± 0.3 keV]shows
T = 0 admixture: α 2 =0.046]. The strong transition 8.06 → 5.69 [3.5%] permits either E1 or
M1, ∆T =1. Since5.69 → 2.31 is seen 14 N*(5.69) cannot have J π =0 + ,and2 + is excluded
by the strength of the 8.62 → 5.69 transition. It is then J π =1 − ; T = 0 [the isospin mixing
α 2 =0.09]; E x = 5691.55 ± 0.13 keV (81BI17). 14 N*(8.49, 8.96, 9.13) correspond to anamolies in
the cross section. The nature of their γ-decays [see Table 14.11] and the angular distribution leads
to J π =4 − ,5 + ,3 + [all T = 0], respectively.
14 N*(8.62) [J π =0 + from 13 C(p, p)] shows strong transitions to 14 N*(0, 3.95, 5.69): T =1.
The strength of the 8.62 → 3.95 decay shows it is dipole and therefore J =1for 14 N*(3.95)
[E x = 3947.6 ± 0.4 keV]. The strength of the transition 8.62 → 6.20 and the angular correlation
8.62 → 6.20 →g.s. is consistent with J π =1 + , T =0for 14 N*(6.20) [E x = 6203.7 ± 0.6 keV].
14 N*(8.78) [J π =0 − from 13 C(p, p)] has a large Γ γ consistent with E1 and T =1. 14 N*(9.17):
angular correlation and angular distribution measurements indicate J π =2 + for that state, 3 − for
14 N*(6.45) [see however Table 14.10] andJ =2for 14 N*(7.03). For recent studies of 14 N*(9.17) see
(81BI17, 86WA13): E x = 9172.5 ± 0.3 keVfromE γ ,Γ γ0 /Γ γ =(79± 4)%, Γ [from (p, p)]= 135 ± 8
eV [135 ± 11 eV in (γ, γ)]. Other E x determined by (81BI17) are 2312.90 ± 0.03, 3948.2 ± 0.2,
5105.9 ± 0.3, and 6446.3 ± 0.2 keV. See also Tables 14.11 and 14.14.
The angular distribution of the γ-rays from 10.23 → 2.31 is consistent with J π = 1 + for
14 N*(10.23): T = 0 from M 2 (M1) [see, however, Table 14.10]. The γ 0 angular distribution
is consistent with J =2for 14 N*(10.43): the similar decay characteristics of this state and of
14 N*(9.17) suggest that they are both J π =2 + , T =1.
Below E p =5.5 MeVonlyγ 0 can be observed in the capture radiation. A number of resonances
in the γ 0 yield and in the yield of the ground-state γ-rays from 13 C*(3.09, 3.68, 3.85) have been
observed: these are shown in Table 14.16 in the range E p =3.7 to 6.6 MeV. Angular distributions
and measurements of Γ γ0 lead to the J π values shown. Above E p =7MeVtheγ 0 yield shows
broad structure and the giant dipole resonance at E x =22.5 and 23.0 MeV. Measurements of the
γ 0 and γ 1 90 ◦ yields for E x =23to33MeVfindthattheT = 2 resonances reported earlier at
E x =23.7 and 24.2 MeV do not exist and that there is no evidence for the T = 2 GDR between
E x = 25 and 29 MeV. The 90 ◦ yields of γ-rays to T =0states(4.9