C13(p, γ)N141.47- and 2.11-Mev Resonances and the Odd-Parity Levels of Mass 14

Abstract

A study has been made of the $\gamma$ rays emitted by the 8.9- and 9.5-Mev levels of ${\mathrm{N}}^{14}$ using the ${\mathrm{C}}^{13}(p, \gamma ){\mathrm{N}}^{14}$ reaction at the 1.47- and 2.11-Mev resonances. The decay schemes of these levels were reinvestigated using a three-crystal pair spectrometer, NaI(Tl) single-crystal measurements, and standard $\gamma -\gamma$ coincidence techniques. The anisotropies relative to the bombarding beam of most of the observed $\gamma$ transitions were measured using the three-crystal pair spectrometer. The angular distributions of some of the $\gamma$ transitions were measured using a single NaI(Tl) crystal. Measurements were made of the Doppler shifts of the ground state decay of the ${\mathrm{N}}^{14}$ 5.10-Mev level and the cascade from the ${\mathrm{N}}^{14}$ 5.83-Mev level to the ${\mathrm{N}}^{14}$ 5.10-Mev level. From these Doppler shift measurements the mean lifetime of the ${\mathrm{N}}^{14}$ 5.83-Mev level was found to be in the range (5.65)×${10}^{-14\mathrm{}}$ sec; while an upper limit of 3×${10}^{-13\mathrm{}}$ sec was set on the mean life of the ${\mathrm{N}}^{14}$ 5.10-Mev level. The results of the study of the $\gamma$ decay of the ${\mathrm{N}}^{14}$ 9.5- and 8.9-Mev levels combined with the results of earlier measurements give conclusive assignments of $2^{-}$, $3^{-}$, 3, and 2 for the ${\mathrm{N}}^{14}$ levels at 9.50, 8.90, 5.83, and 5.10 Mev. The 5.83-Mev level most probably has odd parity. A tentative assignment of $J=2\mathrm{}$ is given to the ${\mathrm{N}}^{14}$ 7.02-Mev level. Evidence is presented, from this and previous investigations, that indicates the ${\mathrm{N}}^{14}$ 8.06-, 8.70-, 8.90-, and 9.50-Mev levels arise from the $s^4{p}^{9}2s$ and $s^4{p}^{9}d$ configurations with the largest contribution being from the ($p_{\frac{1}{2}}2s_{\frac{1}{2}}$) configuration for the 8.06- and 8.70-Mev levels and from the ($p_{\frac{1}{2}}{d}_{\frac{5}{2}}$) configuration for the 8.90- and 9.50-Mev levels. The analogs of these $T=1\mathrm{}$ levels in ${\mathrm{C}}^{14}$ are almost certainly the ${\mathrm{C}}^{14}$ 6.09-, 6.89-, 6.72-, and 7.35-Mev levels, respectively. The $T=0\mathrm{}$, $s^4{p}^{9}2s$ and $s^4{p}^{9}d$ states of ${\mathrm{N}}^{14}$ are also discussed. It is proposed that the 4.91-, 5.69-, 5.10-, and 5.83-Mev levels of ${\mathrm{N}}^{14}$ are $0^{-}$ and $1^{-}$, $s^4{p}^{9}2s_{\frac{1}{2}}$ and $2^{-}$ and $3^{-}$, $s^4{p}^9{d}_{\frac{5}{2}}$ states, respectively.