The lifetimes of the $J^{\pi }=0^{+} 6590$-keV and $J^{\pi }=3^{-} 6728$-keV states in ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and the $J^{\pi }=3^{-} 5834$-keV state in ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ were measured using the recoil distance method. Gamma rays following the $\mathrm{pn}$ and $2n$ evaporation channels from ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ + ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ reactions were detected at ${\theta }_{\gamma }=0\mathrm{}°$. The experimental results are ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(${6590,0}^{+}$), $\tau =3.7\mathrm{}\pm 0.9$ ps; ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(${6728,3}^{-}$), $\tau =96\mathrm{}\pm 15$ ps; ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(${5834,3}^{-}$), $\tau =12.9\mathrm{}\pm 1.9$ ps. Extensive shell-model calculations for both ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ have been performed using an SU(3) basis and are compared to these and other experimental results.

NUCLEAR REACTIONS ${}_{}{}^7{}_{}{}^{}\mathrm{Li}({}_{}{}^9{}_{}{}^{}\mathrm{Be},pn\gamma )$ $E_{\mathrm{Be}}=5.5\mathrm{}$ MeV; ${}_{}{}^9{}_{}{}^{}\mathrm{Be}({}_{}{}^7{}_{}{}^{}\mathrm{Li},pn\gamma )$ and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}({}_{}{}^7{}_{}{}^{}\mathrm{Li},2n\gamma )$ $E_{\mathrm{Li}}=3.8\mathrm{}-7.8$ MeV; measured $E_{\gamma }$,$I_{\gamma }$ (recoil distance method); calculated $\tau$ from theory and compared with experiment.

• Received 11 September 1980

DOI:https://doi.org/10.1103/PhysRevC.23.1571