A target of BeO, enriched to 94% in ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$, has been bombarded with 31-MeV ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ ions, and delayed activities were measured by means of a fast beam chopper and a NaI(Tl)-plastic $\gamma -\beta$ coincidence detecting system. $\gamma$ rays corresponding to the known activities ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}$, ${}_{}{}^{20}{}_{}{}^{}\mathrm{F}$, and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ were observed in coincidence with $\beta$ rays. In addition, the spectrum contained $\gamma$ rays of 6.1 and 6.7 MeV decaying with $T_{\frac{1}{2}}=16.1\mathrm{}\pm 1.2$ msec. The 6.1-MeV $\gamma$ rays are in coincidence with $\beta$ rays having $E_{max}=14.0\mathrm{}\pm 0.7$ MeV. This activity is assigned to ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ produced in the ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}({}_{}{}^6{}_{}{}^{}\mathrm{Li},2p){}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ reaction. Based on the observed $\gamma$-ray intensities the ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ $\beta$-ray branches to ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ states at 6.09 ($1^{-}$), 6.73 ($3^{-}$), and 7.34 ($2^{-}$) MeV are 81 ± 9%, ${8.6}_{-4.0\mathrm{}}^{+1.7\mathrm{}}$%, and <11%, respectively, where an allowance of 5% has been made for a probable ground-state $\beta$-ray branch. It is deduced that ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ has a spin-parity of $J^{\pi }=2^{-}$ consistent with recent shell-model calculations. The experimental $log\mathrm{ft}$ values for the β decay of ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ are also in good agreement with theory.

RADIOACTIVITY ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$: measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $E_{\beta }$, $\gamma -\beta$ coin; deduced $J^{\pi }$ of ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$, $\beta$ branches, $log\mathrm{ft}$ values; compared with theory.

• Received 24 April 1974

DOI:https://doi.org/10.1103/PhysRevC.10.912