The mass excess of ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ has been measured to be 23.657±0.030 MeV using the reaction ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$)${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ at $E\left({}_{}{}^7{}_{}{}^{}\mathrm{Li}\right)=52\mathrm{}$ MeV; this shows that ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ is bound by nearly 1 MeV against neutron emission. Five excited states were also observed at 0.74±0.04, 1.38±0.03, 1.82±0.06, 2.08±0.05, and 2.97±0.04 MeV. The low-lying level structure of ${}_{}{}^{14}{}_{}{}^{}\mathrm{B}$ was found to be similar to the known negative-parity spectrum of ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$.

• Received 11 June 1973

DOI:https://doi.org/10.1103/PhysRevLett.31.395