The low-lying negative parity states of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ are interpreted as arising from a $p_{\frac{3}{2}}$ hole coupled to the ground state and first excited state of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. The coupling interaction has been expanded in a series of spherical tensor operators including dipole and quadrupole terms. The parameters of the interaction are found by fitting to the experimental energies, moments, and transition rates of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$. The calculated $\beta$ decay $log\mathrm{ft}$ value and most of the calculated static moments and transition rates are in excellent agreement with experiment. The exceptions are attributed to the limited basis used and to the fact that the free core and single particle operators are used; that is no effective operators are used. An improvement in energies and in one transition rate is obtained by treating ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ as a rotator and including a third core state. Possible improvements in the model are discussed.

NUCLEAR STRUCTURE ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$. Calculated energies, moments, transition rates, $log\mathrm{ft}$, negative parity states.

• Received 26 March 1974

DOI:https://doi.org/10.1103/PhysRevC.10.84