A recent measurement of the magnitude of quadrupole moment of the ground state of ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$, $Q\left({}_{}{}^9{}_{}{}^{}\mathrm{Li}\right)$, finds that $\left|\frac{Q\left({}_{}{}^9{}_{}{}^{}\mathrm{Li}\right)}{Q\left({}_{}{}^7{}_{}{}^{}\mathrm{Li}\right)}\right|=0.88\mathrm{}\pm 0.18$. A variety of shell-model calculations, using $p$-shell wave functions, predict $Q\left({}_{}{}^9{}_{}{}^{}\mathrm{Li}\right)\simeq 1.3Q\left({}_{}{}^7{}_{}{}^{}\mathrm{Li}\right)$ and yield quadrupole moments whose magnitudes are approximately half the experimental values. Agreement between theory and experiment is improved when effective charges are used, although the results are still not completely satisfactory. A calculation of the wave functions of the low-lying states of ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$ using a modified version of the Sussex matrix elements in a model space, including all $0\hslash \omega$ and $2\hslash \omega$ excitations, has been performed. The resulting value for $Q\left({}_{}{}^9{}_{}{}^{}\mathrm{Li}\right)$ was —3.46 ${\mathrm{fm}}^2$ as compared with the experimental value of ±3.22±0.66 ${\mathrm{fm}}^2$. The effective charge used in the calculation, $0.28e$, reproduced the experimental value of $Q\left({}_{}{}^7{}_{}{}^{}\mathrm{Li}\right)$ exactly. The calculated magnetic dipole moment of the ground state of ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$ is $3.32 {\mu }_N$ the experimental value is $\pm 3.44 {\mu }_N$.

• Received 9 May 1984

DOI:https://doi.org/10.1103/PhysRevC.30.1320