The recently determined electric quadrupole moment $Q$ of the ${\mathrm{Li}}^7$ nucleus disagrees with the predictions of current nuclear models. It is shown that the quadrupole and magnetic moments, together with the Gamow-Teller matrix element for the ${\mathrm{Be}}^7$→${\mathrm{Li}}^7$ (ground state) $K$ capture, can be accounted for on the supermultiplet theory if the ad hoc wave function has a 65% admixture of the ${}_{}{}^2{}_{}{}^{}P\mathrm{}\left[3\right]\mathrm{}$ states arising from the $1s^{4}1p^{2}2p$ (two) and $1s^{4}1p^{2}1f$ (one) configurations. Assuming equal configuration admixtures in both levels of the ground doublet term (${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2},\frac{3}{2}}^{}{}_{}{}^{}$), the $M1\mathrm{}$ and $E2\mathrm{}$ transition strengths for quantum jumps between the ground state (${}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{}$) and the first excited state (${}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^{}{}_{}{}^{}$) at 478 keV have been calculated and found to agree with measured values of $B\left(M1\mathrm{}\right)\mathrm{}$ and $B\left(E2\mathrm{}\right)\mathrm{}$ within experimental error. The reduced $E2\mathrm{}$ transition strength in emission is given by: $B\left(E2\mathrm{}\right)\mathrm{}\cong Q^2$. Pure $\mathrm{LS}$ coupling and exact partition symmetry are assumed. The proportion of the ground configuration can be substantially increased by including the $1s^{3}1p^{3}1d$ configuration in the mixture.

• Received 29 January 1965

DOI:https://doi.org/10.1103/PhysRev.139.B300