The electric-quadrupole moment $Q$ of the ${\mathrm{Li}}^7$ nucleus has been calculated on the basis of the Wigner supermultiplet theory with configuration mixing that preserves the partition symmetry and $\mathrm{LS}$ coupling. The experimental value of $Q$ can be obtained with an ad hoc mixture of configurations in which the $p$ shell alone is excited and in which the ground configuration is predominant (65%). The linearly independent symmetrized seven-nucleon wave functions for the ${}_{}{}^{22}{}_{}{}^{}P\mathrm{}[4+3]\mathrm{}$ states arising from the $1s^{3}1p^{3}1d$ configuration have been constructed and the matrix elements of $Q$ evaluated. The experimental value of $Q$ can be obtained with ad hoc mixtures of $1s^{4}1p^3$, $1s^{4}1p^{2}2p$, $1s^{4}1p^{2}1f$, and $1s^{3}1p^{3}1d$ in which the proportion of the ground configuration is over 85%. All of the electromagnetic and beta-decay properties of the $A=7\mathrm{}$ nuclei are explained on this model.

• Received 23 July 1965

DOI:https://doi.org/10.1103/PhysRev.140.B1197