Study of the Nuclear Quadrupole Interaction in the Excited (2P3) State of the Beryllium Atom by Many-Body Perturbation Theory

Abstract

The linked-cluster many-body perturbation theory with a $V^{\mathrm{N}-1\mathrm{}}$ potential has been applied to study the nuclear quadrupole interaction for the ${\mathrm{Be}}^9$ atom in the excited ($1s^{2}2s2p {}_{}{}^3{}_{}{}^{}P$) state. The first- and second-order shielding contributions to the field gradient are found to be 3.8% and — 2.0%, respectively. The former involves cancellations among $1s$ and $2s$ states and direct and exchange contributions with individual effects running as large as 12%. From these field-gradient results and the experimental quadrupole constant, the nuclear quadrupole moment of ${\mathrm{Be}}^9$ has been evaluated as 0.0525±0.0003 b.