Large-dimension configuration-interaction calculations of positron binding to the group-II atoms

Abstract

The configuration-interaction (CI) method is applied to the calculation of the structures of a number of positron binding systems, including ${e}^{+}\mathrm{Be}$, ${e}^{+}\mathrm{Mg}$, ${e}^{+}\mathrm{Ca}$, and ${e}^{+}\mathrm{Sr}$. These calculations were carried out in orbital spaces containing about 200 electron and 200 positron orbitals up to $\ensuremath{\ell}=12$. Despite the very large dimensions, the binding energy and annihilation rate converge slowly with $\ensuremath{\ell}$, and the final values do contain an appreciable correction obtained by extrapolating the calculation to the $\ensuremath{\ell}\ensuremath{\rightarrow}\ensuremath{\infty}$ limit. The binding energies were 0.00317 hartree for ${e}^{+}\mathrm{Be}$, 0.0170 hartree for ${e}^{+}\mathrm{Mg}$, 0.0189 hartree for ${e}^{+}\mathrm{Ca}$, and 0.0131 hartree for ${e}^{+}\mathrm{Sr}$.