Configuration-interaction calculations of positron binding to group-II elements

The configuration-interaction (CI) method is applied to the study of positronic magnesium (e⁺Mg), positronic calcium (e⁺Ca), and positronic strontium (e⁺Sr). The CI expansion was seen to converge slowly with respect to L_max, the maximum angular momentum of any orbital used to construct the CI basis. Despite doing explicit calculations with L_max=10, extrapolation corrections to the binding energies for the L_max→∞ limit were substantial in the case of e⁺Ca (25%) and e⁺Sr (50%). The extrapolated binding energies were 0.0162 hartree for e⁺Mg, 0.0165 hartree for e⁺Ca, and 0.0101 hartree for e⁺Sr. The static-dipole polarizabilities for the neutral parent atoms were computed as a by-product, giving 71.7a₀³, 162a₀³, and 204a₀³ for Mg, Ca, and Sr, respectively.