Electron Correlation and Nuclear Motion Corrections to the Ground-State Energy of Helium Isoelectronic Ions from Li to Kr

Abstract

Nonrelativistic energies for the ground state of helium isoelectronic ions with Z = 2–54 are computed. Calculations are performed using explicitly correlated wavefunctions of a generalized Hylleraas type. The variational procedure used allows solving the two-electron Schrödinger equation with a practically unlimited number of parameters, for trial wavefunctions expanded in products of positive powers of the Hylleraas coordinates. A non-conventional optimization procedure, involving nonlinear programming, is applied. The contribution of the various terms is assessed, including nuclear finite mass and polarization corrections. Our results are compared to other theoretical results. Combined with noncorrelated relativistic energies, they yield good agreement with available experimental data.