Accurate adiabatic potentials ofthe two lowest1g states of He2+2

Abstract

Accurate, explicitly correlated variational wavefunctions are constructed for the two lowest 1g states of He2+2. Born-Oppenheimer potentials, adiabatic corrections and non-adiabatic couplings between both states are computed for internuclear separations from 0.4 to 25.0 a0. The Born-Oppenheimer potentials are compared with existing published results and, in the case of the ground state, disturbing discrepancies are found. It is argued that some of the generally accepted results in the literature are numerically inaccurate. Approximate positions of the lowest resonances in the electronic ground state are determined and it is shown that adiabatic corrections strongly affect these positions.