Interaction Energy Curves of LiHe and NaHe (X 2Σ+, A 2Π, B 2Σ+) and X 1Σ+ Ions

Abstract

Hartree–Fock interaction energy curves have been calculated for the X 2Σ+, A 2Π, and B 2Σ+ states of neutral LiHe and NaHe as well as for the ground state X 1Σ+ ions over a range of distances from 3 to 10 a.u. Since it is intended to apply these results to scattering problems, the variation of the dipole and quadrupole moments and the electronic transition probabilities with internuclear distance were also obtained. Both Slater-type functions and Gaussian-type functions were used as variational trial functions with the intention of gauging the efficacy of the Gaussian basis. Except for situations involving small energy minima the Gaussian basis yielded results accurate relative to the Slater basis. The features of the Hartree–Fock interaction energy curves can be summarized as follows: (1) The X 2Σ+ interaction energy is purely repulsive for both molecules to the accuracy of the present calculation. (2) The A 2Π and X 1Σ+ curves are strikingly similar for both Li and Na confirming the penetration of the He for this interatomic orientation. (3) The long-range repulsive behavior of the B 2Σ+ curve compared with estimates of the correlation energy shows that the internuclear distance dependence of the energy in the region of 10 a.u. is dominated by the Hartree–Fock repulsive curve. Charge-density plots have been obtained for all states and distances. These are used to illustrate the physical basis of the energy curves.