VariationalR-matrix calculations for singly and doubly excited singlet gerade channels inH2

Abstract

Variational ab initio R-matrix theory is combined with generalized multichannel quantum defect theory, implemented in spheroidal coordinates, to calculate clamped-nuclei {sup 1}{sigma}{sub g}{sup +}, {sup 1} product {sub g}, and {sup 1}{delta}{sub g}{sup +} electron-ion scattering phase shift matrices for H{sub 2}. The calculations cover the bound state region below H{sub 2}{sup +} 1{sigma}{sub g}, the resonance region between H{sub 2}{sup +} 1{sigma}{sub g} and H{sub 2}{sup +} 1{sigma}{sub u}, and they extend beyond the H{sub 2}{sup +} 1{sigma}{sub u} threshold. They span the range of internuclear distances 1{<=}R{<=}5 a.u. The use of spheroidal instead of spherical coordinates allows a restricted partial wave expansion to be used, thus yielding a compact set of interaction parameters pertaining to the electron-ion scattering dynamics in H{sub 2}. The accuracy of our fixed-nuclei quantum defects is generally of the order of about 0.02. At the same time the quantum defect matrices obtained here exhibit a smooth behavior across the ionization thresholds and their elements also vary rather smoothly with internuclear distance. These results represent a step toward the goal of constructing a unfied theoretical description of ionization and dissociation fragmentation dynamics of H{sub 2}.