Pseudo-bound-state study of low-energy electron-molecule collisions: Elastice-H2scattering

A study of the low-energy elastic $e$-${\mathrm{H}}_2$ scattering information contained in multiconfiguration variational wave functions for a low-lying (positive) energy of the ${\mathrm{H}}_2^{-}$ system is described. The wave function is calculated using standard bound-state techniques, employing the modified valence-bond method with a basis set of Slater-type orbitals, and from it are obtained starting values at moderate electron-molecule separations for a simple single-channel scattering calculation, which is carried out beyond the region where exchange and coupling of partial waves are thought to be important. Results are presented for $s_{\sigma }$ elastic scattering for incident-electron energies ≤ 10 eV in the static-exchange approximation with polarization included by means of an adiabatic polarization potential. The study shows that the standard ${\mathrm{H}}_2^{-}$ variational function does indeed provide a good approximation to the elastic scattering wave function in the region close to the molecule, but that care must be taken in choosing the basis set. Comparisons are made with other more traditional calculations.