Inclusion of nonadiabiatic effects in calculations on vibrational excitation of molecular hydrogen by low-energy electron impact

Abstract

The nonadiabatic phase matrix method offers a unified, systematic treatment of vibrational dynamics in calculations of low-energy inelastic electron-molecule cross sections. This formalism uses fixed-nuclei R matrices to describe the region of configuration space near the target but—unlike its fully adiabatic counterpart, the energy-modified adiabatic method—includes nonadiabatic effects, which are important for resonant scattering and near a vibrational threshold. A most stringent test of this method is [Formula Presented] scattering below 10 eV, where elastic and inelastic cross sections exhibit an enhancement around 3 eV which at the fixed-nuclei level involves a range of physical effects, from nonresonant to resonant scattering, as the internuclear separation varies from the smallest to largest relevant values. Here we describe an implementation of this method appropriate to such systems, an assessment of its accuracy for [Formula Presented] scattering, and an appraisal of the importance of nonadiabatacity for the [Formula Presented] and [Formula Presented] vibrational excitations. © 1999 The American Physical Society.