Calculating vibrational-excitation cross sections off the energy shell: A first-order adiabatic theory.

Abstract

We report the implementation of a first-order nondegenerate adiabatic theory for vibrational excitation of ${\mathrm{H}}_{2}$ by electrons with energies from threshold to 10 eV. Solution of the scattering equations in this method is far simpler than in a full close-coupling calculation because the method is based on an adiabatic factorization of the electron-molecule scattering ket. The method, however, yields low-energy cross sections that are far more accurate than those of traditional adiabatic-nuclei approximations because its transition matrix is calculated off the energy-momentum shell.