Ab initio electron-molecule scattering theory including polarisation: vibrational and vibrational-rotational excitation of H2

Abstract

An ab initio L2-basis-set theory for low-energy electron-molecule scattering, recently proposed and tested for e-H2 elastic scattering and rotational excitation, is applied to pure vibrational and vibrational-rotational excitation of H2 by slow electrons (0.6-10 eV). An optical potential including direct, exchange and polarisation terms is expanded in a diagrammatic perturbation series and used in the framework of the T-matrix expansion method of Rescigno et al. (1974). Polarisation is shown to have a substantial effect at the lower end of the energy range, decreasing at higher energy and practically vanishing at 10 eV. Calculated integral and differential cross sections for both vibrational and vibrational-rotational excitation are in good agreement with experiment.