Complex optical potential model for electron-molecule scattering, elastic scattering, and rotational excitation of H₂ at 10-100 eV

We report nonempirical calculations for differential and integral elastic scattering cross sections, absorption cross sections (accounting for electronic inelasticity), and total scattering cross sections for electron-H₂ scattering at 10-100 eV. The calculations are based on a complex, energy-dependent effective potential consisting of four terms: A static potential calculated from ab initio extended-basis-set Hartree-Fock (EBSHF) wave functions, a polarization potential calculated from an ab initio EBSHF adiabatic polarization potential modified by the local-kinetic-energy semiclassical polarization model to account for nonadiabatic effects, an exchange potential calculated from the EBSHF static electron density and static potential by the semiclassical exchange approximation, and an imaginary absorption potential calculated from the EBSHF static electron density and static potential by the quasifree scattering model with Pauli blocking. We obtain good agreement with all available experimental data at impact energies 10, 40, and 100 eV. Additional calculations with simplified potentials show that nonadiabatic effects on the real polarization potential and the inclusion of an imaginary absorption potential are both essential to the success of the theory except for the large-angle scattering at the highest energy, where the calculated absorption effect is too strong.