Study of rigid-rotor exact exchange electron - scattering using the first-order non-degenerate adiabatic theory

Abstract

We have applied the first-order non-degenerate adiabatic (FONDA) theory to electron - scattering with exchange treated rigorously. The pure rotational body-frame and the laboratory-frame FONDA cross sections are calculated and compared with our body-frame fixed-nuclei (BF-FN) and adiabatic-nuclei (AN) results, respectively. For consistency, all the scattering calculations performed are based on identical potential models and values of input-scattering parameters. These comparisons reveal significant differences between the pure rotational FONDA and BF-FN and AN results near threshold energy range. For instance, the laboratory-frame FONDA (LF-FONDA) and AN cross sections differ by 54, and 117% for to j = 2 and to j = 4 excitations, respectively at 0.01 eV. The body-frame FONDA (BF-FONDA) and BF-FN results are also different by 53, 81, 10 and 96% at 0.0027 eV in the , , and symmetries, respectively. These differences stem from the breakdown of the target-state degeneracy assumption near threshold energy range. We also compare our cross sections for the - system with previously published results. We conclude that stable rotational excitation cross sections require significantly higher values of convergence parameters than previously used.