Ab initio calculations of low-energy electron scattering by HCN molecules.

Abstract

We report results for vibrationally elastic scattering over the energy range 0.0006--11.6 eV. The interaction potential is composed of a near-Hartree-Fock static term plus a parameter-free model of the correlation-polarization potential. The exchange interaction is included exactly through a separable expansion. Results with a model-exchange potential (free-electron-gas plus orthogonalization) are also reported. A resonance appears in Pi symmetry near 2.7 eV (width 1.9 eV) that may be the same feature observed in several experiments. In the model-exchange calculation the Pi resonance is shifted toward higher energy (3.8 eV, width 2.4 eV). The ..sigma.. symmetry was also found to be very sensitive to the treatment of exchange and to the effect of polarization. Differential and rotational excitation cross sections are evaluated in the multipole-extracted adiabatic-nuclei approximation. Results are compared with the available experimental and theoretical data.