Low-energy electron collisions with O2: Test of the molecular R-matrix method without diagonalization

摘要

Electron collisions with O2 at scattering energies below 1 eV are studied in the fixed-nuclei approximation for anrange of internuclear separations using the ab initio molecular R-matrix method. The 2u0002g scattering eigenphasesnand quantum defects are calculated. The parameters of the resonance and the energy of the bound negativenion are then extracted. Different models of the target that employ molecular orbitals calculated for the neutralntarget are compared with models based on anionic orbitals. A model using a basis of anionic molecular orbitalsnyields physically correct results in good agreement with experiment. An alternative method of calculation of thenR matrix is tested, where instead of performing a single complete diagonalization of the Hamiltonian matrix innthe inner region, the system of linear equations is solved individually for every scattering energy. This approachnis designed to handle problems where diagonalization of an extremely large Hamiltonian is numerically toondemanding.