R-matrix calculations of vibrationally resolved positron-N2 scattering cross sections

Abstract

The molecular R-matrix method has been used to perform ab initio positron-N2 scattering calculations in the fixed-nuclei approximation. Various treatments of polarization and correlation effects have been studied, including the introduction of up to 22 polarized pseudostates. A model in which the N2 comprised an SCF ground state and 10 excited pseudostates was adopted for 12 internuclear geometries ranging from 1.6 to 2.9 a0. Vibrationally elastic and inelastic cross sections are obtained using the adiabatic nuclei approximation and a non-adiabatic model. Non-adiabatic effects are significant for the v=0 to 1 cross section (and dominate the small v=0 to 2 result). Some early calculations at the equilibrium geometry (R=2.068 a0) have been corrected.