Convergence of the separable exchange approximation in electron-molecule scattering using Slater-type basis sets

Abstract

The convergence of a finite L2 expansion of the exchange interaction is studied in the single-centre close-coupling formulation of electron-molecule scattering at the static exchange level. It satisfies no variational principle; some confusion about the convergence process may have resulted in the past from the emphasis given to a diagonal representation of the exchange operator. A number of expansion sets are tested, which include short-range multicentre molecular orbitals derived from Slater-type atomic basis sets and long-range one-centre numerical orbitals. An expansion set optimising the rate of convergence is derived. Illustrative results are presented for e-H2 and e-N2 scattering and compared with previous calculations in order to assess the accuracy of the method and its range of applicability.