THE SEPARABLE REPRESENTATION OF EXCHANGE IN ELECTRON-MOLECULE SCATTERING .1. ELASTIC-SCATTERING AND ROTATIONAL-EXCITATION

We have investigated a systematic procedure for representing, as a sep arable expansion, the exchange interaction in electron-molecule scatte ring. Illustrative calculations of scattering quantities (eigenphase s ums, total cross sections and rotationally-resolved differential cross sections) have been performed for electron scattering from molecular hydrogen in the fixed-nuclear-orientation approximation. The exchange basis can be constructed from the same Cartesian Gaussian functions us ed to generate the near-Hartree-Fock static interaction, supplemented by an even-tempered series of Gaussian functions located on the molecu lar centre of mass. Particular emphasis is placed on examining the con vergence properties of this series.