Exchange approximations in the scattering of slow electrons by polyatomic molecules

Abstract

The Hara (1967) and asymptotically adjusted versions of the free-electron-gas exchange (FEGE) approximation are compared with the orthogonalisation technique for electron scattering by CH4 and H2O. In general both FEGE approximations are more attractive than the orthogonalisation approximation but there is evidence that the asymptotically adjusted version overestimates the exchange effects at low scattering energies.