Electron scattering from diatomic molecules in the first Born approximation

The differential cross sections for electron scattering from the diatomic molecules H2 and N2 in the first Born approximation, using molecular wavefunctions, have been calculated. The molecular wavefunctions for H2 and N2 were in the form of a Slater determinant(s) with one-electron Slater-type orbitals (STO's). For the purpose of simplifying the calculation the STO's involved in all two-center, but not one-center, integrals were expanded in Gaussian-type orbitals (GTO's). The result of the calculation for H2, using a configuration interaction (CI) wavefunction containing 97% of the binding energy, leads to agreement with existing experimental data. The calculated scattered intensity for H2 can be considered as the most accurate one for comparison with experiment at the 1% accuracy level. This accuracy is a result of the approximate wavefunction containing 1% less energy than the total experimental energy. For the case of N2 the double ξ exponent wavefunction of Richardson was used. It was found that the scattered intensity of the electron-nuclear bonding charge density is very sensitive to the choice of molecular wavefunction used. This study represents the most definitive calculation of the two-electron effects in total scattered intensity so far reported. The total result, including both one- and two-electron terms, was found to be in qualitative agreement with experiment.