Inelastic high-energy electron scattering from a hydrogen molecule. I. X–B and X–E transitions

Abstract

Generalized oscillator strengths have been computed for high-energy electron scattering by H2. The optically allowed transitions from the electronic ground state (X 1Σ+g) to the B 1Σ+u state and the optically forbidden transitions to the E 1Σ+g state have been considered. Accurate wave functions expanded in explicitly correlated Gaussian functions were used to describe the electronic states of H2. The dependencies of the form factors on the molecular orientation, the momentum transfer, and the internuclear separation are discussed. For the X–B transitions the form factors have been integrated over the internuclear separation with accurate vibrational wave functions. A comparison of the obtained values with those computed assuming the Franck–Condon approximation has shown that the latter are not always reliable. In the region of a very small momentum transfer, the present results are found to be very close to the accurate values obtained for optical transition probabilities to the B state with wave functions depending explicitly on odd and even powers of the interelectronic distance.