Large angle elastic scattering from molecules: Vibrational Compton-like scattering

Abstract
The band shape for the electron impact excitation of vibronic levels in molecules is investigated as a function of momentum transfer by use of the first Born approximation of scattering theory. The unresolved vibronic band, including translational excitation, for excitations which leave the molecule in its ground electronic state are reduced to a vibration-rotation (VR) generalized oscillator strength (GOS) and sum rules for it are reviewed. The shape of the VR–GOS is investigated as a function of momentum transfer. Assuming simple harmonic motion, the band shape is found to behave in a manner similar to the Compton peak in electron ionizing collisions although only discrete transitions are considered. At sufficiently high momentum transfer for certain molecules, the 0→1 vibrational excitation is no longer found to be the most probable.