Electron Compton defect observed in He, H2, D2, N2, and Ne profiles: a reevaluation of the binary encounter theory

A high energy electron impact spectroscopy (HEEIS) apparatus has been constructed to undertake high precision Compton scattering experiments. Electron Compton scattering experiments are performed by crossing a beam of high energy, but non-relativistic, electrons with a beam of atoms or molecules and measuring the energy loss spectrum over a range of scattering angles. The improvements of design and technique, the method of data analysis, and the theory used to convert cross-sections to Compton profiles are discussed fully. It was found that the energy loss spectra taken over a range of scattering angles do not reduce by means of the Binary Encounter approximation (impulse approximation) to Compton profiles in agreement with theory. The disagreement is most apparent in a shift of the experimental Compton peak the- Compton defect - from the peak predicted by the Binary Encounter theory. The Compton defect has been studied in detail for momentum transfers from 1.5 to 12 a.u. for both He and H2. Defect measurements for D2, N2, and Ne have also been made and it was found that the N2 and Ne defects were opposite in direction from the He and H2 defects. The D2 defect was identical to the H2 measurement