Influence of translational motion of rare gas atoms on electron-atom Compton scattering

We report an atomic momentum spectroscopy study about how translational motion of gaseous targets affects electron-atom Compton scattering. A series of experiments on rare gas atoms in an effusive beam reveals that forward-backward asymmetry exists in energy loss for He with respect to the target beam direction, but its degree rapidly decreases for heavier atoms. Furthermore, it is shown that the results are reproduced by a gas beam model and supported by a reference experiment on He in a gas cell. We believe the present work forms a basis toward investigating intramolecular atomic motion.