Lineshape analysis of keV electrons scattered from hydrogen molecules

Accurate measurements of keV electrons scattered elastically from H₂ molecules reveal a lineshape that is an intrinsic property of the target. The intrinsic width of the elastic peak is due to the non-zero momentum of a proton bound to a molecule. A more precise analysis of the lineshape shows that it deviates from Gaussian. This deviation is shown to be a consequence of the dominance of the momentum component of the protons along the molecular axis. The mean-kinetic energy of the protons in H₂ obtained based on the new peak shape agrees better with theory than the one obtained based on a Gaussian peak shape. These measurements demonstrate the possibility of a new way to study the dynamics of nuclei by electron scattering.