Isotopic effects in the angular dependence of the energy loss and angular distribution of protons and deuterons in Al foils at low energies

Abstract

Energy loss and straggling has been measured for hydrogen and deuterium ions in thin solid aluminum foils in the low-energy range $E<10\mathrm{keV}$ and in the forward direction, both as a function of the energy, and at fixed energies as a function of the observation angle. Whereas no isotopic effect in the energy loss at the forward direction was observed, significant differences appeared when observing at nonzero angles. Monte Carlo simulations and model calculations of the energy loss as a function of the observation angle using a frictional-type energy loss, taking into account the path-length enlargement, the elastic energy loss, and the foil roughness, led to an understanding of the main physical features at these energies. The observed isotopic effect at nonzero angles can be fully accounted for by differences in the foil roughness influence and in the elastic energy loss.