Energy-loss distributions of 50-250-keV protons traversing thin solid foils: Determination of the skewness coefficient and influence of foil roughness.

Abstract

From new measurements of energy-loss distributions of proton beams in thin solid foils we determine the second- and third-order moments of the energy spectra, and evaluate the skewness coefficient \ensuremath{\gamma}, which is of interest in studying the asymmetry of the energy-loss spectra. We present calculations of \ensuremath{\gamma} based on electron gas and Thomas-Fermi models; we compare these calculations with the experimental results and with the values derived from Bohr's energy-loss treatment. We present a theoretical analysis of the effects of surface roughness on the skewness of the energy-loss distributions.