Gaussian ranges and energy straggling in gases

Energy and range fluctuations are obtained for Gaussian (long path length) distributions in several gases for incident protons and alpha particles over a substantial range of energy loss and incident energy. The calculations are based on Fano's equation for the mean square energy loss per unit path length and utilize accurate straggling and stopping-power parameters principally determined by Zeiss, Meath, MacDonald, and Dawson from dipole oscillator-strength distributions. The results are compared with experimental data on energy straggling of 2 to 4 MeV alpha particles in helium, and further experiments are suggested. 17 references