Frequency Distributions of Energy Deposition by Fast Charged Particles in Very Small Pathlengths

The frequency distribution of energy losses in an equimolar mixture of He-CO₂ by 46.4-MeV protons has been examined experimentally and compared with the distributions predicted by the Blunck-Leisegang-corrected Vavilov theory. The distributions studied correspond to mean energy losses of 1.56, 7.85, and 15.6 keV. The theoretical predictions of the distributions with the larger mean energy losses agree well with the experimental data in the region about the most probable energy loss. However, agreement between the values of the measured and predicted full widths at half-maximum of the distribution found for a mean energy loss of 1.56 keV is not as good as for the other distributions. This is due partly to a larger uncertainty in the experimental parameters of the calculation. Considerable disagreement exists when theory and experiment are compared in regions of high and low energy losses for all of the distributions.