Ratio of Cross Sections for Electron Capture and Electron Loss by Proton Beams in Metals

Measurements have been made of the ratio of the charged to the neutral component (protons to hydrogen atoms) in hydrogen ion beams of energies between 20 and 400 kv, passing through the metallic media beryllium, aluminum, silver, and gold. The data show that this ratio is the same, within the accuracy of the experiment, for the three lighter elements, but is slightly less in gold above 100 kv. The curves depicting this ratio as a function of ion speed cannot be fitted by a power law over the entire energy range, but the high energy end of the data can be fitted fairly well in this way. At 350 kv, the slopes correspond to a dependence on ion speed $v$ of the form $v^9$ in the case of the lighter elements, and $v^7$ in the case of gold.