On the ejection of hydrogen ions from organic solids impacted by MeV ions

In the ejection of material from organic solids following MeV ion bombardment, the initial velocities of the ejected species contain information on their interaction at the surface of the solid and the selvedge. Here, experimental data are presented on the sample thickness dependence of yield (the number of secondary ions per incoming ion) and the initial radial velocity distribution of singly charged hydrogen ions (H+, H2+, H3+, H-) and other low-mass fragments ejected from organic solids of nitrocellulose and arachidic acid due to the impact of 72.3 MeV 127I14+ ions. An increase is observed in the width of the radial velocity distribution of the positive hydrogen ions as the thickness of the nitrocellulose film is increased. The results are in qualitative agreement with simulations based on Coulomb repulsion from the charged track created by the incident ion. (orig.)