Damage and Energy Deposition in RNase by Low-Energy Ions

Model calculations are made of the cross sections for inactivation of RNase by low-energy ions (0.2-5 keV for protons). In comparing to experiments, in which the particles are often stopped in the material, the calculated inactivation cross sections are averaged over the energy degradation process. A continuous-slowing-down model is constructed that includes, to first order, angular deflections and secondary ions. Comparison is made between different cross section and stopping power descriptions throughout the region where energy transfer to the nuclei, through elastic collisions, and energy transfer to the electrons are both important. It is shown that the model employed is useful for making preliminary comparisons with experimental data at low energies. The present calculations appear to account for the principle features of the energy dependence of the inactivation cross section for incident helium ions but not for incident protons.