Inelastic-collision cross sections for the interactions of totally stripped H, He and C ions with liquid water

Abstract

The HKS and CDW-EIS models are implemented to determine single ionization cross sections (SICS) corresponding to the impact of H +, He 2+ and C 6+ ions on liquid water, for incident energies from 0.3 to 10 MeV/u. Corrected expressions for the HKS method have been used. The same kind of initial electron wave functions and binding energies have been used with both methods, in order to compare the formalisms themselves. Double and single differential as well as total SICS of liquid water have been calculated by use of both formalisms and comparisons have been made between their theoretical predictions. Also, these results have been compared with experimental values reported previously for ionization of water vapor due to protons and alpha particles. Despite its sophistication, the CDW-EIS method does not show better results than the more simple HKS model when comparing liquid water single and double differential cross sections with experimental water vapor values. However, once the excitation cross sections are included to determine electronic stopping cross sections in liquid water, the results based on the CDW-EIS method provide the best agreement when compared with corresponding data published in ICRU reports, obtaining discrepancies of about 9%, 16% and 19% for incident protons, alpha particles and carbon ions respectively.