Initial Radial Distribution of Excited States Produced by Delta-Rays Ejected by a 300 keV Proton in Water Vapor

A microscopic approach based upon the assignment of electron impact cross sections has been used by Green et al. (1) to calculate the efficiencies for degradation of low energy electrons in water. By Monte-Carlo techniques Berger (2) has calculated the spatial distribution of the total energy deposited by δ-rays ejected at various energies and at various angles with respect to a heavy ion beam. In the present work we develop a model which combines these two results to calculate the energy per unit volume deposited in various excitations of the H₂ O molecule by δ-rays ejected by a 300 keV proton. Results are presented for vibrational excitations, electronic excitations, and ionization continua as a function of the radial distance from the proton beam.