Calculated excitation and ionization yields and fluctuations in irradiated water in the liquid and vapor phases

Two Monte Carlo computer codes developed independently at ORNL and GSF have been used to compute the slowing down of electrons in water in the liquid and vapor phases. Calculated excitation and ionization yields for the two phases are compared. The distributions in the number of ionizations produced by electrons of various initial energies are presented. Fluctuations in the ionization yields from different shells are expressed by the corresponding Fano factors. The Fano factor for total ionization is about 0.15 for elecrons of energies ≥ 200 eV in the liquid compared with about 0.25 in the vapor