Some calculated quantities in the radiation chemistry of molecular hydrogen: average energy per ion pair and numbers of singlet and triplet excitations per ion pair

The average energy (W) expended per ion pair (ip) in hydrogen and the numbers of molecular singlet (R2) and triplet (R3) excitations per ion pair were calculated for electrons of up to 1500 eV energy and extrapolated to high energy limits. Experimental and theoretical cross sections were used. Calculations were made for a secondary electron energy distribution based on measurements of Opal, Beaty, and Peterson at 500 eV and for the Gryzinski distribution. For each distribution calculations were made for two assumptions concerning dissociative ionization. For the preferred calculation (experiment-based secondary electron distribution for ordinary ionization and zero kinetic energy for electrons formed in dissociative ionization) the results at high energies are W = 36.8 eV/ip, R2 = 1.06 (includes dissociative excitation), and R3 = 0.359. The experimental value of W is 36.3 eV/ip.