FREE-ION YIELD IN LIQUID ARGON INDUCED BY AM-241-ALPHA IRRADIATION

Recent measurement of free-ion yield in liquid argon by Gruhn and Edmiston [Phys. Rev. Lett. 40, 407 (1978)] using Am241-± irradiation has been analyzed using a track model. Because of dense ionization, recombination dominates in the core giving insignificant free ions. In the time scale of observation, the rays mostly degenerate into ion pairs to which the Onsager probability is applicable. The electron thermalization distance is found to be 232 nm, the same as for radiolysis and in agreement with Freeman (Phys. Rev. B, preceding Comment). Secondary electrons at energy about 200 eV can effectively penetrate the core. © 1979 The American Physical Society.