Ionization and excitation yields in liquid water due to the primary irradiation: Relationship of radiolysis with far UV-photolysis

Abstract

First collision yields of ionization and dissociation in liquid water, due to incident electrons of energy 500 eV to 1 MeV, have been calculated in the optical approximation by using the experimental dipole oscillator strength distribution (DOSD) and the recently determined photoionization and photodissociation quantum efficiencies in the far UV. From these the G value of ionization for the complete absorption of these radiations is estimated employing a heuristic method based on energy balance. It is found that ca. 25% of total ionization and <5% of total dissociation originate from primary interactions alone; the rest are due to the action of the secondary electrons. Incorporation of dissociative electron attachment (DEA) is necessary to account for the total radiolytic dissociation yield. A new definition of ionization potential in liquid water is provided depending on the mechanism and a tentative value of 11.7 eV is assigned to it.