Electron Paramagnetic Resonance Studies of the Radiolysis of H2O in the Solid State

Abstract

Free radicals formed by electron irradiation of H₂O at 77°K have been studied with the electron paramagnetic resonance (EPR) technique. In particular the spectrum of the OH radical is identified in irradiated CaSO₄·2H₂O and LiSO₄·H₂O and in irradiated hexagonal ice. The effective spin Hamiltonian is determined for OH in these crystals. For the ice case, the experimentally determined spectroscopic splitting tensor is shown to be in agreement with a simple theory based on crystal‐field theory. The experimentally determined hyperfine splitting of the OH radical is shown to be in agreement with that predicted by an LCAO MO calculation and verified by an EPR study of OH produced by microwave discharges in gases. In the irradiated sulfates magnetic resonance signals from OH, H atoms, and some form of trapped electron were observed. Radiation‐yield measurements for OH in ice at 77°K are given for the dose range 10⁴ to 10⁹ rad.