RADICAL GENERATION UPON GAMMA-IRRADIATION OF 2 AMORPHOUS AND 2 CRYSTALLINE FORMS OF WATER AT 77 K

The effects of gamma-irradiation at 77 K on two crystalline forms of w ater, namely, cubic and hexagonal ice, and on two amorphous forms of w ater, made by hyperquenching of liquid water or deposition of water va pors, have been studied by electron spin resonance (ESR) spectroscopy. Mainly OH radicals are formed from cubic ice directly made from liqui d water. In contrast, comparable amounts of OH and HO2 radicals are fo rmed on irradiation of cubic ice made by heating glassy water, and the ir relative yields depend strongly on the irradiation dose. Comparable yields of OH and HO2 radicals were observed on gamma-irradiation of t he two amorphous solids, and their ratio did not depend on irradiation dose. The formation of HO2 radicals is attributed to the presence of shallow proton traps, or Bjerrum-like L-defects, in the two amorphous solids and in disordered regions of cubic ice.