The Yields of Free H and OH in the Irradiation of Water

Abstract

Quantitative information on radiation chemistry of water solutions has been appearing in considerable amount in recent years. One impetus to this work is the hope that from these data can be deduced values of the number of free radicals and molecules of different kinds formed from the decomposition of water by various kinds of radiation. These numbers could then be used to test proposed theories of the chemical actions of radiation. The present paper is an attempt to put together the data that appear to bear most cogently on this subject. Only those reactions are included which have been studied comprehensively enough to yield a consistent and detailed interpretation; no doubt, some significant information has been overlooked. The indirect action of radiation on solutes is generally ascribed to formation of chemically reactive free radicals, H and OH, by radiation decomposition of the water. In addition, the molecular water decomposition products H2 and H202 always appear, in a yield which diminishes as the ion density of the radiation decreases. The yields of these four products should be deducible from the yields of various reactions brought about by irradiation of solutions. It has frequently been assumed (1-5) that the two kinds of free radicals occur in approximately equal amounts, so that the chemical action of radiations on water could be represented by the two equations