Energy Migration and Localization Processes in γ-Irradiated, Amorphous n-Alkyl Disulfides

Abstract

It was previously determined that amorphous alkyl disulfides irradiated at 77°K contain ionic species, alkyl radical species, and RS· radical species. The current study has been undertaken in order to determine the relative amounts of these species as a function of alkyl chain length in an effort to understand more clearly the energy migration and localization processes which occur in these compounds. It was found that no significant dependence of alkyl chain length (from methyl disulfide through eicosyl disulfide) occurs for the yield of ion pairs formed as a result of charge migration to the sulfur. This study indicates that essentially all free charge created in these compounds as a result of exposure to ionizing radiation migrates to and localizes at the disulfide group. From examination of the alkyl and RS· radical yields in these compounds as a function of chain length, it appears that excitation also localizes at the disulfide group. However, the localization of excitation at the sulfur group occurs less readily than does charge localization. Models concerning possible mechanisms for localization of excitation are discussed. Utilizing the models presented, the results of this study indicate that the probability for localization of excitation at the disulfide group is about seven times greater than that for localization of excitation at any CH₂ group.