Lyoluminescence dosimetry part I. Principles

Abstract

The first part of the paper deals with the basic processes, physical and chemical, underlying the phenomenon of lyoluminescence (LL) of irradiated materials particularly suited to radiation dosimetry. Tracing the history of the subject, the paper explains the general characteristics of lyoluminescence of organic compounds and outlines the range of materials suitable as LL phosphors. The effect in organic solids is a consequence of reactions of radiation-induced free radicals, which in solution are free to react. The Russell-Vassil'ev scheme of reactions of secondary peroxy radicals is apparently involved in the lyoluminescence of substances dissolved in pure water. In solutions of chemiluminescent sentizers, like luminol or lucigenin, radicals initiate a sequence of processes leading to intensely luminescent reactions, thus enchancing the LL yield. Another technique of increasing the sensitivity of dosimetry based on lyoluminescence is based on the energy transfer to intensely luminescent dyes, ions or complexes added to the solution. LL dosimetry employing inorganic phosphors (alkali halides) depends on a different physical mechanism i.e. on the formation of electron and hole defects in the crystal, and the subsequent reactions of electron and hole products near the surface of dissolving material. In pure water both F- and V2-centres are needed, but in solutions of certain sensitizers (luminol, fluorescent dyes, thallous chloride) only F-centres are required. Part I gives examples of dose-LL yield relationships for typical materials, both organic and inorganic, and deals with the environmental effect on the storage and read-out of dosimeters.