Concentration dependent effects in low temperature radioluminescence of aqueous ionic systems

Abstract

Radioluminescence of aqueous solutions of concentrated alkaline metal chlorides and alkaline ices was investigated by μs-pulse radiolysis at temperatures 6–77 K. The influence of the electrolyte concentration was examined in respect to the pattern of emission spectra , rate of their decay and the total output of spontaneous luminescence observed in the wavelength range 280–700 nm. The results clearly indicate that the structure of electron traps involved in the radiative recombination [( e − vis ) Me + , ( e − ir ) Me + ] depends not only on the nature of cation Me + and anion (Cl − , OH − ) but also on their concentration. Dependencies of the integrated luminescence intensity on the solute concentration in glassy chloride and alkaline ices are quite different. The luminescence decreases with growing concentration of chlorides in the range 7–14 M but increases for alkaline glass in the same concentration range. Time resolved studies of radioluminescence carried out by μs-pulse radiolysis in the temperature range 6–77 K seem to confirm the existence of charge-transfer complexes CTTS* for Cl − ions. These results can be related to the absorption measurements in the fs–ps time scale carried out for similar systems at room temperature by Gauduel et al. (1995) .