Radiation-induced formation and stabilization of ionic species in organic low-temperature glasses

Abstract

In organic low-temperature glasses the efficiency of recombination reactions is lower than in the same compounds in the liquid state. A considerable part of the primary radiation-generated charge carriers can be stabilized in physical traps of the matrix or by chemical attachment reactions to added charge scavengers. As a rule fast- and slow-formation components depending on the different charge migration processes through the matrix (tunneling, hopping or hindered diffusion of molecular species) can be observed. From the intensity and the decay kinetics of the optical absorption bands the efficiency of solute ion formation and of the stabilization of these ions in a given matrix may be evaluated. Experimental results obtained by steady-state and pulse-radiolysis experiments for styrene (St) and 1-methylstyrene (MSt) ions in neutral glasses (methylcyclohexane, squalane) with added external charge scavengers (BuCl, CCl 4, triethylamine) and in glasses with internal charge-scavenging properties (BuCl, MTHF) are analyzed and discussed in this paper. It is shown that the formation and decay reactions depend in a complicated manner on the matrix viscosity (changed by temperature and matrix composition variation), the scavenging properties of the matrix (changed by the kind and composition of the matrix) and the solute concentration.