Radiolysis of compounds in solution. Model calculations on the effects of concentration, impurity, and dose rate

The kinetic behavior of compounds subjected to radiolysis in solution has been investigated for a generalized mechanism that comprises an infinite number of consecutive reactions between the radiolysis products and radicals (Z.) derived from the solvent. When steady-state conditions for these primary radicals exist, it is rigorously shown that the dose, D/sub x/, required to convert any desired fraction x of the original solute A1 into products varies linearly with the initial A1 concentration, A0, regardless of the number of steps in the process and independently of whether or not A1 decreases exponentially with dose. Furthermore, it is demonstrated that the slope of the linear plot measures the reactivity of A1 and all products derived therefrom with (Z.), while the intercept measures the reactivity of (Z.) with solute-independent impurities that may be present. The kinetic behavior of the system is independent of dose rate when only consecutive steps are involved in the radiolysis mechanism. The characteristics of radiolysis mechanisms that involve reaction of the solute with secondary products of the radiolysis have also been investigated. Such mechanisms do not, in general, yield linear plots of D/sub x/ vs A0. The deviation from linearity are, in fact, a measure of the reactions of solute with secondary products. Model calculations also show that the kinetic behavior of such systems depends on the dose rate. This dependence can, under the proper conditions, become manifest at much lower dose rates than that due to reactions of primary and secondary intermediates with one another