Scavenger and time dependences of radicals and molecular products in the electron radiolysis of water : examination of experiments and models

Laplace transform techniques have been used to compare the scavenger and the time dependences of e{sub aq}{sup {minus}}, OH, H{sub 2}, and H{sub 2}O{sub 2} produced following the electron radiolysis of water. A new empirical relationship for the variation of these yields on scavenger concentration is presented. Experimental data on the scavenging of e{sub aq}{sup {minus}}, OH, H{sub 2}, and H{sub 2}O{sub 2} have been fitted with the new function, and it is found that the inverse Laplace transform of the results for e{sub ag}{sup {minus}} and OH do not match the direct experimental measurements of the time dependences of these species. There is no apparent reason for this discrepancy. The accuracy of Laplace transform techniques in nonhomogeneous kinetics was determined by using a deterministic diffusion-kinetic model to calculate the time dependences of the yields of these species in pure water and the dependence of their yields on the concentration of a few selected scavengers. Numerical Laplace transforms of the time dependences of e{sub aq}{sup {minus}}, OH, H{sub 2}, and H{sub 2}O{sub 2} reproduced well the calculated scavenger concentration dependences. The inverse Laplace transform of the new function accurately reproduced the predicted time-dependent kinetics of diffusion-kinetic models even when verymore » different initial distributions of e{sub ag}{sup {minus}} were used. This function is shown to be an improvement on previous functions, especially at matching the yields at high scavenger concentrations. The parameters derived in the analysis of the available experimental data can be used with the new function or its Laplace transform to easily determine the scavenger concentration dependence or time dependence of any of these species with other scavengers for which the scavenging rate constant is known. The influences of various parameters used in the diffusion-kinetic modeling of the radiation chemistry of water are discussed.« less