Effects of pulse dose on hydrated electron decay kinetics in the pulse radiolysis of water. A computer modeling study

Results from a computer simulation of the pulse radiolysis of water using an improved spur model which includes a novel hydrated electron distribution and a spur overlap approximation are reported. Data for hydrated electron decay at nanosecond and subnanosecond times following pulse radiolysis of air-free water are fit within experimental error by adjustments in the initial spatial distribution of spur intermediates and the energy deposited per average spur. Using the same parameters which are successful in modeling the hydrated electron decay kinetics, pulse radiolysis data for hydroxyl radical decay are also fit within experimental error. Again using the same model parameters, the hydrated electron decay data for variable pulse dose were computed for times from 10/sup -12/ to 10/sup -6/s following the pulse. At a pulse dose of about 8000 rd the fit between computations and experimental data for hydrated electron concentration is within experimental error at all times from 100 ps to 1 ..mu..s. At several kilorad pulse doses there is qualitative agreement but at very low pulse doses (below 200 rd) the fit between computer predictions and experimental hydrated electron decay data is not even qualitatively similar at times longer than 10/sup -7/s. The pulse-dose dependent deviations frommore » our computer model predictions can be reconciled using Mozumder and Magee's blobs and/or short tracks. The average spur density of these spatial regions is postulated to be on the order of that present in 8000-rd pulse-irradiated water. 5 figures.« less