A new estimate of the ⋅OH radical yield at early times in the radiolysis of liquid water

We have revisited earlier experiments on pulse radiolysis of aqueous solutions carried out at very high dose rates (intensities) up to 5×1027 eV g−1 s−1 (∼1012 Gy s−1). The ⋅OH radical yield G⋅OH=4.6±0.25 molec./100 eV, derived from those studies, is here estimated to correspond to the time scale of ∼100 ps where, under these high irradiation-intensity conditions, spur overlap is assumed to be total. This ∼100 ps estimate is obtained with the aid of Monte Carlo simulation results of the nonhomogeneous chemical stage of water radiolysis. It is found that such a G⋅OH value at ∼100 ps compares well with the ⋅OH yield values inferred from inverse Laplace transform analyses of ⋅OH scavenger data and from Monte Carlo calculations, but strongly disagrees with direct measurements of G⋅OH (5.9±0.2 molec./100 eV at 200 ps).