Inter-track radical recombination rates at FLASH dose rates

Determine the yields of hydroperoxyl, peroxyl and organic radicals, and of hydrogen peroxide, as a function of instantaneous dose rate from $100\ \text{to}\ 10^{9}\,\mathrm{rad}/\mathrm{s}$ in oxygenated aqueous and lipid-containing media, including inter-track overlap. Required inputs: second-order rate constants, radical diffusion lengths and the spatial density of tracks at a given dose per pulse. An answer is measured and computed yield curves $G(\text{dose rate})$ accurate to about 10 percent.

Pulse-radiolysis and chemical-probe measurements of radical and peroxide yields spanning the dose-rate range, matched by stochastic track-chemistry simulation.