Figure 4

Plots of the concentration of \(\hbox {H}_2\) at the water-gas boundary at equilibrium, as a function of the thickness of water layer for various dose rates for Spinks and Woods [left], and Kreipl et al. [right]. The black crosses show the data points gathered from the simulations, and the gradient triangle in the bottom right shows that for gamma radiation, the quadratic dependence between yield of \(\hbox {H}_2\) at equilibrium and water thickness L does not hold universally. Reaction rate coefficients for the zeroth order reactions used to simulate the constant input of chemical species as a result of irradiation in the physical stage were taken from the G-values from: Table 7.4 in Spinks and Woods⁵³ using ‘\(\gamma\) and electron radiation with 0.1–20 MeV energies, pH 3–11’ for the left figure, and Table 5 in Kreipl et al.²⁰ using the bottom row for the right figure. Diffusion coefficients, reaction network and reaction rates are taken from Tables 2 and 3 in Kreipl et al.²⁰, respectively.