Temperature Dependence of Excited‐State Proton Transfer and Geminate Recombination Processes in Water and in Glycerol‐Doped Ice

Abstract

AbstractThe reversible proton dissociation and geminate recombination of photoacids was studied as a function of temperature in neat water, binary water mixture containing 0.6 mol% glycerol, and doped ice containing 0.6 mol% glycerol. The deuterium isotope effect on both condensed phases was also studied. 8‐hydroxypyrene‐1,3,6 trisulfonate trisodium salt was used as the electronically‐excited‐state proton emitter. The experimental data are analyzed by the Debye–Smoluchowski equation solved numerically with boundary conditions to account for the reversibility of the reaction. We propose a qualitative model to describe the unusual temperature dependence of the proton transfer rate in the liquid phase. We also propose a model for proton transfer in solid ice based on L‐defects transport as proton acceptors. While in the liquid phase at t > 10°C the proton dissociation rate constant is almost temperature independent, in glycerol‐doped ice we find a large temperature dependence.