Femtosecond Studies of Electron-cation Dynamics in Neat Water: the Effects of Isotope Substitution

Femtosecond photoionization studies in neat protio and deuterio water at room temperature have been performed. The rate of appearance of the solvated electron is slower in D,O than in H,O, consistent with the predictions of continuum theories. The observed geminate recombination dynamics of the cation-electron pair is also isotope dependent. The recombination time is slower in D20 and the fraction of solvated electrons that escape recombination is greater in D20 than in H20. After 165 ps, 54 k I% ( i one standard deviation) of the solvated electrons escape geminate recombination in H,O and 62i 1% escape in D,O. The increased electron escape yield is attributed to an energy transfer effect on the electron thermalization distance.