  The picosecond geminate recombination kinetics for hydrated electrons
generated by 200 nm two photon absorption (12.4 eV total energy) has been
measured in both light and heavy water. The geminate kinetics are observed to
be almost identical in both H2O and D2O. Kinetic analysis based upon the
independent reaction time approximation indicates that the average separation
between the electron and its geminate partners in D2O is 13% narrower than in
H2O (2.1 nm vs. 2.4 nm). These observations suggest that, even at this high
ionization energy, autoionization of water competes with direct ionization.
