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 vs. 2.4 nm). These observations suggest that, even at this high ionization energy, autoionization of water competes with direct ionization. (C) 2004 Elsevier B.V. All rights reserved.