Integral rate constant measurements of the reaction H +D2O → HD(v′, j′)+OD

ion has been found not to occur in the D + H20 reaction.22 Recently, the back reaction OH+D2 -HOD +D has been studied,12 and the HOD product shows pronounced back scattering, which is consistent with the proposed transition-state geometry. In addition to these investigations, two groups have reported experimental studies of the effect of vibrational excitation on the abstraction reaction. Crim and coworkers28,29 have studied the reactions of thermal H atoms with H20 and HOD possessing several quanta of vibrational energy. Zare and co-workers24,25 have studied the reactions of hot H atoms with HOD and D20 containing one or two quanta of vibrational energy. These studies have attracted considerable attention because they provide the first examples of bond-specific and mode-selective bimolecular reactions. Corresponding theoretical caicuiations30-33 have been carried out in an effort to account for the observed reaction cross-section enhancements, OH/OD branching ratio changes, and hydroxyl radical energy disposal arising from vibrational excitation of the water reagent. In none of the experimental studies mentioned above has observation of the molecular hydrogen coproduct of the abstraction reaction been reported. It is expected that as the "new bond" the molecular hydrogen should receive a greater fraction of the available energy as internal energy than has been observed for the hydroxyl, "old bond." This prediction is supported by the original QCT ca1culationsof Schatz and co-workers 18 for the H + H20 reaction. In this paper we report measurements of the HD product internalstate distributions for the reaction H+D20 at a relative collision energy (Erel ) of approximately 2.7 eV; this energy is well above the 0.94 eV (Ref. 34) reaction barrier and far exceeds the reaction's endothermicity (0.66 eV). These results are briefly compared with the QCT calculations of Kudla and Schatz (see the accompanying paper for a more detailed comparison).35 We find that the HD coproduct is both rotationally and vibrationally excited; specifically, approximately 35% of the total energy is partitioned into internal energy of the HD coproduct. In addition, we find that the fraction of available energy partitioned into HD rotation is independent of the HD vibrational state. Excellent qualitative agreement appears to hold between theory and experiment.