ENERGY DISPOSAL IN THE VIBRATIONAL-STATE- AND BOND-SELECTED REACTION OF WATER WITH HYDROGEN-ATOMS

The measured OH product state distribution from the reaction of vibrationally excited water with thermal hydrogen atoms supports an intuitive picture of selective energy disposal in this reaction. Excitation of the third overtone of the O-H stretch (4-nu-OH) in either water or HOD provides enough energy to initiate the reaction, and laser-induced fluorescence (LIF) monitors the state populations of the reaction product OH or OD. The internal energy of the detected product is small compared to the roughly 9000 cm-1 of available energy. The average rotational and vibrational energies of OH produced from reaction of H2O(4-nu-OH) are 320 +/- 10 and 100 +/- 30 cm-1. The reaction of HOD(4-nu-OH) produces OD with average rotational and vibrational energies of 190 +/- 10 and 440 +/- 90 cm-1. Analysis of Doppler profiles in the LIF excitation spectra shows that the energy in relative translation of the products is no more than 5000 cm-1, leaving the substantial balance of available energy in the H-2 product, most likely as vibrational excitation.