Comparison of Photon Stimulated Dissociation of Gas Phase, Solid, and Chemisorbed Water.
GEORGE WASHINGTON UNIV WASHINGTON D C DEPT OF CHEMISTRY
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Recent electron-and-photon-stimulated desorption ESDPSD data for H20 in the condensed phase and chemisorbed on GaAs110 and Ti001 are interpreted utilizing previously published photoelectron, electron coincidence and Auger data along with theoretical calculations. Comparison with fragmentation data from the gas phase indicates that only two hole-one electron type states are effective for desorption in condensed or molecularly chemisorbed hydrogen bonded water. The 1bsub2-1 excitation, which effectively dissociates H20 gas via predissociation, is ineffective in the condensed phase because of the presence of intermolecular decay mechanisms which compete with the predissociation process. Hydrogen bonding reduces the effectiveness of the 2asub2-1 excitation for H desorption. The 1bsub1-1 4asub1 two hole-one electron states are sufficiently long lived occupation of the strongly antiboding 4a orbital also makes them repulsive. These properties make the two hole-one electron states the most persistent for H desorption from the H20 phase studied. The core level PSD spectrum from solid D20 is also interpreted. All of the results are found to be comparable to previously reported results for CO.
- Physical Chemistry