Accession Number : ADA134986

Title :   Comparison of Photon Stimulated Dissociation of Gas Phase, Solid, and Chemisorbed Water.

Descriptive Note : Technical rept.,


Personal Author(s) : Ramaker,D E

PDF Url : ADA134986

Report Date : Sep 1983

Pagination or Media Count : 26

Abstract : Recent electron-and-photon-stimulated desorption (ESD/PSD) data for H20 in the condensed phase and chemisorbed on GaAs(110) and Ti(001) 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 1b(sub2)-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 2a(sub2)-1 excitation for H+ desorption. The 1b(sub1)-1 4a(sub1) 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.

Descriptors :   *Water chemistry, *Photodissociation, Gallium arsenides, Substrates, Photochemical reactions, Phase studies, Gases, Solid phases, Chemisorption

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE