MECHANISTIC STUDIES OF THE PHOTODISSOCIATION OF PHYSISORBED O-2 GRAPHITE/

Citation
Ra. Bennett et al., MECHANISTIC STUDIES OF THE PHOTODISSOCIATION OF PHYSISORBED O-2 GRAPHITE/, Journal of physics. Condensed matter, 6(10), 1994, pp. 1955-1964
Citations number
20
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
09538984
Volume
6
Issue
10
Year of publication
1994
Pages
1955 - 1964
Database
ISI
SICI code
0953-8984(1994)6:10<1955:MSOTPO>2.0.ZU;2-V
Abstract
We have investigated the vacuum ultra-violet photodissociation of mole cular O2 physisorbed on graphite using synchrotron radiation with phot on energies in the range 13-35 eV. The yield of desorbed O+ ions shows a threshold at approximately 19.5 eV and resonances at 24.5 eV and 28 .5 eV, contrasting strongly with the gas phase photodissociation cross section. The principal mechanism of O+ production appears to be dipol ar dissociation driven by photoelectrons generated in the substrate. A n enhancement in the detection efficiency of low-energy ions, compared with previous measurements, has identified an additional dissociation mechanism leading to the desorption of O- ions. Specifically, the res ults support a channel for low-energy O- desorption, attributed to the dissociative attachment of photoelectrons, again generated in the gra phite substrate, to the physisorbed O2 molecules.