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

Journal article

We have investigated the vacuum ultra-violet photodissociation of molecular O2 physisorbed on graphite using synchrotron radiation with photon energies in the range 13-35 eV. The yield of desorbed O+ ions shows a threshold at nearly 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 dipolar dissociation drive by photoelectrons generated in the substrate. An enchancement 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 results support a channel for low-energy O- desorption, attributed to the dissociative attachment of photoelectrons, again generated in the graphite substrate, to the physisorbed O2 molecules.

Authors: Bennett, R; Bennett, S; Siller, L; Macdonald, M; Palmer, R

• Publication status: Published
• Journal: JOURNAL OF PHYSICS-CONDENSED MATTER
• Volume: 6
• Issue: 10
• Pages: 1955-1964
• Publication date: 1994-03-07
• DOI: 10.1088/0953-8984/6/10/014
• EISSN: 1361-648X
• ISSN: 0953-8984
• Language: English