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Flynn, C.P. Moore, Robert David 2011-06-29T14:11:00Z 2011-06-29T14:11:00Z 10000-01-01 1979 This thesis describes an investigation of molecular photodesorption from metal and semiconductor surfaces. In the process of photodesorptiona a photon causes a molecule to desorb from the surface. The techniques employed to obtain adequate sensitivity made use of a chopped light beam and synchronous particle counting by means of a mass spectrometer. This work provides definitive measurements of the photodesorption efficiencies of several molecular species (C02, CO, H2, and CH4) from a number of metals and semiconductors. Photodesorption is a weak, temperature independent process, and it is rather difficult to measure. The photodesorbed fluxes of residual gases appear to follow Langmuir isotherms in their dependence on ambient vacuum conditions. In the one case of rare gases on aluminum, for which measurements were made on a freshly doped clean surface, no photodesorption could be observed. The variations of the observed efficiencies for photon energies between 4 and 11.5 ev point to a dominant role of intramolecular excitations in the main channel for photodesorption of more complex molecules. Previously proposed models involving band gap excitations in semiconductors and adsorbate-substrate bond excitations appear to bear no relationship to the observed effects. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-29T14:11:00Z No. of bitstreams: 1 1979_moore.pdf: 4502627 bytes, checksum: bba93b71fbecafe1bc746a29ce4ee0ba (MD5) Made available in DSpace on 2011-06-29T14:11:00Z (GMT). No. of bitstreams: 1 1979_moore.pdf: 4502627 bytes, checksum: bba93b71fbecafe1bc746a29ce4ee0ba (MD5) Previous issue date: 1979 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-29T14:11:00Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:09:33-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 397319 http://hdl.handle.net/2142/25559 en 1979 Robert David Moore photodesorption gases metal surfaces semiconductor surfaces Photodesorption of gases from metal and semiconductor surfaces Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.