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Proceedings Paper

Photoinduced ejection of thermal and ballistic fragments from N20/Pt(111) and NH3/Pt(111)
Author(s): Denis P. Masson; Eric J. Lanzendorf; Andrew C. Kummel
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Paper Abstract

Polarized ultraviolet light from an excimer laser (193 nm) was used to photodesorb and photodissociate N2O and NH3 adsorbed on a cold Pt(111) surface. The photodesorbed species and their time-of-flight (TOF) were monitored by Resonantly Enhanced Multiphoton Ionization spectroscopy. For N2O, we have observed both the ejection of ballistic O atoms and the release of slow thermalized N2 molecules. The ballistic oxygen atoms leave the surface either in the ground state O(3P) or in the first electronically excited state O(1D). A lobular angular distribution pointing away from the surface normal was measured for the ballistic O(3P) in agreement with a binding geometry where the linear N2O is tilted N-end down on the Pt(111) surface. Evidence for the production of N2 photofragments thermalized by the surface includes both low (approximately 90 K) rotational and translational temperatures of the N2 as well as a lack of correlation between rotational and translational energy. For NH3 the irradiation of a submonolayer coverage largely favors the desorption rather than the dissociation of NH3. For multilayer coverages however, a strong dissociation channel is activated and atomic H is seen to desorb from the surface. A bimodal distribution was found for the TOF of the H photofragments. The fastest channel (0.7 eV) corresponds to the ejection of undeflected ballistic H fragments produced near the surface. For bulk NH3 photodissociated deep within the multilayer, the TOF of the H radicals shows an unexpected thermalized distribution.

Paper Details

Date Published: 25 September 1995
PDF: 12 pages
Proc. SPIE 2547, Laser Techniques for Surface Science II, (25 September 1995); doi: 10.1117/12.221477
Show Author Affiliations
Denis P. Masson, Univ. of California/San Diego (United States)
Eric J. Lanzendorf, Univ. of California/San Diego (United States)
Andrew C. Kummel, Univ. of California/San Diego (United States)

Published in SPIE Proceedings Vol. 2547:
Laser Techniques for Surface Science II
Janice M. Hicks; Wilson Ho; Hai-Lung Dai, Editor(s)

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