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Proceedings Paper

Dynamics of NH3 photodesorption from GaAs: role of internal motion
Author(s): Xiao-Yang Zhu
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Paper Abstract

Recent measurements of the photodesorption of isotope-labeled ammonia from GaAs(100) provided the first evidence for UV photodesorption from electronically-quenched, but vibrationally- excited adsorbates. The present study characterizes the quantum state distribution of photodesorbed NH3 using resonance- enhanced multiphoton ionization spectroscopy and time-of-flight spectroscopy. The translational and rotational distributions can be approximated by Boltzmann temperatures of 300+/- 20 and 350+/- 50 K, respectively, with a relative population of 6+/- 2 % in the (nu) 2equals1 vibrational level, corresponding to a vibrational temperature of 490+/- 60 K. The observed nonthermal distribution, in conjunction with measurement on coadsorbed isotope mixtures, rules out the possibility of a resonant heating mechanism, which was proposed in earlier IR laser induced desorption studies. It suggests that UV photo-induced vibrational predesorption of NH3 from GaAs occurs on a time scale shorter than that for vibrational relaxation to substrate phonons. Possible energy transfer mechanisms responsible for desorption are discussed.

Paper Details

Date Published: 21 July 1994
PDF: 7 pages
Proc. SPIE 2125, Laser Techniques for Surface Science, (21 July 1994); doi: 10.1117/12.180850
Show Author Affiliations
Xiao-Yang Zhu, Southern Illinois Univ./Carbondale (United States)

Published in SPIE Proceedings Vol. 2125:
Laser Techniques for Surface Science
Hai-Lung Dai; Steven J. Sibener, Editor(s)

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