Dynamics of NH3 photodesorption from GaAs: role of internal motion

Xiao-Yang Zhu

doi:10.1117/12.180850

21 July 1994 Dynamics of NH₃ photodesorption from GaAs: role of internal motion

Xiao-Yang Zhu

Proceedings Volume 2125, Laser Techniques for Surface Science; (1994) https://doi.org/10.1117/12.180850
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

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.

Citation Download Citation

Xiao-Yang Zhu "Dynamics of NH₃ photodesorption from GaAs: role of internal motion", Proc. SPIE 2125, Laser Techniques for Surface Science, (21 July 1994); https://doi.org/10.1117/12.180850

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