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Proceedings Paper

Laser-induced desorption and photofragmentation of small molecules adsorbed on surfaces
Author(s): Qi-Zong Qin; Zhen-man Zhang; Xinju Yang; Qi-ke Zheng
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Paper Abstract

The 266 nm UV laser-induced desorption and photofragmentation of CCl4, CF3I and CH3COCOCH3 absorbed on a quartz surface at 130 K have been investigated by time-of-flight mass spectrometry using electron impact ionization. The cryogenic molecular films are continuously condensed on a transparent quartz substrate and its thickness is monitored by a quartz crystal microbalance. The mass and the translational energy distributions are measured as a function of laser fluence and surface coverage. For CCl4, the adsorbate-mediated explosive desorption with no photodissociation is evident at high surface coverage and high laser fluence. For CF3I, the photochemical desorption associated with photofragmentation are observed at monolayer coverage on a quartz surface. For CH3COCOCH3, the electronic excitation with photodissociation of the adsorbate leads to CH3CO and CH3 radicals formation. These results reveal the characteristic electronic, thermal and explosive desorption mechanisms depending on the optical, thermal and chemical properties of the adsorbate, the film thickness and the laser irradiation conditions.

Paper Details

Date Published: 25 September 1995
PDF: 11 pages
Proc. SPIE 2547, Laser Techniques for Surface Science II, (25 September 1995); doi: 10.1117/12.221494
Show Author Affiliations
Qi-Zong Qin, Fudan Univ. (China)
Zhen-man Zhang, Fudan Univ. (China)
Xinju Yang, Fudan Univ. (China)
Qi-ke Zheng, Fudan Univ. (China)

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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