Laser-induced desorption and photofragmentation of small molecules adsorbed on surfaces

Qi-Zong Qin; Zhen-man Zhang; Xinju Yang; Qi-ke Zheng

doi:10.1117/12.221494

25 September 1995 Laser-induced desorption and photofragmentation of small molecules adsorbed on surfaces

Qi-Zong Qin, Zhen-man Zhang, Xinju Yang, Qi-ke Zheng

Proceedings Volume 2547, Laser Techniques for Surface Science II; (1995) https://doi.org/10.1117/12.221494
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

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.

Citation Download Citation

Qi-Zong Qin, Zhen-man Zhang, Xinju Yang, and Qi-ke Zheng "Laser-induced desorption and photofragmentation of small molecules adsorbed on surfaces", Proc. SPIE 2547, Laser Techniques for Surface Science II, (25 September 1995); https://doi.org/10.1117/12.221494

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