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Proceedings Paper

Stroboscopic gas electron diffraction: a tool for structural kinetic studies of laser-excited molecules
Author(s): Anatoli A. Ischenko; John D. Ewbank; Vladimir A. Lobastov; Lothar Schafer
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Paper Abstract

Recent contributions by our group to the development of the experimental and theoretical bases of time-resolved studies by pulsed-beam gas electron diffraction (GED) are described. Time-resolved, stroboscopic GED experiments of laser-excited species were made possible by the development of nonphotographic, online data recording techniques. The current Arkansas detection system is characterized by an intervening light-stage that is fiber-optically coupled to either a PDA (photodiode array) or a CCD. Compared to systems in which the detector chip is directly exposed to the scattered electrons and the reactive gases inside the vacuum tank, this system is extremely durable. In experiments with a continuous electron beam, PDA detection was recently found to be one of the most precise structural tools, affording limits of precision of a few hundredths of a picometer. In kinetic studies of photo-excitation processes the traditional GED data analysis methods are not applicable because they are restricted to randomly oriented molecules with small amplitude vibrational motions in thermal equilibrium. Since laser-excited systems in general exist in nonequilibrium distributions, and the interaction with polarized laser irradiation may lead to spatially anisotropic distributions, new intensity expressions were derived for stroboscopic GED which are applicable to systems with large amplitudes, to dissociative and pre-dissociative electronic states, inverted vibrational distributions, and nonrandomly oriented molecules.

Paper Details

Date Published: 1 September 1995
PDF: 13 pages
Proc. SPIE 2521, Time-Resolved Electron and X-Ray Diffraction, (1 September 1995); doi: 10.1117/12.218344
Show Author Affiliations
Anatoli A. Ischenko, Moscow Lomonosov Univ. (Russia)
John D. Ewbank, Univ. of Arkansas/Fayetteville (United States)
Vladimir A. Lobastov, Univ. of Arkansas/Fayetteville (United States)
Lothar Schafer, Univ. of Arkansas/Fayetteville (United States)

Published in SPIE Proceedings Vol. 2521:
Time-Resolved Electron and X-Ray Diffraction
Peter M. Rentzepis, Editor(s)

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