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Cluster Photofragmentation Dynamics: Quasiclassical Trajectory Studies of Arn-H2S and Arn-SH (n=1,2)

Published

Author(s)

J R. Fair, David Nesbitt

Abstract

Quasiclassical trajectory calculations with model potential energy surfaces have been used to elucidate the formation dynamics of open-shell radical clusters by gentle-recoil photolysis of closed-shell hydride clusters. Specifically, model surfaces for Ar-H2S and Ar2-H2S have been constructed and used to explore photofragmentation dynamics at 193 and 248 nm for comparison with previous experimental results. A remarkable efficiciency (as high as 25%) for forming highly excited radical Ar-SH and Ar2-SH clusters is calculated, despite photolysis recoil energies more than 100-fold in excess of the dissociation limit. This surprisingly high survival probability is traced to two dynamical sources. First, ejection of the light H atom from Arn-H2S effectively removes all but a small fraction of the excess photolysis energy from the nascent radical cluster in the center-of-mass fram e. Second, although trajectory calculations indicate that nearly 50% of the surviving clusters contain energies up to two-fold higher than the dissociation limit, these clusters are classically bound due to novel angular momentum barriers predicted by Pollak [J. Chem. Phys. 86, 1645 (1987)] for a polyatomic system. Finally, an analysis is presented that indicates the gentle-recoil photolysis mechanism may permit efficient formation of highly internally excited, chemically reactive radical clusters of OH and SH with light species such as H2 and D2.
Citation
Journal of Chemical Physics
Volume
113
Issue
No. 24

Keywords

clusters, photofragmentation dynamics, potential energy surface, trajectory studies

Citation

Fair, J. and Nesbitt, D. (2000), Cluster Photofragmentation Dynamics: Quasiclassical Trajectory Studies of Ar<sub>n</sub>-H<sub>2</sub>S and Ar<sub>n</sub>-SH (n=1,2), Journal of Chemical Physics (Accessed April 22, 2024)
Created November 30, 2000, Updated October 12, 2021