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Title: Perspective: Vibrational-induced steric effects in bimolecular reactions

The concept of preferred collision geometry in a bimolecular reaction is at the heart of reaction dynamics. Exemplified by a series of crossed molecular beam studies on the reactions of a C–H stretch-excited CHD{sub 3}(v{sub 1} = 1) with F, Cl, and O({sup 3}P) atoms, two types of steric control of chemical reactivity will be highlighted. A passive control is governed in a reaction with strong anisotropic entry valley that can significantly steer the incoming trajectories. This disorientation effect is illustrated by the F and O({sup 3}P) + CHD{sub 3}(v{sub 1} = 1) reactions. In the former case, the long-range anisotropic interaction acts like an optical “negative” lens by deflecting the trajectories away from the favored transition-state geometry, and thus inhibiting the bond rupture of the stretch-excited CHD{sub 3}. On the contrary, the interaction between O({sup 3}P) and CHD{sub 3}(v{sub 1} = 1) behaves as a “positive” lens by funneling the large impact-parameter collisions into the cone of acceptance, and thereby enhances the reactivity. As for reactions with relatively weak anisotropic interactions in the entry valley, an active control can be performed by exploiting the polarization property of the infrared excitation laser to polarize the reactants in space, as demonstratedmore » in the reaction of Cl with a pre-aligned CHD{sub 3}(v{sub 1} = 1) reactant. A simpler case, the end-on versus side-on collisions, will be elucidated for demonstrating a means to disentangle the impact-parameter averaging. A few general remarks about some closely related issues, such as mode-, bond-selectivity, and Polanyi’s rules, are made.« less
Authors:
 [1]
  1. Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, P.O. Box 23-166, Taipei 10617, Taiwan (China)
Publication Date:
OSTI Identifier:
22416160
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANISOTROPY; ATOMS; CHEMICAL REACTIONS; EXCITATION; HYDROCARBONS; IMPACT PARAMETER; LASER RADIATION; MOLECULAR BEAMS; ORGANIC CHLORINE COMPOUNDS; ORGANIC FLUORINE COMPOUNDS; POLARIZATION; REACTIVITY; RUPTURES