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Title:ROAMING ISOMERIZATION OF PHOTOEXCITED HALOGENATED ALKANES IN THE GAS AND LIQUID PHASES
Author(s):Tarnovsky, Alexander N
Contributor(s):Vorobyev, Vasily V.; Butaeva, Evgeniia V.; Mereshchenko, Andrey S.; Hicks, Christopher M.; Budkina, Darya S.; Matveev, Sergey M.; Borin, Veniamin A.
Subject(s):Mini-symposium: Multiple Potential Energy Surfaces
Abstract:Recent experimental and computational gas-phase studies have brought to light a new type of unimolecular decomposition called a “roaming mechanism. It has only been observed in the gas phase, and whether it also occurs in solution is an intriguing question. Using ultrafast transient absorption spectroscopy, we report direct isomerization of CHBr$_{3}$, BBr$_{3}$, and PBr$_{3}$ geminal tribromides in solution within the first 100 fs after S$_{1}$-excitation. The gas-phase conditions do not affect the earliest course of similar isomerization of CHBr$_{3}$. High-level ab initio simulations on XBr$_{3}$ (X = B, P, and CH) suggest that isomerization is governed by an energetically and dynamically accessible S$_{1}$/S$_{0}$ conical intersection and can be best described as a roaming-mediated pathway. Following the initial relaxation from the Franck-Condon point, “wandering” of the central atoms and migration of Br atom starts on a planar region of the S$_{1}$ surface, and in the vicinity of the conical intersection (~40 fs) the XBr$_{2}$ and Br fragments become separated to $geq$ 3 AA. After passage through the conical intersection, the partially dissociated bromine atom slips off the XBr$_{2}$ bisector plane, and forms the Br–Br bond of the BrXBr–Br isomer (~60 fs). We give examples of similar roaming isomerization in several other di- and polyhalogenated alkanes.
Issue Date:6/20/2017
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:CONFERENCE PAPER/PRESENTATION
Type:Text
Language:English
URI:http://hdl.handle.net/2142/96992
DOI:10.15278/isms.2017.TG01
Date Available in IDEALS:2017-07-27


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