University of Illinois Urbana-Champaign

Roaming isomerization of photoexcited halogenated alkanes in the gas and liquid phases

Tarnovsky, Alexander N.

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2624.pdf
963008.pptx
BBr3_20_4_first_120_fs.avi
Bowman_1104386S2.mov
CHBr3_4_first_90_fs.avi

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https://hdl.handle.net/2142/96992

Description

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.
Issue Date
2017-06-20
Keyword(s)
Multiple potential energy surfaces
Date of Ingest
  • 2017-07-27T20:15:28Z
  • 2018-01-29T23:02:12Z
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.
Publisher
International Symposium on Molecular Spectroscopy
Type of Resource
text
Genre of Resource
Conference Paper / Presentation
Language
eng
Permalink
http://hdl.handle.net/2142/96992
DOI
https://doi.org/10.15278/isms.2017.TG01
Copyright and License Information
Copyright 2017 Alexander N. Tarnovsky

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Abstracts & Presentations - 2017 International Symposium on Molecular Spectroscopy PRIMARY