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Visualizing overdamped wavepacket motion: Excited-state isomerization of pseudocyanine in viscous solvents

Dietzek, Benjamin LU ; Tarnovsky, Alexander LU and Yartsev, Arkady LU (2009) In Chemical Physics 357(1-3). p.54-62
Abstract
The isomerization of 1,1'-diethyl-2,2'-cyanine iodide in n-alcohols is studied by femtosecond pump-probe spectroscopy. Using a broad range of probe wavelengths, the dynamics of ground-state bleach recovery, excited-state absorption and stimulation emission are monitored. We attributed the observed spectral evolution to the excited-state torsional motion, which occurs in a barrierless fashion in all solvents investigated. Excitation initiates a fast downhill bond-twisting motion on steep part of the S, potential. The rate-limiting step of the isomerization is the stochastic bond twisting on a relatively flat part of the potential at the bottom of S-1. The dependences of the bond-twisting rates on solvent viscosity are different for the... (More)
The isomerization of 1,1'-diethyl-2,2'-cyanine iodide in n-alcohols is studied by femtosecond pump-probe spectroscopy. Using a broad range of probe wavelengths, the dynamics of ground-state bleach recovery, excited-state absorption and stimulation emission are monitored. We attributed the observed spectral evolution to the excited-state torsional motion, which occurs in a barrierless fashion in all solvents investigated. Excitation initiates a fast downhill bond-twisting motion on steep part of the S, potential. The rate-limiting step of the isomerization is the stochastic bond twisting on a relatively flat part of the potential at the bottom of S-1. The dependences of the bond-twisting rates on solvent viscosity are different for the steep and flat parts of the S, potential. To the best of out knowledge, this work constitutes the first experimental observation of a process for which the viscosity dependence of the reaction rate changes along the reaction coordinate. (C) 2008 Elsevier B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Viscosity dependence, Femtosecond, Barrierless isomerization, spectroscopy
in
Chemical Physics
volume
357
issue
1-3
pages
54 - 62
publisher
Elsevier
external identifiers
  • wos:000263851800008
  • scopus:59649094525
ISSN
0301-0104
DOI
10.1016/j.chemphys.2008.10.017
language
English
LU publication?
yes
id
a724d98b-916d-46ff-a1b3-eed334ed296d (old id 1370722)
date added to LUP
2009-05-08 17:30:50
date last changed
2017-11-19 03:40:54
@article{a724d98b-916d-46ff-a1b3-eed334ed296d,
  abstract     = {The isomerization of 1,1'-diethyl-2,2'-cyanine iodide in n-alcohols is studied by femtosecond pump-probe spectroscopy. Using a broad range of probe wavelengths, the dynamics of ground-state bleach recovery, excited-state absorption and stimulation emission are monitored. We attributed the observed spectral evolution to the excited-state torsional motion, which occurs in a barrierless fashion in all solvents investigated. Excitation initiates a fast downhill bond-twisting motion on steep part of the S, potential. The rate-limiting step of the isomerization is the stochastic bond twisting on a relatively flat part of the potential at the bottom of S-1. The dependences of the bond-twisting rates on solvent viscosity are different for the steep and flat parts of the S, potential. To the best of out knowledge, this work constitutes the first experimental observation of a process for which the viscosity dependence of the reaction rate changes along the reaction coordinate. (C) 2008 Elsevier B.V. All rights reserved.},
  author       = {Dietzek, Benjamin and Tarnovsky, Alexander and Yartsev, Arkady},
  issn         = {0301-0104},
  keyword      = {Viscosity dependence,Femtosecond,Barrierless isomerization,spectroscopy},
  language     = {eng},
  number       = {1-3},
  pages        = {54--62},
  publisher    = {Elsevier},
  series       = {Chemical Physics},
  title        = {Visualizing overdamped wavepacket motion: Excited-state isomerization of pseudocyanine in viscous solvents},
  url          = {http://dx.doi.org/10.1016/j.chemphys.2008.10.017},
  volume       = {357},
  year         = {2009},
}