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Quenched by ice: Transient grating measurements of vibronic dynamics in bromine-doped ice
 

Summary: Quenched by ice: Transient grating measurements of vibronic dynamics
in bromine-doped ice
I. U. Goldschleger, V. Senekerimyan, M. S. Krage, H. Seferyan,
K. C. Janda, and V. A. Apkariana
Department of Chemistry, University of California, Irvine, California 92697-2025
Received 9 December 2005; accepted 10 April 2006; published online 25 May 2006
In both water and in ice, the absorption spectra of bromine are dramatically broadened and
blueshifted, and all fluorescence is quenched. Time resolved, electronically resonant transient
grating measurements are carried out to characterize the vibronic dynamics of the trapped molecule
in its electronic B 3
0u state in ice. Independent of the initial excitation energy, after the first
half-period of motion, a vibrational packet is observed to oscillate near the bottom of the potential,
near =1. The oscillations undergo a chirped decay to a terminal frequency of 169 cm-1
on a time
scale of =1240 fs, to form the stationary =0 level. The electronic population in the B state
decays in e=1500 fs. Adiabatic following to the cage-compression coordinate is a plausible origin
of the chirp. Analysis of the absorption spectrum is provided to recognize that solvent coordinates
are directly excited in the process. The observed blueshift of the absorption is modeled by
considering the Br2­OH2 complex. Two-dimensional simulations, that explicitly include the solvent
coordinate, reproduce both the time data and the absorption spectrum. The observed sharp

  

Source: Apkarian, V. Ara - Department of Chemistry, University of California, Irvine

 

Collections: Chemistry