Title: Intramolecular vibrational redistribution and unimolecular reaction : concepts and new results on the femtosecond dynamics and statistics in CHBrClF
Authors : Beil, Andreas
Luckhaus, David
Quack, Martin
Stohner, Jürgen
Published in : Berichte der Bunsengesellschaft für physikalische Chemie
Volume(Issue) : 101
Issue : 3
Pages : 311
Pages to: 328
Publisher / Ed. Institution : Deutsche Bunsen Gesellschaft für Physikalische Chemie
Issue Date: 1997
License (according to publishing contract) : Licence according to publishing contract
Type of review: Not specified
Language : English
Subjects : Chemical Kinetics; Energy Transfer; Multi‐photon Processes; Photochemistry; Spectroscopy, Infrared
Subject (DDC) : 540: Chemistry
Abstract: We present the conceptual background for intramolecular vibrational (rotational) redistribution (IVR) in polyatomic molecules and its analysis from high resolution spectra. We illustrate some of the basic concepts relating to the use of effective and real molecular hamiltonians for IVR with examples drawn from our previous spectroscopic investigations of the chiral molecule CHFClBr. The importance of the initial state for the dynamics is shown, demonstrating that simple intuitive concepts of survival probabilities for some arbitrary chromophore (“zero order bright”) state are insufficient for a quantitative understanding of IVR. An approximate (C3‐like) symmetry prevents relaxation towards quasi‐equilibrium in highly excited C1‐asymmetrical CHFClBr. The coherent infrared multiphoton excitation of CHFClBr at the CH‐stretching frequency leads to coherent vibrational states with a very wide energy distribution corresponding to short time oscillatory behaviour of the CH‐stretching motion with a period of 11–12 fs. On longer time scales between 50 and 500 fs substantial vibrational motion is found in the CH‐bending coordinates. For modest excitation energies both the initial vibrational angular momentum quantum number (l = 0) and a' symmetry of the wavepacket are well conserved for 1–2 ps. At higher excitations and longer times (2–4 ps) these approximate symmetries are lost. These results are briefly discussed in relation to a general classification of IVR mechanisms and in relation to reactive processes in CHFClBr.
Departement: Life Sciences und Facility Management
Publication type: Article in scientific Journal
DOI : 10.1002/bbpc.19971010303
ISSN: 0005-9021
URI: https://digitalcollection.zhaw.ch/handle/11475/4430
Appears in Collections:Publikationen Life Sciences und Facility Management

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