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Vibrational Superexchange Mechanism of Intramolecular Vibrational Relaxation in (CH_3)_3CCCH Molecules

Stuchebrukhov, A. A. and Mehta, A. and Marcus, R. A. (1993) Vibrational Superexchange Mechanism of Intramolecular Vibrational Relaxation in (CH_3)_3CCCH Molecules. Journal of Physical Chemistry, 97 (48). pp. 12491-12499. ISSN 0022-3654 . https://resolver.caltech.edu/CaltechAUTHORS:20150610-133027887

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Abstract

Quantum calculations are reported for the dynamics of intramolecular vibrational energy redistribution of the acetylenic CH stretch in (CH_3)_3CCCH molecules. This paper is an extension of our previous publication (J. Chem. Phys. 1993, 98, 6044) where the line widths of the CH overtone transitions were calculated in several molecules of a general class (CX_3)_3YCCH, and it was found that the relaxation is due to a sequence of many weak off-resonance vibrational transitions between tiers of directly coupled states. The coupling of the CH stretch to a manifold of quasi-resonant states resembles the superexchange mechanism of coupling between donor and acceptor states in long-distance electron-transfer reactions. An analysis based on total population in each tier is introduced. The very rapid decrease of this population in the intermediate tiers with tier index provides evidence that the relaxation dynamics occurs via tunneling (vibrational superexchange) under a dynamic barrier in the tier space of the system. Details of the time evolution of the population under the dynamic barrier in the course of relaxation are described. “Dead end” states, their effect on the time-evolution and on spectra, their removal via inclusion of additional anharmonicities, and, thereby, their probable artificial nature in the present case are discussed.


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http://dx.doi.org/10.1021/j100150a008DOIArticle
http://pubs.acs.org/doi/abs/10.1021/j100150a008PublisherArticle
Alternate Title:Vibrational superexchange mechanism of intramolecular vibrational relaxation in 3,3-dimethylbut-1-yne molecules
Additional Information:© 1993 American Chemical Society. Received: June 24, 1993; In Final Form: August 17, 1993. A.A.S. thanks E. J. Heller, R. D. Levine, and M. Quack for helpful discussions and critical comments during the Berlin Conference where part of this work was presented. We are pleased to acknowledge the financial support of the National Science Foundation. This work is supported in part by the Caltech-JPL CRAY Supercomputing project. R.A.M. was asked to contribute to a volume in the International Journal of Quantum Chemistry dedicated to Professor I. Hjalmars-Fischer. We were not able to meet that deadline, but it is a pleasure to acknowledge her many important scientific contributions and to dedicate this article to her.
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Caltech-JPL CRAY Supercomputing ProjectUNSPECIFIED
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Caltech Arthur Amos Noyes Laboratory of Chemical Physics8815
Issue or Number:48
Record Number:CaltechAUTHORS:20150610-133027887
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150610-133027887
Official Citation:Vibrational superexchange mechanism of intramolecular vibrational relaxation in 3,3-dimethylbut-1-yne molecules A. A. Stuchebrukhov, A. Mehta, and R. A. Marcus The Journal of Physical Chemistry 1993 97 (48), 12491-12499 DOI: 10.1021/j100150a008
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58165
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Jun 2015 21:15
Last Modified:03 Oct 2019 08:33

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