Intramolecular vibrational dephasing obeys a power law at intermediate times

Intramolecular vibrational dephasing obeys a power law at intermediate times

M. Gruebele*

Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, Urbana, IL 61801

Communicated by Ahmed H. Zewail, California Institute of Technology, Pasadena, CA (received for review January 12, 1998)

Abstract

Experimental intramolecular vibrational dephasing transients for several large organic molecules are reanalyzed. Fits to the experimental data, as well as full numerical quantum calculations with a factorized potential surface for all active degrees of freedom of fluorene indicate that power law decays, not exponentials, occur at intermediate times. The results support a proposal that power law decays describe vibrational dephasing dynamics in large molecules at intermediate times because of the local nature of energy flow.

Footnotes

↵ * To whom reprint requests should be addressed. e-mail: gruebele{at}aries.scs.uiuc.edu.
ABBREVIATIONS:

IVR,

intramolecular vibrational relaxation or redistribution;

TRFD,

time-resolved fluorescence depletion;

PES,

potential energy surface