Felker, Peter M. and Zewail, Ahmed H. (1987) Purely rotational coherence effect and time-resolved sub-Doppler spectroscopy of large molecules. I. Theoretical. Journal of Chemical Physics, 86 (5). pp. 2460-2482. ISSN 0021-9606. http://resolver.caltech.edu/CaltechAUTHORS:FELjcp87
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In this and the accompanying paper we present a theoretical treatment and experimental study, respectively, of the phenomenon termed purely rotational coherence. This phenomenon has been demonstrated to be useful as a time domain means by which to obtain high resolution spectroscopic information on excited state rotational levels of large molecules [Felker et al., J. Phys. Chem. 90, 724 (1986); Baskin et al., J. Chem. Phys. 84, 4708 (1986)]. Here, the manifestations in temporally resolved, polarization-analyzed fluorescence of coherently prepared rotational levels in samples of isolated symmetric and asymmetric top molecules are considered. These manifestations, for reasonably large molecules at rotational temperatures characteristic of jet-cooled samples, take the form of polarization-dependent transients and recurrences with temporal widths of the order of tens of picoseconds or less. The transients, which arise from the thermal averaging of many single molecule coherences, are examined with respect to their dependences on molecular parameters (rotational constants, transition dipole directions) and experimental parameters (polarization directions and temperature). A physical picture of rotational coherence as a reflection of the time-dependent orientation of molecules in the sample is developed. And, the influence of rotational coherence in experiments designed to probe intramolecular energy flow is discussed. In the accompanying paper, we present experimental results for jet-cooled t-stilbene and anthracene. For t-stilbene we determine rotational constants for vibrational levels in the S1 electronic state (from the recurrences) and we monitor the trends in rotational coherence vs vibrational coherence as the total energy in the molecule increases.
|Additional Information:||© 1987 American Institute of Physics. Received 3 November 1986; accepted 24 November 1986. It is our pleasure to acknowledge F.A. Perez and J.S. Baskin for their contributions to this work. This work is supported by a grant from the National Science Foundation (DMR 85-21191). Arthur Amos Noyes Laboratory of Chemical Physics, Contribution No. 7449.|
|Subject Keywords:||FLUORESCENCE, POLYATOMIC MOLECULES, COHERENT STATES, ROTATIONAL STATES, POLARIZATION, COOLING, JETS|
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|Deposited On:||22 Sep 2008 19:56|
|Last Modified:||29 Aug 2016 19:16|
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