THE NON-RESONANT BACKGROUND IN LASER-INDUCED GRATING EXPERIMENTS
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Date
1993
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
High pressure laser-induced grating spectroscopy experiments universally show a background that is independent of the wavelength of the excitation beams. In experiments on water vapor at atmospheric total pressures, we excite a vibrational overtone transiton in water, detecting absorption by monitoring diffraction of a probe beam via a thermal phase grating, and observe the time-dependence of the signal, both on and off resonance. The diffracted signal due to absorptive heating shows recurrences at a characteristic frequency determined entirely by experimental conditions, whereas the time-dependence of the signal when the laser is tuned off-resonance exhibits recurrences at twice the frequency of those due to absorption. Analagous condensedphase experiments have shown this off-resonance signal to be due to $electrostriction.^{1}$ Quantitative calculations of the electrostriction effect reproduce the time-dependence and magnitude of the diffracted signal observed in our experiments.
Description
$^{1}$. R.J. Miller, R. Casalegno, K.A. Nelson, and M.D. Fayer, Chem. Phys. 72, 371 (1982)
Author Institution: Department of Chemistry, University of Wisconsin-Madison; Department of Chemistry, University of California-San Diego
Author Institution: Department of Chemistry, University of Wisconsin-Madison; Department of Chemistry, University of California-San Diego