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Proceedings Paper

Two-color resonant four-wave mixing: a tool for double resonance spectroscopy
Author(s): Eric A Rohlfing; Joseph D. Tobiason; J. R. Dunlop; Skip Williams
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Paper Abstract

Two-color resonant four-wave mixing (RFWM) shows great promise in a variety of double- resonance applications in molecular spectroscopy and chemical dynamics. One such application is stimulated emission pumping (SEP), which is a powerful method of characterizing ground-state potential energy surfaces in regions of chemical interest. We use time-independent, diagrammatic perturbation theory to identify the resonant terms in the third- order nonlinear susceptibility for each possible scheme by which two-color RFWM can be used for double-resonance spectroscopy. After a spherical tensor analysis we arrive at a signal expression for two-color RFWM that separates the molecular properties from purely laboratory-frame factors. In addition, the spectral response for tuning the DUMP laser in RFWM-SEP is found to be a simple Lorentzian in free-jet experiments. We demonstrate the utility of RFWM-SEP and test our theoretical predictions in experiments on jet-cooled transient molecules. In experiments on C3 we compare the two possible RFWM-SEP processes and show that one is particularly well-suited to the common situation in which the PUMP transition is strong but the DUMP transitions are weak. We obtain RFWM-SEP spectra of the formyl radical, HCO, that probe quasibound vibrational resonances lying above the low threshold for dissociation to H+CO. Varying the polarization of the input beams or PUMP rotational branch produces dramatic effects in the relative intensities of rotational lines in the RFWM-SEP spectra of HCO; these effects are well described by our theoretical analysis. Finally, RFWM-SEP spectra of HCO resonances that are homogeneously broadened by dissociation confirm the predicted lineshape and give widths that are in good agreement with those determined via unsaturated fluorescence depletion SEP.

Paper Details

Date Published: 18 September 1995
PDF: 11 pages
Proc. SPIE 2548, Laser Techniques for State-Selected and State-to-State Chemistry III, (18 September 1995); doi: 10.1117/12.220849
Show Author Affiliations
Eric A Rohlfing, Sandia National Labs. (United States)
Joseph D. Tobiason, Sandia National Labs. (United States)
J. R. Dunlop, Sandia National Labs. (United States)
Skip Williams, Los Alamos National Lab. (United States)

Published in SPIE Proceedings Vol. 2548:
Laser Techniques for State-Selected and State-to-State Chemistry III
John W. Hepburn, Editor(s)

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