Two-color resonant four-wave mixing: Analytical expressions for signal intensity

• Published in: The Journal of chemical physics 1997-02, Vol.106 (8), p.3090-3102
• Main Authors: Williams, Skip, Rohlfing, Eric A., Rahn, Larry A., Zare, Richard N.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.473052

We present analytical signal expressions for each two-color resonant four-wave mixing (TC-RFWM) scheme that can be used for double-resonance molecular spectroscopy in the limit of weak fields (no saturation). The theoretical approach employs time-independent, diagrammatic perturbation theory and a spherical tensor analysis in an extension of recent treatments of degenerate four-wave mixing [S. Williams, R. N. Zare, and L. A. Rahn, J. Chem. Phys. 101, 1072 (1994)] and TC-RFWM for the specific case of stimulated emission pumping [S. Williams et al., J. Chem. Phys. 102, 8342 (1995)]. Under the assumption that the relaxation of the population, the orientation, and the alignment are the same, simple analytic expressions are derived for commonly used experimental configurations. The TC-RFWM signal is found to be a product of a concentration term, a one-photon molecular term, a line shape function, and a laboratory-frame geometric factor. These expressions are intended to facilitate the practical analysis of TC-RFWM spectra by clarifying, for example, the dependence on beam polarizations and rotational branch combinations.