EXCITATION PROFILES FOR COHERENT ANTI-STOKES RAMAN SPECTRA IN RESONANCE AND PRERESONANCE

Author Institution: Department of Chemistry, University of Georgia; Departments of Physics and Chemistry, Mississippi State UniversityExcitation profiles have been determined for lines in the coherent anti-Stokes Raman spectra of several molecules. Among these are Norharmon, $\beta$-naphthol the $\beta$-naphtholate ion and $\beta$-carotene. The experimentally determined profiles in the preresonance region for the first three molecules have been compared to those calculated using a single line approximation for CARS. The excitation profiles of two lines of $\beta$-carotene have been observed in the rigorous resonance region. The experimental data are consistent with excitation profiles calculated using the Albrecht-Tang theory modified for CARS using displacement parameters determined by Miyazawa, at al., from the spontaneous resonance Raman $study.^{1}$ A saturation effect has been noted in the rigorous resonance region, requiring the use of low laser power to obtain spectra of dilute solutions. When these conditions were met, it was found that spectra of $\beta$-carotene could be obtained at concentrations as low as $5\times 10^{-7}$ M. Experimental considerations in the determination of excitation profiles for CARS will be discussed. $^{1}$ F. Inagaki, M. Tasumi, and T. Miyazawa, J. Mol. Spectrose. 50, 286 (1974)