Preresonance enhancement of the coherent anti-Stokes Raman spectra of fluorescent compounds

Preresonance excitation profiles of β-naphthol and the β-naphtholate ion have been determined by coherent anit-Stokes Raman spectroscopy (CARS). The fluorescence rejection of the CARS technique allowed Raman spectra to be obtained in a region where fluorescence would obscure the spontaneous Raman signal. A method of taking the ratio of the Raman resonant CARS signal to the background signal allowed for a more convenient and reliable method of generating CARS excitation profiles. The observed excitation profiles are in excellent agreement with those predicted using a single line approximation.