Resonance Coherent Anti-Stokes Raman Spectroscopy in Condensed Phases

Abstract

Coherent anti-Stokes Raman spectroscopy (CARS) has emerged as a highly efficient technique for obtaining Raman spectra of molecular species. A major drawback to the CARS technique has been a lower limit on solute concentrations of about 0.05 M due to the background signal generated by the nonresonant third order susceptibility of the solvent. This background signal is a very slowly varying function of Raman frequency [1] (see chapter on CARS in condensed phases) and remains nearly constant in intensity for typical experiments. The solute signal at ω3 can be so small for solute concentrations of less than 0.05 M as to be ‘buried’ in the background emission. Resonance enhanced CARS has greatly increased the sensitivity of the technique in analytical and structural investigations.