Coherent Anti-Stokes Raman Spectroscopy of Polycyclic Aromatic Hydrocarbons

Abstract

Coherent anti-Stokes Raman spectroscopy (CARS) was used to obtain Raman spectra of thirteen polycyclic aromatic hydrocarbons (PAHs) composed of between three and seven fused rings. The compounds were pumped in the resonance and preresonance regions to obtain the sensitivity necessary for examination at concentrations down to 1.5 × 10 ⁻⁵ M. A simple mixture of three PAHs was optically separated through the wavelength selectivity of the resonant enhancement process. Comparisons between the spectra of the mixture and the spectrum of each pure component showed essentially no differences when pumped at the same wavelength. Finally, lineshape analysis was performed on the CARS spectra to facilitate comparisons between classes of compounds and for quantitative purposes.