Resonance CARS line shapes: Excited state parameters for flavin adenine dinucleotide

Abstract

CARS line shapes have been measured as a function of excitation frequency for two vibrational modes, 1635 and 601 cm−1 of FAD. They are satisfactorily reproduced, over the visible absorption band, using reasonable parameters in a simple scattering model. Line shape variations from positive Lorentzian through dispersive to negative Lorentzian reflect the frequency dependence of the real and imaginary part of the Raman susceptibility when the background contribution is relatively large. The frequencies at which these features are found depend on the electronic transition frequency and bandwidth, as well as on the vibrational frequency. A method is given for determining the vibrational frequency from CARS bands with non-Lorentzian lines shapes.