Determination of potential curve parameters of excited electronic states of polyatomic molecules by resonance CARS

Resonance CARS line‐shape analysis has been applied to determine the parameters of the excited electronic state potential curves of a cyanine dye and its short‐lived photoisomers during the process of photoisomerization. For this very complicated situation other methods for the estimation of these values would fail. The origin shift parameters determined are very small and the homogeneous line width is smaller than the line width of the absorption band.