Resonance CARS spectrum of perylene in the first excited singlet (S1 ) state was observed in solution at room temperature. The observed shifts of Raman frequencies from the ground (S0 ) state values were related to the results of the PPP-SCF-CI MO calculation and the normal coordinate calculation. The experiment, intended to observe the resonance CARS signal of the S0 state, was found to give the signal predominated by the lines of the S1 state. It was also concluded that the peculiar feature originating from the simultaneous role of the pump beam depleted the molecules in the S0 state, populated the S1 state, and caused the resonance effect on CARS through the intense S1 →S0 transition.

An example of “anomalous” Raman polarization is presented by measuring the polarization dispersion of a resonant depolarized line of anthracene anion near the first absorption band. The molecular origin of the asymmetric Raman tensor is discussed on the basis of a vibronic effect associated with the resonant electronic level.

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Polarization CARS of pyrene in the SI state has been observed in solution at room temperature under the resonance condition with the Sn -SI transient absorptions. The polarization behaviors of totally symmetric a g and nontotally symmetric big modes have been interpreted on the basis of an irreducible tensor formulation of the polarization CARS susceptibility which is applicable rigorously in resonance conditions, and anomalous depolarization ratio for the big mode corresponding to the case of PI> 3/4 in spontaneous Raman scattering has been deduced.

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