Raman scattering of benzene in the ultraviolet,

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Abstract
The excitation frequency dependence of intensities of the Raman active fundamentals of benzene have been measured in the uv spectral region approaching the low lying forbidden electronic states (the 1 B 2u and 1 B 1u). In accordance with theory, these forbidden states do not cntribute to the scattering cross section of any fundamental in this preresonance region. Furthermore, all but one scattering mode (the e 1g vibration) are found to derive their intensity from state in the deep vacuum uv (120 nm or above) and not the familiar strongly allowed ππ* 1 E 1u state at 185 nm. By contrast Raman scattering of the e 1g mode (848 cm−1) appears to be derived from vibronic coupling between this 1 E 1u state and a weakly allowed nearby 1 A 2u state.