Vacuum ultraviolet resonance Raman studies of the excited electronic states of ethylene

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Abstract
A resonance Raman study of ethylene has been performed with the use of excitation wavelengths ranging from 200 to 141 nm. Excitation resonant with the V(ππ*) state results in Raman spectra exhibiting intensity in the C=C stretching vibration, the CH2 symmetric scissors vibration, the CH2 torsional vibration and the CH2 out-of-plane wagging vibrations. These spectra confirm that the V state is strongly twisted about the C–C bond. They also indicate that the C=CH2 groups are no longer planar in the V state. Resonance with the (π3s) and (π3p) Rydberg transitions results in spectra exhibiting much less intensity in the torsional vibration, the CH2 symmetric scissors vibration and the CH2 wagging vibrations. The spectrum obtained in resonance with the (π3d) Rydberg transitions once again exhibits activity in the CH2 symmetric scissors mode.