AbstractAnomalous polarization (ρ = 3/4 ˜∞) has been observed in the resonance Raman spectra of some acetylenecumulene dehydro annulenes of aD2hrectangular configuration. Because of no orbital degeneracy, the observed anomaly may certainly be explained by the vibronic coupling of the resonant level with nearby states. From the nature of those relevant electronic levels, the anomalous lines are assigned to theB1gmodes of vibration. For a typical anomalous polarization case, the polarization dispersion and excitation profile have been investiga