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Polarized (VV) and depolarized (VH) Raman scattering have been performed on the 922 cm−1 internal line of neopentane both in the liquid phase and a multidomain single crystal of the plastic phase between 250 and 210 K. Small but systematic differences between the VV and VH spectra of the plastic phase, which are absent in the liquid phase, show anisotropy effects unrevealed up to now in this phase. The origin of the effect is discussed.

High and low frequency Raman scattering experiments have been performed in the whole temperature range of plastic neopentane (140–257 K). High frequency spectra are well accounted for by Larsson’s isotropic two‐step stochastic model when the vibrational contribution is not neglected. The discussion shows that the results are the best for the spectral part where the isotropic aspect of the model is less important. The low frequency spectra are explained by a transient dielectric anisotropy of the molecules induced by their deformation as they overcome a high potential barrier during reorientation movements. The analysis of both spectra provide consistent results for the temperature dependence of the fraction of molecules performing large amplitude rotations.