The distribution of tunnelling frequencies for methyl group rotation in poly(vinyl acetate)

The methyl group rotational tunnelling in poly(vinyl acetate) (PVAc) has been analysed by means of neutron scattering covering a range of tunnelling frequencies from μ0.5 eV to the free rotor line at 0.65 meV. The measured spectra show an apparently quasielastic broadening that has been interpreted in terms of a distribution of tunnelling frequencies. The results obtained in present experiments support those obtained previously from the analysis of the tunnelling spectrum in a smaller width window in combination with measurements in the classical hopping regime.