Selectively deuterated glycerol has been subjected to 'H-NMR spin-lattice relaxation and quasi-elastic neutron scattering experiments. The measurements yield relaxation rates and a non-Gaussian &-dependence of the Debye-Waller factor which are different for the two hydrogen sites. The data analysis shows that below the onset of the glass transition aprocess the hydrogens perform a local motion (= lO-"s) in addition to what is expected from harmonic phonons. The resulting mean-square displacements are highly temperature dependent but are significantly smaller than those found in van der Waals glasses. Amplitudes and activation energies of the carbon-bonded and oxygen-bonded hydrogens are different. A possible mechanism is discussed.

2H-NMR stimulated echo experiments have been performed in order to study the molecular basis of the a-process in viscous glycerol near its glass transition temperature. Decay functions following modified Jeener-Broekaert pulse sequences were compared with predictions from different models for molecular reorientation. Rotational diffusion, rotational random jumps, rotational fixed-angle jumps and combinations of diffusive and jump motions have been tested. AIl data are fitted with a log-Gaussian distribution of correlation times. Thereby, smallbut finite-angle reorientation processes turn out to dominate in the s . .. loo s regime. Pure large-angle rotational jumps can be ruled out with high significance. The mean rotational correlation time, (7,), agrees with results from other relaxation experiments which monitor the a-process of the glass transition.

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