Dynamics of orientational defects in solid adamantane

By inelastic scattering of slow neutrons from solid adamantane (C10H16) it is found that in the high-temperature phase (T > 208K) the quasi-elastic distribution contains two components, a δ-function and a Lorentzian. A comparison of the latter component to model calculations suggests that it originates from dynamical orientation defects, i.e., rotational jumps of the molecules between equilibrium orientations. The relaxation time of this motion and its temperature dependence are determined and compared to n.m.r. observations. The theoretical model also predicts a distinct dependence of the scattering on the momentum transfer. With the help of this dependence the motion can be identified in detail.