Dynamics of molecular reorientations in t-butyl bromide studied by incoherent quasielastic neutron scattering

Abstract

The whole-molecule motions in the three solid phases of t-butyl bromide have been studied using incoherent quasielastic neutron-scattering measurements. In all three solid phases the molecules undergo rapid reorientational motion about their C—Br axes in a three-fold potential. This was the only observable motion in the lowest-temperature phase (phase III), whilst in phase II an additional motion consisting of ca. 30–60° fluctuations of the dipolar axis was found. In phase I the observed motion was consistent with a model for isotropic rotational diffusion of the molecules. A comparison between the whole-molecule reorientations in t-butyl bromide, chloride and cyanide is made.