Reorientation of benzene in its crystalline state: A model case for the analogy between nuclear magnetic resonance spin alignment and quasielastic incoherent neutron scattering

Abstract

The close analogy between 2H-NMR spin alignment and 1H quasielastic incoherent neutron scattering [J. Chem. Phys. 84, 4579 (1986)] in determining the geometry and time scale of molecular reorientation is illustrated by an experimental example. Analysis of the final states of both methods show consistently that benzene in its (poly)crystalline state reorients by rotational jumps about the molecular sixfold symmetry axis. Emphasis is put on the quasielastic structure factor of incoherent neutron scattering, which excludes random jumps among the six orientations as the reorientation mechanism, allowing only single rotational jumps.