Kernresonanzuntersuchung der Molekülrotation und Selbstdiffusion in festem Benzol: T_1ϱ-Spektroskopie/ Nuclear Magnetic Resonance Investigation of Molecular Rotation and Diffusion in Solid Benzene: T_1ϱ-Spectroscopy

Abstract

Abstract We have extended previous NMR investigations of the molecular motion in solid benzene to lower proton spin Larmor frequencies using the rotating frame (T 1ϱ ) technique. The new data show two relaxation mechanisms, namely the well-known rotation of the benzene rings around their sixfold axis and, additionally, the self-diffusion by vacancies. The rotation and diffusion was analyzed by computer optimization of the relaxation models of Haeberlen and Torrey, respectively. The parameters of rotation are essentially consistent with results derived recently from high-frequency T 1 measurements. The diffusion parameters are in agreement with preliminary low-frequency T 1 measurements, but reveal a dramatic discrepancy by nearly 4 orders of magnitude with respect to tracer experiments of Fox and Sherwood. This behaviour is discussed in terms of correlation effects similar to those observed in plastic and liquid crystals.