Low-temperature methyl group dynamics of hexamethylbenzene in crystalline and glassy matrices as studied by 2H NMR

✍ Scribed by K. Börner; G. Diezemann; E. Rössler; H.M. Vieth

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 509 KB
• Volume: 181
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(91)80314-n

✦ Synopsis

H NMR spectra of hexamethylbenzene (HMB) in proionated crystalline and amorphous matrices at low temperatures are presented. All spectra reveal lineshape changes which can be attributed to methyl group tunnelling. Compared to neat HMB, a drastic increase of the tunnelling frequency is found for all systems. This indicates that the hindering potential originates predominantly from intermolecular forces. We studied the temperature dependence of these spectra and the spin-lattice relaxation in order to exclude a distribution of motional correlation times describing a thermally activated process. In addition, we find a distortion of the methyl tetrahedron,