¹³C spin-lattice relaxation in rotationally disordered solids

13C spin-lattice relaxation times and 14N linewidths at selected temperatures in liquid and solid I (plastic) succinonitrile are reported. Effective rotational correlation times are derived from these and the results for solid I are discussed in terms of a model which assumes that the main contributions to the rotational disorder come from gauche↔trans isomerization and the jumping of the central C-C bond of the trans species between the 3-fold axes of the b.c.c. lattice. The general applicability of the 13C technique is emphasized and the results are compared with those of other experiments reported in the literature.