The outer shoulders of the simulated spectrum are much more prominent than in the experimental spectra. Figure indicates that this is because the spectra in Figure were acquired using a too short recycle delay of 1 s. While such a short delay is suitable for liquid n-alkanes , it is clearly insufficient for the higher quadrupolar couplings of the solid methylene groups . However, since the crystalline component can still be identified using the short recycle delay, and long recycle delays increase the measurement time beyond what is practical, we continued using a recycle delay of 1 s in this work. The inner horns of the low-temperature spectra originate from the methyl groups of crystalline C30d. At 30 • C, the quadrupolar coupling of the methyl C-D bonds is decreased to one third of the rigid coupling. Such a reduction is expected for the rotation of the methyl group around its symmetry axis , showing that the methyl groups rotate with correlation times much faster than µs at the chosen temperature.