NMR spectra of pureC13diamond

NMR measurements on single crystals of pure ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ diamond are reported. The line shape is very sensitive to the orientation of the external magnetic field relative to the crystallographic axes, typical of dipolar line broadening. With the magnetic field oriented along the [110] direction, the line is broad and flat, whereas a more narrow, Gaussian shape is seen along [001]. For the [111] direction, a spectacular line splitting of 8.5 kHz is observed. For the sample studied, the spin-lattice relaxation time was about 15 s at room temperature and 140 s at 140 K. The spectra are interpreted by a simple model using dipolar interactions.