C-13 AND H-1-NMR RELAXATION OF CHLOROFORM DISSOLVED IN A NEMATIC LIQUID-CRYSTAL .1. CROSS-CORRELATION BETWEEN INTRAMOLECULAR AND INTERMOLECULAR DIPOLE-DIPOLE INTERACTIONS

C-13 and H-1 relaxation times of a coupled C-13-H-1 spin system dissolved in a nematic phase have been measured at 400 MHz (for H-1) by the selective and nonselective inversion recovery method. The relaxation times of doublet lines of each spin are different from each other. Especially, when a H-1 line is inverted selectively, the relaxation time of the C-13 line connected progressively to the inverted one is fairly different depending on which line of the H-1 is inverted. Master equations for longitudinal relaxation are derived under the assumption that in addition to two relaxation mechanisms of the intramolecular dipole-dipole and external random field interactions, interference effects between the two might be nonnegligible in the oriented phase. The differences in the relaxation times have been explained by this interference effect.