Study of the nuclear-magnetic-resonance line shape in hcp D2

A study of the nuclear-magnetic-resonance (NMR) absorption line shape in solid hcp D2 in the nondiffusive region is presented. The mole fraction C of paramolecules (i. e., those with) a rotational angular momentum J=1) ranged from 0.02 to 0.93, and the temperature was varied between 0.5 and 10 °K. Both continuous-wave (cw) and pulse (free-induction-decay) methods were used to obtain complementing information on the NMR absorption line shape. It is shown that the line shape attributed to J=1 molecules broadens rapidly with decreasing temperature. At low enough temperatures, cw experiments record only the absorption from the J=0 molecules. Second moments M2 were obtained from the analysis of both cw and pulse experiments. Over a restricted range of molé fractions and temperatures, M2 both for the signal from all the molecules and for that from the J=0 molecules alone could be obtained separately from the free induction decay. The extrapolation of M2 to the high-temperature limit where the line shape is determined by random intermolecular nuclear dipole-dipole interactions is in good agreement with theoretical predictions. A discussion is presented of the observed and theoretically expected temperature variation of M2 for both J=1 and J=0 molecules. The results support the calculations by Harris which take account of admixtures of the J=2 excited state in the J=0 ground-state wave function, caused by the interactions with J=1 molecules.