Nuclear longitudinal relaxation times in liquid D2

Results for the nuclear longitudinal relaxation time T1 in liquid D2 are presented as a function of the mole fraction X of the molecules with rotational angular momentum J=1 at T=19.9 K. A composite signal with two relaxation times was observed: a long one (T1∼103 sec)and a short one (T1≤2.3 sec)-attributed, respectively, to the molecules with J=0 and J=1. A discussion of the T1(J=1) results is made in terms of the prediction by the theory of Deutch and Oppenheim, and uses the T1 results for liquid H2. A relaxation mechanism is proposed to account for the T1(J=0) results which uses the admixture of higher-energy states into the J=0 state due to interaction with neighboring J=1 molecules. The relaxation rate for this mechanism had been calculated by Harris for solid D2 and was adapted to the liquid. Reasonable agreement between theory and experiment is found for both T1(J=1) and T1(J=0).