Lithium-7 is a key atom in power reactors for controlling pH levels of the coolant. It is also used for producing medical research radioisotope Be-7, and in thermonuclear weapons.
Li-7 has two useful nuclei: li6 and li7, both of which are quadrupolar. They differ in sensitivity, broadening, and symmetry.
li6 has a spin of one and yields sharp signals but has low sensitivity. li7 has a spin of 1.6 and is more sensitive. Moreover, li7 has a higher quadrupolar moment so its signals are broader.
This makes li7 an important cosmological probe. It is found to be intact in halo stars and li6/li7 ratios are a strong boundary condition for the spallation of rapid particles in the early Galaxy.
7Li NMR spectroscopy in crystalline li7PSe6
The influence of local electric structures and self-diffusion on the Li dynamic in crystalline argyrodite, a promising material for all-solid-state lithium-ion batteries, is investigated by temperature-variable 7Li NMR spectroscopy combined with spin-lattice relaxation (SLR) measurements performed in the rotating frame of reference. The SLR rates log10(R1r) reveal asymmetric diffusion-induced rate peaks with activation energies as high as 0.49 eV, corresponding to long-range jump diffusion.
These results suggest that Li hopping motions are present on different length scales in the argyrodite. This can be inferred from the asymmetric peaks of SLR rates, which are correlated across the angular scale of rotation. Besides, this study reveals that SLR measurements in the rotating frame of reference can be highly suited to obtain insights into short as well as long-range hopping Li dynamics in a solid.