The Radiofrequency NMR Spectra of Lithium Salts in Water; Reevaluation of Nuclear Magnetic Moments for ⁶Li and ⁷Li Nuclei

The LiCl and LiNO₃ water solutions in the presence of small amounts of 3-helium have been investigated by means of multinuclear resonance spectroscopy. The resulting concentration dependences of the ³He, ^6,7Li⁺, ¹⁴NO₃^¯ and ³⁵Cl^¯ resonance radiofrequencies are reported in the infinite limit. This data along with new theoretical corrections of shielding lithium ions was analyzed by a known NMR relationship method. Consequently, the nuclear magnetic moments of ⁶Li and ⁷Li were established against that of the helium-3 dipole moment: μ(⁶Li)=+0.822046(5)μ_N and μ(⁷Li)=+3.256418(20)μ_N. The new results were shown to be very close to the previously obtained values of the (ABMR) atomic beam magnetic resonance method. This experiment proves that our helium method is well suited for establishing dipole moments from NMR measurements performed in water solutions. This technique is especially valuable when gaseous substances of the needed element are not available. All shielding constants of species present in water solutions are consistent with new nuclear magnetic moments and these taken as a reference. Both techniques – NMR and ABMR – give practically the same results providing that all shielding corrections are properly made.