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

Abstract

LiCl and LiNO 3 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 3 He, 6,7 Li + , 14 NO 3 − and 35 Cl − 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 6 Li and 7 Li were established against that of the helium-3 dipole moment: µ( 6 Li) = +0.8220457(50)µ N and µ( 7 Li) = +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 provided that all shielding corrections are properly made.

Multinuclear Magnetic Resonance Study of Sodium Salts in Water Solutions

“…where νD and In general, the concentration dependences of chemical shifts/shielding for cations or anions cannot be linear, especially at concentrations above 1 M. Our analyses were done by single-variable quadratic functions and only 3 He dependences show strict linearity. It is known that virial expansions can be used for the modelling of aqueous ionic solutions (see for example [10,11]. In principle the shielding parameter at infinite dilution, when the role of counterion can be omitted, should be modeled by quantum chemical approaches.…”

“…We can slightly improve µ( 23 Na) using the new, contemporarily used m p /m e = 1836.15267389 (17) [18] to give µ( 23 Na) = 2.21608228µ N (without shielding corrections). This original value, was improved for the shielding effect in the sodium atom σ(Na) = 640.62(500) ppm calculated by adding 60.5 (10) ppm to the shielding of Na + cation according to the simple relation: σ(atom)=σ(Na + ) + 60.5 ppm (see Section 3.2 for details). This correction factor is in accordance with the theoretical result of σ (Na, atom) = 637.1 ppm achieved in theoretical relativistic calculations and cited in Reference [19].…”

“…They are admittedly not the subject of this work; however their full image is placed in Table 3. They are as follows: Q( 2 H(D)) = 0.00286(2), Q( 35 Cl) = 0.0850 (11) and Q( 23 Na) = 0.1045 (10) (all values in barn units). Analogically to the nuclear magnetic moments these values can be established by combining nuclear quadrupole coupling constants (NQCC) with theoretical calculations of electric field gradients (EFG).…”

Explorations of Magnetic Properties of Noble Gases: The Past, Present, and Future

“…The concept of the ABMR method in the more sophisticated variations can also be used for studying short-lived radioactive nuclei (isotopes with a half-life shorter than 1 min) and metastable states (a life-time of at least a few milliseconds). It is very beneficial when the NMM of nucleus is known from ABMR and NMR methods at the same time because of the possibility of comparing both results for different chemical species and verifying shielding constants and magnetic moments together (see for example [23]).…”

“…The magnetic moment of helion in a helium atom was corrected using the shielding of 3 He by its two electrons computed by Rudziński et al [43] to be σ 0 ( 3 He) = 59.96743(5) ppm, the best known shielding constant of any nuclei in any species. Gaseous helium-3 was safely used in many gaseous mixtures and water solutions for determining other NMMs or confirmation of shielding constants, e.g., 6/7 Li, 10/11 B, 13 C, 23 Na, 31 P, 35/37 Cl, and 183 W.…”