Study of Nuclear Magnetic Resonance Spectra of Potassium Ions in Aqueous Solutions and Estimation of the Magnetic Moment of the 39K Nucleus

The problem of increasing the accuracy of determining the magnetic moment of the potassium K-39 nucleus, which is used in studies of the norm and pathology of living tissues by nuclear magnetic resonance methods, is considered. The paper presents experimental results for determining the resonance frequency ratio of water protons and K-39 nuclei for KCl and KNO3 solutions at concentrations of 0.5-2.0 mol/kg. NMR signals from water protons and potassium nuclei were recorded simultaneously, which minimizes random and systematic errors in determining the ratio of the resonance frequencies to units of the eighth decimal place. When extrapolating the content of potassium salts in water to zero concentrations for single ions in water, the value of the above resonance frequency ratio was 21.4300226(10). Using the known data for the magnetic moment of the proton and the data for proton shielding in water, we obtained 0.390962111(18). Shielding of potassium ions in water was previously calculated in the work of Antisera and others. When using these data on the shielding of potassium ions in water, the magnetic moment of the potassium core was obtained 0.391471(8). The comparison of the new result for mu(K-39) with the data of previous works is discussed.