Effect of Paramagnetic Ions in Aqueous Solution for Precision Measurement of Proton Gyromagnetic Ratio

The measurement of proton gyromagnetic ratio }'p' has been the object of an intensive experimental program for several decades [l]-[3]. The gyromagnetic ratio of the proton is defined as a resonance frequency «p divided by a magnetic field Bo [4], when a spherical water sample at 25°C is applied by a magnetic field. The ?P' for a defined pure water sample is somewhat difficult to measure because of the weak absorption due to the long relaxation time of the proton [5]. In order to reduce the relaxation time, paramagnetic ions are added to the water sample [6]. However, as the concentration of paramagnetic ions increases, the resonance point of *H shifts and differs according to the sample shapes. The purpose of present work is to investigate the effect of paramagnetic ions(Fe*, Mn*, Co*, and Cu*) on the H NMR in paramagnetic aqueous solutions [Fe(NO3)39H2O, FeCl3, MnCl2-4H2O, CoCh-2H2O, and CuCl2-2H2O]. !H NMR in aqueous solution containing paramagnetic ions was measured as a function of concentration for the fixed spherical and cylindrical sample shapes, and the spinning cylindrical sample shape. The magnetic susceptibility per unit volume of the paramagnetic solution has also been measured as a function of concentration at room temperature. The interaction between the ' H nucleus and paramagnetic ion is discussed in terms of the shift of >H resonance point measured with two sample shapes and the magnetic susceptibility of the solution. From these experimental results, we discuss the paramagnetic solution having a short relaxation time and nearly zero shift of resonance point to implement the precision measurement of proton gyromagnetic ratio in a low magnetic field.