Fig. 4: Relaxation dispersion profile of aqueous CuSO4 solutions in ultra-low field.
From: Zero- to low-field relaxometry of chemical and biological fluids
a ULF NMR proton spectra of aqueous solutions of CuSO4 measured in a field of 0.8 μT. The water-proton peak is shown as a function of the storage time (without CuSO4 added) and as a function of CuSO4 concentration; the storage field was 10 μT. b T2 relaxation rate as a function of the CuSO4 concentration (obtained from the average of vacuumed and non-vacuumed samples) and the linear fit with the extracted value of relaxivity. c Longitudinal relaxation rate 1/T1 of the water proton in CuSO4 solutions without and d with degassing prior to the measurements as a function of the magnetic field (left panel) and CuSO4 concentration (right panel). The dashed line in the field profile corresponds to the fit of Lorentzian function \({T}_{1}^{-1}(B)={T}_{1}^{-1}(0)/(1+{(\gamma B)}^{2}{\tau }_{c}^{2})\)14, with the correlation time τc set to 18 μs, providing an adequate match to observed experimental results. The relaxivity values are extracted from the linear fit to the average relaxation rates for various concentrations of CuSO4 across different magnetic fields. Error bars indicate standard-deviation errors of the fitting parameters.
