The natural line width of low field nuclear magnetic resonance spectra

Abstract The authors suggest a procedure for the determination of the natural nuclear magnetic resonance line width Δ ν of liquids using an air coil system at flux densities from 25 μT to 150 μT. Even if the line broadening caused by instrumental field inhomogeneity is much higher than Δ ν , Δ ν can be found by extrapolating the measured line width’s field dependency. For pure water this procedure yielded Δ ν  = 0.125 Hz ± 0.005 Hz. This is shown to be consistent with the smallest line width found for this sample below 25 μT using a superconducting quantum interference device-based spectrometer.