For the high precision measurement of a nuclear gyromagnetic ratio by the Purcell or Bloch resonance methods, accurate knowledge of the time average magnetic field $H_{\mathrm{Av}}$ at the positions of the nuclei is necessary. The various component fields contributing to $H_{\mathrm{Av}}$ are listed. An experimental study is made of two of these fields: the magnetic shielding field in molecules and the magnetization field of paramagnetic ions added to a sample. In an earlier paper accurate computed values were given of the magnetic shielding field for free atoms and monatomic ions. The effect of these fields on the attainable precision in the measurement of nuclear moments is discussed.

• Received 13 September 1950

DOI:https://doi.org/10.1103/PhysRev.81.717