ABSTRACT
Knight shifts are shifts in nuclear magnetic resonance frequencies of metal nuclei, caused by unpaired electrons in metal conduction bands. These shifts were discovered by Walter D. Knight in 1949 [1]. Knight shifts are obtained from magnetic resonance experiments on functioning superconductors. The Meissner-Ochsenfeld effect [2] prevents penetration of an external magnetic eld into a bulk superconductor, so Knight shifts must be taken as surface measurements in thin lms or powders, if the material is in a superconducting state. The electrons at the surface of a superconductor are not included in the macroscopic quantum mechanical entangled state known as superconductivity. If the electrons were a part of that state, it would not be possible to determine the magnetic resonance frequencies of adjacent nuclei and obtain the Knight shift because of the zero magnetic permeability.
