Question of the Paramagnetism of theMCenter in Sodium Fluoride

Abstract

A strong optical absorption band is observed in NaF at 507 mμ, and identified as the $M$ band by Ivey's law and by experiments on formation kinetics and polarization of luminescence by other workers. Not only is a substantial change in the relative intensities of the $F$ and $M$ bands possible in this substance, but also the $M$ band can be made strong compared to the $F$ without the appearance of other bands. The existence of magnetic centers in NaF is studied by means of electron spin resonance. The correlation of resonance intensity with optical studies demonstrates that no paramagnetism arises from the $M$ centers. The optical $F$ band is positively correlated with a resonance line. Resonance lines belonging to an unidentified center are reported, as are lines belonging to paramagnetic impurities.