New absorption band in the near IR assigned to a bound triplet state of thef′ in NaI

Summary

TheF → F′ optical conversion in NaI is reduced by an external magnetic field, but not completely suppressed. In order to explain such unexpected result both a spin mixing in the optical cycle of theF-centre and the existence of a bound triplet state of the F′-centre have been considered. Absorption measurements have disclosed a new band at 1.4 eV whose properties are those expected in a transition from a triplet state. Moreover, its absorption intensity is in complete agreement with that calculated from the incomplete quenching of theF → F′ conversion in a magnetic field.