ZERO-FIELD SPLITTING AND LINE-SHAPE OF THE ODMR OF SELF-TRAPPED EXCITONS IN NABR

The optically detected electron paramagnetic resonance (ODMR) spectrum of self-trapped excitons (STEs) in NaBr was measured using a microwav e frequency of 25.9 GHz and compared with that measured previously at 24.0 GHz. In lock-in detected ODMR only one structureless non-Gaussian line was observed for each frequency. From the field positions of the lines obtained in the previous and new measurements a zero-held split ting of D = 1.7 T was derived. On the basis of transient ODMR measurem ents in KBr it is shown that the shape of the ODMR line does not follo w the V-K-centre nuclear spin statistics of the STE because of the dep endence of the lifetimes on the nuclear spin states. Similar effects s eem to occur in all alkali bromides.