TIME-RESOLVED-PHOTOLUMINESCENCE SPECTRA OF MNO AND MNS

We have studied the time evolution of the photoluminescence spectra of MnO and MnS at different temperatures. In MnO crystals, of the two em ission bands A and B, the broad band A observed at the high-energy sid e under steady-state measurement conditions consists of two broad band s A' and A'' differing in their transient properties. A' is the fastes t-decaying band. Each band A' and A'' is accompanied at low temperatur e by a set of narrow sidebands. The emitting levels of the A' and A'' band are thermally depopulated via a level lying about 130 cm-1 higher . The A' and A'' emissions are assigned to Mn ions unperturbed and per turbed by impurities, respectively. The broad band B observed on the l ow-energy side grows to the detriment of emission A' and A'' with incr easing temperature. It is tentatively assigned to Mn2+ perturbed by Mn ions with higher valence. The results on MnS powder show similarities with those of MnO, but they are affected by some surface effects.