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 emission bands A and B, the broad band A observed at the high-energy side under steady-state measurement conditions consists of two broad bands A' and A'' differing in their transient properties. A' is the fastest-decaying band. Each band A' and A'' is accompanied at low temperature 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 perturbed by impurities, respectively. The broad band B observed on the low-energy side grows to the detriment of emission A' and A'' with increasing 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.