MECHANISM OF BROAD-BAND LUMINESCENCES IN ZNS PHOSPHORS .I. SPECTRUM SHIFT DURING DECAY AND WITH EXCITATION INTENSITY

The measurements of spectrum shift during decay and with excitation intensity are made for the broad-band luminescences in ZnS phosphors due to Ib activator and IIIb or VIIb coactivator, in order to investigate the luminescence mechanism. The Green-Cu Blue-Ag luminescences show remarkable spectrum shifts; namely, the emission peak shifts to lower energies during decay and also with decreasing excitation intensity. It is concluded that these luminescences are due to the so-called donor-acceptor pair emission mechanism, assuming that the donor and acceptor states involved are created, respectively, by the coactivator and activator. The self-activated luminescence shows a gradual spectrum shift at liquid helium temperature, although it shows a somewhat irregular shift at liquid nitrogen temperature. It seems that one has to assume the pair emission mechanism also for this luminescence. The Blue-Cu, Red-Cu and Red-Cu.In luminescences show no spectrum shifts. It is concluded, together with the knowledge already obtained from other measurements, that the transitions for these luminescences occur between two localized levels confined within the associated centers. © 1968.