TEMPERATURE-DEPENDENCE OF AUGER-FREE LUMINESCENCE IN ALKALI AND ALKALINE-EARTH HALIDES

Auger-free luminescence (AFL) resulting from a radiative transition be tween the outermost-core bands and the valence bands in BaF2, RbF, CsF , CsCl and CsBr has been studied in a wide range of temperatures from 10 to 300 K. The AFL spectra are separated from those originating from the valence-band excitation with use of time-resolved luminescence sp ectroscopy. It is found that the decay profile of AFL in each crystal is essentially the same throughout the spectrum. The remarkable therma l broadening of the linewidth is verified for all systems. This strong ly suggests that the core hole generated on a positive ion induces con siderable displacement of the surrounding ions within its lifetime, Ba sed an the present results, the spectral shape of APL is discussed in terms of a cluster model. and a two-band model, requiring further deve lopment of the investigations in theory and experiment.