Luminescence of CsCl:Tl crystal under synchrotron excitation

For the first time, time-resolved emission and excitation spectra, as well as decay kinetics of luminescence of CsCl : Tl single crystals have been measured at 10 K under excitation in the 4-20 eV energy range. The results obtained confirm the earlier conclusion that the emission spectrum of the main thallium centres consists of five bands arising from the trigonal (3.88 eV) and tetragonal (3.65 eV) minima of the Tl+ triplet relaxed excited state and from the on-centre (4.56 eV), weak off-centre (∼3.0 eV), and strong off-centre (2.55 eV) configurations of an exciton localized near the Tl+ ion. The origin of the excitation bands located in the 6.0-7.8 eV energy range has been discussed. The classification of various exciton emissions in CsCl crystals with respect to the lattice relaxation performed with the use of the Kan'no method has been considered. The conclusion has been made that the on-centre self-trapped exciton emission band of CsCl should be located at (5.9±0.3) eV. (Abstract Copyright [2002], Wiley Periodicals, Inc.)