A study of electron excitations in and single crystals

Abstract

The excitation spectra of photo- and thermo-luminescence were compared in the VUV - UV spectral region in and scheelite tungstates. Temperature dependences of emission intensities and decay times were measured for in the 80 - 300 K range and approximated by a simple phenomenological model. The energy level structure of the emission centre excited state and related kinetic processes are discussed for both tungstates.

Time-resolved luminescence from Jahn-Teller split states of self-trapped excitons inPbWO4

“…The decrease of the decay time is attributed to the thermal quenching or disintegration of STE. 23,24) The present results may be explained on the basis of the APESs depicted schematically in Fig. 8.…”

“…There are two possible explanations for such decay kinetics. The photo-excitation at 266 nm creates electrons and holes, and they are separated in space and stored in traps, as pointed out by Mürk et al 24) This suggests that the decay kinetics is "spoilt" by slow delayed recombination phenomena, resulting in the non-exponential decay due to the coexistence of prompt and delayed recombination processes. Another explanation is that the high-density excitation makes nonradiative Auger process of STEs possible, in which one STE recombines nonradiatively, and transfers its energy to another STE, which is consequently decomposed into a free electron and hole.…”

SrHfO3-based phosphors and scintillators

“…non-relaxed excited state of the center, in case of PbWO 4 see e.g. [24,25]. The relaxed excited state of the luminescence center in these materials (d-orbital of Mo 6+ or W 6+ ions) might be analogous to that in SHO [26,27].…”

Paramagnetic defects in manganese-doped lead tungstate

“…In PbWO 4 , intrinsic luminescence and scintillations have an excitonic nature, and the charge transfer band in complex oxyanions (WO 4 ) 2-leads to the emission in the blue spectral region [20]. Self trapped excitons are destroyed even at a temperature of ~150 K [21]. Therefore, at room temperature, any levels of shallow traps in the PWO lattice are involved in the capture processes and become very important.…”