Spectroscopy and anomalous emission of Ce doped elpasolite Cs<sub>2</sub>LiY Cl<sub>6</sub>
A Bessière; P Dorenbos; C W E van Eijk; L Pidol; K W Krämer; H U Güdel
Журнал:
Journal of Physics: Condensed Matter
Дата:
2004-03-17
Аннотация:
A 10 ns fast luminescence was observed at 270 nm in Cs<sub>2</sub>LiY Cl<sub>6</sub>:Ce<sup>3+</sup> in addition to the 5d<sub>t</sub>–4f Ce<sup>3+</sup> doublet emission at 370 and 405 nm. This anomalous luminescence occurs exclusively for an excitation of the 4f–5d<sub>e</sub> transitions of Ce<sup>3+</sup> around 210 nm. It is not excited under across band gap excitation which makes it an uncommon phenomenon. The emission shows a large Stokes shift of 1.2 eV that must be related to an excited state with a very strong electron–lattice interaction or possible involvement of conduction band states. The 270 nm emission undergoes thermal quenching between 140 and 250 K while the 5d<sub>t</sub>–4f Ce<sup>3+</sup> emission gains intensity. The shape of the decay time spectra of the 5d<sub>t</sub>–4f Ce<sup>3+</sup> emission reflects a temperature activated transfer from the anomalous state to the 5d<sub>t</sub> lowest Ce<sup>3+</sup> level.
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