Energy Transfer to Trace Impurities in Cs2NaY1-xPrxCl6: Consequences for Interpretation of Emission Decay Curves

S.O. Vasquez Department of Basic Chemistry, Faculty of Physical and Mathematical Sciences, University of Chile, Tupper 2069, P.O. Box 2777, Santiago, Chile and C.D. Flint Laser Laboratory, Department of Chemistry, Birkbeck College, University of London, Gordon House, 29 Gordon Square, London WC1H 0PP, United Kingdom

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We report the 3P0 → 3H4 and 3P0 → 3H4 luminescence decay curves of Cs2NaY1-xPrxCl6 at 20 K as a function of excitation wave number in the region of the transitions to the 3P0 state near 20602 cm-1, the 3P1 state near 21200 cm-1 and the six components of the 1I6 state distributed over the region 21164 to about 22000 cm-1. For x = 0.001 and excitation into the absorption maxima, the decay curves are independent of excitation wave number and of the emission transition monitored, and are exactly exponential. Excitation at regions of weak absorption between the main absorption bands produces markedly different decay curves characterised by a prominent very fast relaxation at short times and a long exponential tail. The fast decay is strongly non-exponential. On increasing the temperature, this fast process becomes less prominent, and it is not detectable in the 298 K curves. For x>=0.05 the fast process is not present at any temperature. We propose that this fast process is due to emission from PrCl63- ions perturbed by a nearby water molecule.

DOI: 10.12693/APhysPolA.90.315 PACS numbers: 13.40.Hq, 31.70.Hq, 61.72.Ss, 78.55.Hx