Abstracts 2001

Abstract of Publication No. 392

Markus Wermuth, Andrea Schmitz and Hans U. Güdel
Cooperative processes and upconversion in Cs2NaYCl6 codoped with Os4+ and Er3+
Phys. Rev. B 63, 245118/1-10 (2001)      Full Text (PDF)      DOI-Link     

Abstract: Halide lattices singly doped with Os4+ or Er3+ are both known to show visible upconversion luminescence upon excitation around 10000cm1. In this study, we analyze the cooperative processes in Cs2NaYCl6 codoped with Os4+ and Er3+ by measuring luminescence intensities and lifetimes. The excitation energy is found to be transferred from the G5(1T2g)/G3(1Eg) states of Os4+ to 4I11/2 and 4I13/2 of Er3+. These initial steps are followed by upconversion processes leadingto Er3+ 4S3/2 upconversion emission. The upconversion efficiency upon excitation into G5(1T2g)/G3(1Eg) of Os4+ critically depends on the Er3+ concentration, and among the Cs2NaYCl6:x%Er3+, 0.1% Os4+(x = 2, 10, and 100) samples it is highest for x = 10. The overall upconversion efficiency is limited by backtransfer processes from the Er3+ 4I11/2 and 4S3/2 states to Os4+ and by the low Os4+ concentration. An upconversion-excitation mode for Er3+ at the energy of the 4I13/2 4S3/2 excited-state absorption is observed for the title compound.

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