| ELECTRONIC ENERGY TRANSFER BETWEEN TRIVALENT LANTHANIDE IONS IN CUBIC HEXACHLOROELPASOLITE ${CRYSTALS}^{\ast}$ (1982) | |||||||||
Abstract | |||||||||
| $^{\ast}$This work was supported by the National Science Foundation (NSF Grant CHE80-04209).. Trivalent lanthanide ions $(Ln^{3+})$ occupy sites of exact octahedral $(O_{h})$ symmetry in the cubic hexachloroelpasolite systems. Their excitation, luminescence, and energy transfer properties are, therefore, subject to highly restrictive selection rules which forbid pure $4F\rightarrow 4F$ electric-dipole electronic transition processes. This leads to relatively sparse absorption and emission spectra (comprised of magnetic dipole origins and one-quantum electric-dipole vihronic lines), and to relatively long emission lifetimes. These latter properties of the lanthanide hexachloroelpasolites make them especially attractive model systems for investigating the details of $Ln^{3+}\leftrightarrow Ln^{3+}$ electronic energy transfer processes. We report here both experimental results and theoretical analyses of energy transfer processes in a variety of systems the general formula: $Cs^{2}{NaLn_{m}}^{(d)}{Ln_{13}}^{(a)}Y_{P}Cl_{6}$, where m, n, and p are fractional stoichiometric numbers (with m + n + p = 1), $Ln^{(d)}$ demotes an energy donor ion, and $Ln^{(a)}$ denotes an acceptor ion. Special emphasis will be given the $Th^{3+} (donor)-Eu^{3+} (acceptor)$ energy transfer pair. | |||||||||
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