We report the ^{3}P_{0} → ^{3}H_{4} and ^{3}P_{0} → ^{3}H_{4} luminescence decay curves of Cs_{2}NaY_{1-x}Pr_{x}Cl_{6} at 20 K as a function of excitation wave number in the region of the transitions to the ^{3}P_{0} state near 20602 cm^{-1}, the ^{3}P_{1} state near 21200 cm^{-1} and the six components of the ^{1}I_{6} 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 PrCl_{6}^{3-} ions perturbed by a nearby water molecule.
The ^{4}I_{9/2} → ^{4}I_{15/2} luminescence decay curves for a series of complexes Er(pdc)_{n}(acac)_{3-n} (pdc = pyridine-2,6-dicarboxylate, acac = acetylacetonate, n = 0, 1, 2, 3) as solids and in dilute aqueous solutions have been investigated. The decays are multiexponential, possible reasons for this and for the short lifetimes observed are discussed.
The luminescence decay curves from the ^{4}F_{9/2} and ^{4}I_{9/2} states of the cubic hexachloroelpasolite crystals Cs_{2}NaEr_{x}Y_{1-x}Cl_{6} (x = 0.001÷1) have been measured over the temperature range 10-300 K. The ^{4}I_{9/2} state undergoes an electric dipole vibronic-electric dipole vibronic cross-relaxation process at 300 K, but this mechanism is inefficient below 165 K. Excitation into the ^{4}F_{9/2} state, results in emission in the green, blue and ultra violet regions. The up-conversion processes which could account for the ultraviolet emission are discussed.
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