Two different procedures for the study of the quenching of excited states by lanthanide complex ions on the surface of micelles are considered. In the first, excited Tb(pdc)_{3}^{3-} (pdc = pyridine 2,6-dicarboxylate) complex ions are held in close proximity to other Ln(pdc)_{3}^{3-} ions on the surface of cetyl trimethyl ammonium micelles. Efficient energy transfer is observed by the electric dipole-electric dipole mechanism with a mean interaction distance only slightly greater than that which exists in the crystalline complexes. In the second, the excited state of Tb(pdc)_{3}^{3-} is depopulated by energy transfer to the coexcited lowest excited triplet state of phenanthrene which is thereby excited to the second triplet state.
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.
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 equilibria between pyridine-2,6-dicarboxylate and Eu(III) in H_{2}O or D_{2}O cetyltrimethylammonium bromide micellar solutions at room temperature have been made as a function of the ligand concentration and pH by excitation spectroscopy and emission decay measurements. Formation of the tris-complex is complete at [Eu^{3+}]:[pdc^{2-}] ≥ 1:4 at neutral to slightly alkaline conditions but is incomplete under acidic conditions. The ^{5}D_{0} lifetimes corresponding to the Eu(pdc)_{3}^{3-} anion is observed to increase on association of the complex with the micellar surface due to exclusion of the solvating molecules from the second co-ordination sphere. Energy transfer in the bulk solution requires the presence of binuclear mixed Eu^{3+} and Nd(pdc)_{3}^{3-} complexes or confinement of the Ln(pdc)_{3}^{3-}/Eu^{3+} on the micelle surface. Energy transfer from the Eu(pdc)_{3}^{3-} anion is inefficient in the bulk solution.
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.
Luminescence decay curves have been measured for the Sm^{3+} ^{4}G_{5/2} → ^{6}H_{7/2} emission in the cubic crystal Cs_{2}NaSm_{x}Eu_{y}Y_{1-x-y}Cl_{6} (x = 0.005 to x = 1, y = 0 to y = 0.99) over the temperature range 10 K to 300 K using pulsed laser excitation into the ^{4}G_{5/2} state of Sm^{3+}. The luminescence from the ^{4}G_{5/2} state of Sm^{3+} is strongly quenched by both, cross relaxation to nearest-neighbour Sm^{3+} ions and energy transfer to the ^{5}D_{0} state of Eu^{3+}. We interpret these processes in terms of a recently developed discrete shell model. The dependence of energy transfer from the Sm^{3+} donor ion to Eu^{3+} acceptor ions on y is readily studied and modelled. The temperature dependence shows that the cross relaxation occurs mainly by electric dipole vibronic-electric dipole vibronic interaction while in the energy-transfer process magnetic dipole allowed electronic contributions are also involved.
Luminescence decay curves for the ^{4}G_{5/2} → ^{6}H_{7/2} emission of Sm^{3+} in the cubic hexachloroelpasolite crystals Cs_{2}NaSm_{x}Y_{1-x}Cl_{6} (x=0.005 to x=1) and Cs_{2}NaSm_{x}Eu_{y}Y_{1-x-y}Cl_{6} (x=0.01 to x=0.95, y=0.05 to y =0.99) have been measured over the temperature range 10 K to 300 K using pulsed laser excitation into the ^{4}G_{5/2} state of Sm^{3+}. The luminescence from this state is strongly quenched by cross relaxation to Sm^{3+} acceptors and energy transfer to the ^{5}D_{0} state of Eu^{3+}. The temperature dependence of cross relaxation and of energy transfer is discussed in terms of the involved mechanisms.
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