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Europium , nonradiative

To test the above ideas, Weitz etal.(i2) performed experiments on the fluorescence decay from a thin layer of europium(III) thenoyltrifluoracetonate (ETA) deposited on a glass slide covered with Ag particles approximately 200 A in diameter. The fluorescence decay rate was found to increase by three orders of magnitude in comparison with that of ETA in solid form. In addition to the large increase in decay rate, there was also evidence for an increase in overall fluorescence quantum efficiency. It is not possible from Eq. (8.11) to say anything about the manner in which is partitioned between radiative and nonradiative processes, y should be written in terms of a radiative part yr and a nonradiative part ynr y = yr + y r. Since the radiative rate for dipole emission is given by... [Pg.367]

Axe and Weller (52) studied fluorescence and energy transfer of europium in yttrium oxide. In an experiment somewhat similar to that of Peterson and Bridenbaugh (54) on terbium, Axe and Weller were able to obtain experimental evidence for nonradiative-energy transfer between europium and other trivalent rare earth ions. Their study included both intensity and fluorescent-lifetime measurements. [Pg.269]

Freeman, Crosby, Lawson (13), Kropp, and Windsor 17, 18) had reported that hydrated europium chloride crystals and aqueous solutions of europium salts, respectively, showed considerable enhancement of ion fluorescence and lifetimes upon substitution of H2O by D2O, the latter workers have reported (37) that wet hydrocarbon solutions of the thenoyltrifluoroacetone chelate of europium showed no enhancement of quantum yield and lifetime upon replacing the H2O present by D2O. They suggested that whereas deuteration enhanced the fluorescent properties of the free ions by inhibiting nonradiative deactivation of the Do level, the quantum efficiency of Do luminescence obtained upon direct excitation of this level (JO, 11) is already so high in the fluorinated diketone chelates e.g. thenoyltrifluoroacetone) that deuteration of the environment should have little further enhancing effect. [Pg.163]

Windsor and his co-workers 10, 11) have shown, by direct excitation of the levels in a number of europium compounds, that the quantum yield of fluorescence decreases progressively as one successively excites Do, Di, and Do. While the yield on direct excitation of Do is quite dependent on the particular compound and medium (the value is 0.82 for the thenoyltrifluoroacetone chelate in acetone solution), the proportion of the energy lost between e.g. - Do and - Do within a given compound is rather insensitive to changes in the environment. These nonradiative processes from " D and Di, whose nature is not understood, would appear to be responsible for most of the ca. 40% energy loss in these materials. [Pg.166]

Apart from forming catalysts for photochemical reactions, some rare-earth ion complexes may also form efficient luminescent materials after incorporation into microporous crystals. Alvaro et al. loaded a europium complex into zeolite Y,111831 mordenite, and ZSM-5. Because of their confinement in the zeolite framework, the chance for the luminescent centers to decay nonradiationally is reduced, and as a result the lifetime is increased in comparison with that in solution. In the meantime, upon formation of the complex, the luminescence intensity of Eu3+ ion is distinctly increased. Therefore, it is possible to prepare valuable composite luminescent materials using microporous crystals as hosts and complexes as guests. [Pg.646]

Beeby A, Clarkson IM, Dickins RS, Faulkner S, Parker D, Royle L, de Sousa AS, Williams JAG, Woods M (1999) Nonradiative deactivation of the excited states of europium, terbium and ytterbium complexes by proximate energy-matched OH, NH and CH oscillators an improved luminescence method for establishing solution hydration states. J Chem Soc Perkin Trans 2 493-503... [Pg.44]

The direct electronic excitation of lanthanide ions is very inefficient because of their low absorption coefficients and the occurrence of nonradiative deactivation processes mediated by solvent molecules, particularly by water. Therefore, sensitizing ligands are applied. These sensitizers are often termed as anterma chromo-phores. By using antenna chromophores like acridone or diaiyl ketones, the excitation wavelength for europium complexes, which is usually <370 nm, can be shifted to the visible region [5-7]. [Pg.238]


See other pages where Europium , nonradiative is mentioned: [Pg.473]    [Pg.65]    [Pg.239]    [Pg.280]    [Pg.340]    [Pg.277]    [Pg.170]    [Pg.180]    [Pg.2410]    [Pg.9]    [Pg.156]    [Pg.158]    [Pg.164]    [Pg.106]    [Pg.354]    [Pg.244]    [Pg.265]    [Pg.2409]    [Pg.277]    [Pg.257]    [Pg.308]    [Pg.29]    [Pg.83]    [Pg.85]    [Pg.92]    [Pg.106]   


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Europium

Nonradiative

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