Luminescence lifetime data

For comparison purposes, the spectrum of LaV04 (excited at 330 nm) is given in Fig. 15. The spectra for steam aged LaY crystals containing low (1.29%) V levels is shown in Fig. 16. Luminescent lifetime data are given in Tables I and II. In all cases there are two components, (Tt and a T2), present. The T2 species are very short often exceeding limits of detection. 

TABLE II. LUMINESCENCE LIFETIME DATA FOR Sn PASSIVATED SAMPLES... 

The differences in behavior of the Eu ion in the ground and excited states may also account for the disagreement in the extent of outer-sphere complexation by chloroacetates as obtained from La-NMR data (Choppin 1980), solvent extraction (Choppin 1980) and luminescence measurements (Barthelemy and Choppin 1989a). Although NMR shift data and solvent extraction studies gave estimates of 60% and 25% inner-sphere character in the EulClAc) " and Eu(a2Ac) complexes, respectively, luminescence lifetimes data provided estimates of 100% and 50% inner-sphere character for the two complexes. 

Table 3 Typical quantum yields for typical, reasonably optimised lanthanide complexes in solutirai, estimated < Ln from luminescence lifetime data, and observed (fobs repOTted in the literature...

Proton relaxation NMR using Gd(IH) support these conclusions. Spin-lattice relaxation (Ti) values are inversely related to the average number of inner sphere hydration waters of the lanthanide cation (50-52). Chang reported hydration values of 3 and 1 for Gd complexes of EDTA and DTPA, respectively. Both NMR relaxation studies and luminescence lifetime data indicate a total coordination number between 8 and 10 for the lanthanides in aminopolycarboxylate complexes. 

Only two studies of transcurium-ion fluorescence in solution have been published. Carnall etal. (1984) measured the absorption spectrum of Bk ", interpreted its energy-level structure in terms of a free-ion energy-level model, analyzed its absorption band intensities in terms of Judd-Ofelt theory, and reported luminescence lifetime data for aquated Bk in DjO. Beitz et al. (1983) carried out LIF studies on Es " in HjO and DjO solutions as well as complexed Es " in an organic phase. No luminescence studies have been reported for actinide elements heavier than Es. 

The commercialization of inexpensive robust LED and laser diode sources down to the uv region (370 nm) and cheaper fast electronics has boosted the application of luminescence lifetime-based sensors, using both the pump-and-probe and phase-sensitive techniques. The latter has found wider application in marketed optosensors since cheaper and more simple acquisition and data processing electronics are required due to the limited bandwidth of the sinusoidal tone(s) used for the luminophore excitation. Advantages of luminescence lifetime sensing also include the linearity of the Stem-Volmer plot, regardless the static or dynamic nature of the quenching mechanism (equation 10) ... 

However, for many of these species, some peculiarities strongly limit the number of published data. From the actinide list above, Np(VI) luminescence has been observed and characterized only in solid matrix (Dewey and Hopkins, 2000). Bk, Cf and Es are hardly available in large quantities and few papers have appeared on Am(III), due to its very short luminescence lifetime, so that in practice, actinide luminescence studies are more or less restricted to U(VI) and Cm(III). Similarly, the extensive lanthanide list above is restricted mostly to Eu(III), Gd(III) and Tb(III), with fewer papers devoted to the other lanthanides. Note that Eu(II), although luminescent, is not stable in solution under normal conditions which limits the number of studies. As a consequence, this chapter reflects the tendencies described above by presenting examples mostly from Eu(III), Gd(III), Tb(III) and from U(VI) and Cm(III) studies. In solution, these ions are solvated so that either the subscript aq or solv will be used, depending on the solvent of interest. 

The energy barriers associated with the tautomerism have been determined from quantum yields and luminescence lifetime measurements <84JST(l 14)329). Table 25 lists the activation energies and solvent viscosity activation energies associated with the tautomer in a variety of alcoholic solvents. The data suggest a correlation between the energy barrier associated with proton transfer and the viscosity of the solvent. 

Determine how to fit a single exponential decay to the data to determine the luminescence lifetime, r. 

Steady-state Luminescence Quenching and Emission Lifetime Data of [Cr(phen)3] 3+ in Reaction with Guanosine... 

In addition, luminescence intensity and lifetime data obtained not only from the labelled polymer but also.from emission of dispersed naphthalene, acenaphthene and 1,1-dinaphthyl-l,3-propane (DNP) are briefly discussed. These measurements have provided information not only of relevance to the relaxation behaviour of the polymer matrix but also to the photophysies which occur therein and intramolecularly within the DNP. 

Information on the orbital nature (ligand centered, LC, or metal-to-ligand charge-transfer, MLCT) of the luminescent excited state can be drawn from the data reported in Table 2 and from their trends shown in Figure 13. For the Pt(IV) complexes the emission energy is very close to (less than 1000cm-1 red-shifted from) that of the free ligand and the luminescence lifetime is... 

Spectroscopic techniques based on the optical microscope are being used with increasing success in photophysics. Microscopic fluorescence decay measurements have been made on both thin liquid films and droplets of concentrated dye solutions.Illustrative data are given for rhodamine B in 20 pm films. A luminescence lifetime microscope spectrometer based on time-correlated single photon counting with an avalanche diode detector has measured... 

The luminescence lifetime of this complex at 77°K in glassy medium has been found to be 6.92 fisec, and the luminescence quantum yield is 0.496 (24), From these values, the intrinsic lifetime for the radiative decay of these levels at 77°K is estimated to be 14.0 jj.sec. Studies of the temperature dependence of the luminscence lifetime of similar complexes between 2° ond 100 °K indicate that the emission is caused by four thermally equilibrated levels which lie within roughly 100 cm" of one another (4), The lifetime and quantum yield data reported at 77°K are therefore representative of the Boltzmann weighted average values of these quantities for a manifold of four thermally equilibrated levels. 

Another luminescence-based method is luminescence lifetime measmement in which the decay of the excited states with time is followed [38]. Liuninescence lifetime is the time required for the intensity to decrease to 1 /e of its initial value. The most common technique is time-correlated single photon coimting which uses a pulsed light somce, one monochromator for the excitation and one for the emission side, a PMT with fast response as the detector, a time-to-amplitude converter and data storage in a multichaimel analyzer. 

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