Excitation luminescence

Baker A, Genty D, Smart PL (1998) High-resolution records of soil humification and paleochmatic change from variations in speleothem luminescence excitation and emission wavelengths. Geology 26 903-906 Baker A, Ito E, Smart PL, McEwan R (1997) Elevated C in speleothem and imphcations for palaeo-vegetation studies. Chem Geol 136 263-270... 

The luminescent excited state of MogClii reacts rapidly with electron acceptors(24). The powerfully oxidizing MogCli is produced in these reactions. Experiments with BSEP as acceptor in... 

Surprisingly it was found that PS luminescence excited by polarized light emerges from the sample preferentially with the same sense of polarization. This memory effect has been observed despite the fact that the electron-hole pair loses energy in the order of 1 eV in elastic processes with lifetimes in the order of... 

Rehm-Weller method (21) for estimating the reduction potentials of excited molecules As our homologous series of reductants, we have used the RuL3 +/ RuL32+ couples (22,23), where RuL32+ is the luminescent excited state of Rul 7 The electron exchange rate constants for these couples are very large... 

Stokes law spect The wavelength of luminescence excited by radiation is always greater than that of the exciting radiation. stoks, 16 )... 

Table 2.2. Main luminescence excitation bands and lines in minerals ...

Fig.8.1. Schematic representation of iuminescent sorter 1-funnei 2-vibrational feeder 3-frame 4-conveyer for concentrate 5-conveyer for waste 6-luminescence excitation source 7-collecting optics 8-optical filter 9-detector 10-air valve (Moskrousov and Lileev 1979)... 

At the present time luminescent sorters are mainly used for the processing of diamonds, but also for the scheehte, fluorite and others types of ores (Mokrousov and lileev 1979 Salter and Wyatt 1991 Gorobets et al. 1997a). The sources of luminescence excitation in these sorters are X-ray tubes and UV lamps, where the first is more powerful and the second is more selective. The UV impulse lasers employment as excitation sources enables us to combine the... 

According to spectral-kinetic parameters, the optimal conditions of luminescence excitation and detection, so called selection window (SW) parameters, were calculated in the following way. At optimal for the useful component excitation, the liuninescence spectra, decay time and intensity were determined for this mineral and for the host rock. After that, on the personal computer was calculated the proportion between useful and background signals for the full spectral region for each 50 ns after laser impulse. For calculation the spectral band was simulated by the normal distribution and the decay curve by the mono-exponential function. The useful intensity was multiplied by the weight coefficient, which corresponds to the concentration at which this component must be detected. 

A principal obstacle to identification of defects is the difficulty of comparing the results from EPR, luminescence, absorption, and deep state experiments. Probably the least ambiguous is that between EPR and luminescence when, as for transition metal impurities, it is possible for optical Zeeman measurements of a sharp luminescence line to determine the ground state g factor. If the optical and EPR measurements give the same value, then the correlation is made (Watts, 1977). In some cases, when optical excitation enhances or quenches the EPR signal, there may be a similar response in the photoconductivity or luminescence excitation spectrum. 

Fig. 14. Origin region of the low temperature excitation (luminescence monitored broad band below 20 200 cm 1) and luminescence (excitation at 457.9 nm with an Ar laser) spectra of [lr(ppy)2bpy]PF5 in [Rh(ppy)2bpy] PF6. M, C and D label electronic origins (from Ref. [45])...

Time-resolved spectroscopies of various kinds have proven useful in probing the life of an excited state. As an excited state decays, perhaps through a chain of species, time-resolved spectroscopy (e.g., luminescence, excitation, resonance Raman) can provide data for these various steps. Such studies have led, for example, to the view that the first MLCT excited state in [Ru(bipyridine)3]2+, is localized in one bipyridine ring rather than delocalized over all three rings. 

Keywords Photochemistry Photophysics Rhenium Luminescence Excited-state Abbreviations... 

Experimental technique used during these investigations is usual for Raman scattering and photoluminescence spectroscopy. For luminescence excitation He-Cd, He-Ne, and Ar+ ion lasers were used. The exciting light power not exceeds 25 mW in all experiments. 

A combination of a highly sensitive transducer based on luminescence excitation in the evanescent field with fluidic systems gives detection limits of 100 femtomoles of analyte. Such systems are well suited for antigen-antibody detection and DNA analysis [29]. 

The most intriguing fact is that this process is accompanied by a manifold, from 10 to 100 times (up to 1013 cm-2), increase in the concentration of PCs ((sSi-0-)3Si-0 and (=Si-)3C radicals) in the sample. As in the RSi samples, the latter are stabilized in the near-surface silica layers, whereas oxy radicals lie at the silica surface. The oxy radicals produce a characteristic red (620 nm) luminescence excited by the light with a wavelength of 280 nm [64], so that the samples thus prepared emit red light under UV irradiation. Due to a high concentration of the centers in fine-grained silica, this luminescence can be observed even in daylight. 

Wurtzite-structure ZnO thin films grown by a variety of deposition techniques, as well as commercially available single crystal bulk samples are discussed. Furthermore, data for ZnO thin films intermixed with numerous elements are reviewed. Most of the results are obtained by SE, which is a precise and reliable tool for measurements of the DFs. The SE results are supplemented by Raman scattering and electrical Hall-effect measurement data, as well as data reported in the literature by similar or alternative techniques (reflection, transmission, and luminescence excitation spectroscopy). 

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