High-resolution luminescence

A schematic diagram of a high-resolution luminescence spectrometer for research purposes, recently described by Vo Dinh et al. >, is shown in Fig. 24. 

Vo Dinh, T., Wild, U. P. High resolution luminescence spectrometer. 1 Simultaneous recording of total luminescence and phosphorescence. Appl. Opt. 12, 1286 (1973). 

The structural studies by X-ray diffraction and NMR have been complemented by a high-resolution luminescence analysis of the Eu "-containing complexes similar to the one conducted for the homometallic bioprobes (Section 6.3.1). Data are collected in Table 24. Firstly, the energy of the Dq —> transition calculated with Eq. (19) (see Section 3.5) and the... 

High resolution luminescence LIS Ln induced shift analysis... 

Figure 9 High-resolution luminescence spectrum of a stoichiometric 3 solution (Eu H2L ) in water/glycerol (9/1, v/v) at lOKimder ligand excitation (355 nm) [H2L ]t= 3 x 10 M. (Reproduced from Ref 17. New York Academy of Sciences, 2008)...

The octahydrate series divided structurally into two parts (La Ce and Pr Lu, Y) provides an opportunity for comparative thermoanalytical studies in which the effects of crystal structure and central ion size are studied. The octahydrates have been widely investigated by thermoanalytical techniques. The early comprehensive studies by Wendlandt and coworkers using TG and DTA techniques (Wendlandt, 1958 Wendlandt and George, 1961 Nathans and Wendlandt, 1962) have been more recently complemented by the simultaneous TG/ DTA study of Bukovec et al. (1975). These latter authors have also used DSC to determine the dehydration enthalpies. Individual rare earth sulfate hydrates have also frequently been investigated. For example, a recent study employed high-resolution luminescence spectroscopy to monitor the decomposition products of Eu2(S04)3 -SHjO during TG experiments (Brittain, 1983). 

Deng, L., et al. (2002a). High resolution (1.17 A) structure of obelin with coelenterazine h. Luminescence 17 87. 

Peaks are analyzed separately by their retention times, absorption, and fluorescence properties. RCCs show absorbance maxima near A.500 and 316 nm. For FCCs, UV-Vis specna show two prominent bands near 361 and 320 mn and a luminescence maximum at 436 mn and NCCs show UV-Vis spectra with absorbance maxima near 320 and 210 nm. Nevertheless, as none of these approaches is suitable for elucidating structures, it is necessary to apply additional MS and NMR analyses to fully characterize snuctural features. Electron spray ionization (ESI) and high-resolution EAB mass spectroscopy have been applied to elucidate the molecular formulae of colorless compounds. ... 

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... 

Shopov YY, Ford DC, Schwarcz HP (1994) Luminescent micro-banding in speleothems high-resolution chronology and paleoclimate. Geology 22 407-410... 

Special CCD cameras are used to acquire high-resolution images for scientific work. They are also called HCCD cameras. They belong to the two following classes cooled CCD cameras or intensified CCD cameras. Intensified cameras have been mostly used to follow spectroscopic fast events but they are now used in imaging to offer very high sensitivity. Cooled CCD cameras, however, offer better spatial resolution for luminescence work in the field of analysis and a broader combination of spectral ranges and sensitivity. 

Luminescence of Pr + in zircon is very difficult to detect under UV excitation even by time-resolved spectroscopy. The reason is that it has a relatively short decay time similar to those of radiation-induced centers. Visible excitation, which is not effective for broadband luminescence, allows the revealing of Pr + luminescence lines, using high-resolution steady-state spectroscopy. Under such experimental conditions each element has individual lines, enabling confident identification of the spectrum to be possible (Gaft et al. 2000a). Only if radiation-induced luminescence in zircon is relatively weak, the lines of Pr may be detected by UV excitation (Fig. 4.38c). 

Deep state experiments measure carrier capture or emission rates, processes that are not sensitive to the microscopic structure (such as chemical composition, symmetry, or spin) of the defect. Therefore, the various techniques for analysis of deep states can at best only show a correlation with a particular impurity when used in conjunction with doping experiments. A definitive, unambiguous assignment is impossible without the aid of other experiments, such as high-resolution absorption or luminescence spectroscopy, or electron paramagnetic resonance (EPR). Unfortunately, these techniques are usually inapplicable to most deep levels. However, when absorption or luminescence lines are detectable and sharp, the symmetry of a defect can be deduced from Zeeman or stress experiments (see, for example, Ozeki et al. 1979b). In certain cases the energy of a transition is sensitive to the isotopic mass of an impurity, and use of isotopically enriched dopants can yield a positive chemical identification of a level. 

Due to the modifications of the electronic cloud induced by complexation, the quantum yield and the excitation spectrum are also modified. As the direct determination of the absolute quantum yield is very difficult to achieve, one usually finds in the literature quantum yield values determined by comparison to well-known standards, such as quinine sulfate. For example, some values can be found in Georges (1993) or in Klink et al. (2000) for some europium complexes but may be found also in many other papers on lanthanide luminescence. Studies on the correlations between the photophysical properties of a given type of europium complexes and the energy levels can be found in Latva et al. (1997), Klink et al. (2000). A correlation has been found between the excitation properties and the stoichiometry of various Eu(III) complexes (Choppin and Wang, 1997). Note that the changes in the excitation maximum induced by complexation usually amount to a few tenths of nanometers, which requires high resolution for detection. In the case of Eu(III), a correlation has been found between the frequency... 

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