Luminescence parameters calculated

Several fundamental luminescence parameters were calculated for the anion of p-aminobenzoic acid on sodium acetate (11). The triplet formation efficiency (( ), the rate constant for phosphorescence... 

Those lines have been previously ascribed to Eg luminescence of Cr " " in an intermediate crystal field site (Tolstoy and Shinfue 1960 Wojtowicz 1991). Nevertheless, several contradictions prevent us from accepting such an interpretation. Excitation spectra of two types of enussion lines are very similar to those pubhshed earlier and determined as a and b environments (Platonov et al. 1998). Crystal field parameters calculated based on their excitation and polarized absorption spectra gave Dq = 1720 cm and B = 730 cm for a and Dq= 1600 cm and B = 570 cm for b environments. As was already mentioned, it was concluded that these great differences in the crystal field parameters cannot be explained by a distribution of Cr between two or more of the four crystallographicaUy different octahedral sites in the kyanite structure. The presence of a corundum precursor in kyanite was confirmed by our experiments. Nevertheless, those lines have long decay times typical for Cr in strong crystal field. 

The determination of the electronic structure of lanthanide-doped materials and the prediction of the optical properties are not trivial tasks. The standard ligand field models lack predictive power and undergoes parametric uncertainty at low symmetry, while customary computation methods, such as DFT, cannot be used in a routine manner for ligand field on lanthanide accounts. The ligand field density functional theory (LFDFT) algorithm23-30 consists of a customized conduct of nonempirical DFT calculations, extracting reliable parameters that can be used in further numeric experiments, relevant for the prediction in luminescent materials science.31 These series of parameters, which have to be determined in order to analyze the problem of two-open-shell 4f and 5d electrons in lanthanide materials, are as follows. 

Calculation of the Slater-Condon, spin-orbit coupling and ligand field parameters. The luminescence of CsMgBr3 Eu2+ is crucially dependent on the local coordination geometry of the Eu2+ dopant. Besides, a geometry change occurs in the excited state 4f 5d1 (see Table 2), leading to shifts... 

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. 

The nature of the lowest-lying excited states of the fullerenes has been difficult to identify with much certainty. From Shpol skii-type luminescence spectra recorded at 1.5 K it has been concluded that the first-excited singlet state in C70 is of A 2 character. The origins of the lowest energy transitions in Ceo, namely Si(T]g) and S2(Gg), have been assigned on the basis of fluorescence and excitation spectra, supported by theoretical calculations. " The luminescence properties and relaxation dynamics of single crystals of Qo have been described while related measurements have been made for solid films of Ceo " Similar studies have reported the luminescence spectral properties of 50 trapped inside the cavities of NiY zeolites. An analysis of the fine structure of electron-vibrational spectra has been made for 50 and its derivatives in a solid toluene matrix. The rate of triplet energy transfer between fullerenes in toluene solution has been measured as a function of temperature and used to derive thermodynamic parameters for the transfer process. ... 

The method developped by Struck and Fonger" offers the possibility for a quantitative description of the temperature quenching of broad band and narrow line emissions. The parameters which are used in this method to calculate the non-radiative rate can be obtained from the band shapes and the peak positions of the features observed in the luminescence spectra. The influence of small variations of the... 

Table 1 Structural parameters and corresponding contributions to the dipole-dipole energy transfer rate constants kj,j for the slow rise to the [Cr(bpy)3]3+ luminescence calculated by using Eq. (6) with Rc=10.6 A for the three next-nearest shells of acceptor sites...

A review (in German) has appeared concerned with the effects of microenvironment upon the luminescence properties of molecular species,480 and one in English also on solvent effects.481 Temperature effects on solvent parameters,481 a model for the ab initio calculation of solvent effects,482 and the reorientation of hydrogen-bonded solvents around a large dipole483 have been discussed. 

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