Maria Czaja

The use of synchronous luminescence spectroscopy in qualitative analysis of aromatic fraction of hard coal thermolysis products

The synchronous luminescence method was used in qualitative analysis of aromatic fraction of low-temperature tar from hard coal. The spectra obtained by this method are simpler than spectra obtained with the use of conventional emission luminescence method. The synchronous luminescence analysis requires the selection of respective Deltalambda parameter values. This parameter is a constant difference between position of excitation and emission monochromators during measurement. From literature, the Deltalambda parameter value of 23 nm was first used here. The characteristic emission ranges of spectra obtained indicated (by comparison with spectra of standards) degree of condensation of aromatic compounds present in investigated mixtures. It was also possible to identify some individual compounds. However, this identification could be more effective with the use of the respective value of Deltalambda parameter for each particular component of the mixture. This manner of analysis was used here, e.g. for investigating aromatic fraction containing phenanthrene (identified previously by gas chromatography method) among other compounds. The spectrum recorded at Deltalambda value characteristic for phenanthrene (53nm) presents a rather simple shape with a maximum at 346 nm attributed to phenanthrene after standard and literature data.

Luminescence spectroscopy of Cr3+ and Mn2+ in spodumene (LiAlSi2O6)

Copyright (c) 1997 Elsevier Science B.V. All rights reserved.Luminescence emission and excitation spectra of a number of natural spodumene crystals have been measured at temperatures down to 12 K. Both Cr 3+ and Mn 2+ centres were identified; Mn 2+ is shown to be mainly in Li-sites rather than Al-sites and gives rise to a broad emission centred at 600 nm. In most spodumenes Cr 3+ R-line emission with phonon sideband is observed at temperatures below 100 K. In the more Mn-rich crystals multiple R 1 lines are seen at temperatures below about 40 K, but in Cr-rich crystals only one R 1 line is observed and Cr 3+ emission is evident at room temperature.

Fundamental parameters method for determination of rare earth elements in apatites by wavelength-dispersive X-ray fluorescence spectrometry

The determination of rare earth elements (REE) in small samples of various apatites (hydroxylapatites, carbonate-hydroxyl-fluorapatites, fluor-carbonate-hydroxylapatites, fluorapatites, fluor-meta-apatites) by wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) is presented. A small amount of the analyzed material is digested in aqua regia and then the solution obtained is pipetted onto a membrane filter. Absorption effects of the matrix elements, e.g. Ca, P, and the membrane filter are determined using an emission–transmission method. Analysis is performed using a lanthanum standard sample and theoretical calculation of the radiation intensity of REE. Therefore, standard samples for each REE are not required. Overlap of the REE peaks is also corrected theoretically using the spectrometer resolution and an approximation of the peak shape by a Gaussian function.

Aromatic compounds in molecular phase of Baltic amber—synchronous luminescence analysis

Synchronous luminescence analysis was performed in order to identify aromatic compounds in solvent extracts of Baltic amber. The investigated extracts were obtained, for comparisons, as products of extraction by various techniques and solvents. Methylene chloride and ethanol were applied independently for extraction at the ambient temperature (conservative extraction), as well as at the temperature of solvent boiling (extraction in Soxhlet apparatus). Ethanol, as the solvent, was also used for extraction in an ultrasonic bath and for the decoction process. The extraction, by techniques mentioned, of the analysed amber has resulted in products generally containing the same groups of aromatics: mainly naphthalenes, phenanthrenes and anthracenes. Among phenanthrenes, in all samples the retene was also identified, being one of the characteristic links of the diagenetic chain of chemical transformations of vegetal precursors. The identification of a series of individual compounds made, using the synchronous luminescence technique, was verified by the record of conventional emission and excitation spectra. Presented identified compounds were also confirmed by the results of GC-MS analysis. The luminescence analysis was also performed comparatively for fossil resin from Galicia, Spain (Cretaceous) older than Baltic amber (Tertiary, Eocene). The obtained preliminary results of synchronous luminescence analysis suggest the possibility of diversification in this manner of fossil resins of various ages by characterisation of aromatisation degree and alkyl substitution of aromatic rings. It is since well known that aromatisation progress is an indicator of a natural process of maturation of fossil organic matter. However, a greater number of samples should be taken to further testify to the investigations.

Magnetic susceptibility and luminescence of α-ZnAl2S4 tiospinel doped with chromium

The magnetic susceptibility as well as the optical excitation and luminescence spectra of three samples of α-ZnAl2S4 tiospinel doped with Cr at various concentrations have been measured in the temperature range 77–300 K. The susceptibility has allowed us to estimate the concentration of Cr in the samples studied as lying in the range 0.01–0.06 at.%. Crystal-field theory, including spin–orbit coupling and the trigonal crystal field of the D3d site has been used to fit the optical data. The best-fit parameters of the tiospinel crystal are B20=4800, B40=32500, B43=−28500, F(2)=58800, F(4)=40500 and ξD=300 cm−1. The computational procedure used gives excellent agreement between the experimental and calculated energy levels of the Cr3+ ion in the α-ZnAl2S4 matrix.

OPTICAL PROPERTIES OF TSAVORITE CA3AL2(SIO4)3:CR3+,V3+ FROM KENYA

Previously, a relatively large splitting of the 2Eg state of Cr3+ in grossular Ca3Al2[SiO4]3 has been reported [M. Czaja and Z. Mazurak, Opt. Mater 3 (1994) 95]. The absorption and luminescence spectra of crystals containing Cr3+ and V3+in grossular Ca3Al2(SiO4)3 garnets (variety tsavorite) have been studied for the first time. From these spectra measured at room and liquid helium temperatures we determined energies of R2, R1, and 4T2g levels of Cr3+. The lifetimes and splitting of the 2Eg state have been measured by tuning the excitation energy within the inhomogeneous profile of the R1 and R2 lines of the split 2Eg → 4A2g transition. To account for the thermal quenching of the R-lines, it is necessary to recognize that the two components of the doublet may have remarkably different radiative lifetimes (7500 and 2500 μs). These lifetimes were obtained from low temperature decay and from the temperature dependence of the intensity ratio of the R2, R1 components. These separate lifetimes as well as the lifetime of the 4T2g state were then set to fit the temperature dependence of the joint effective lifetime. The optical fluorescence of a V3+ dopant is characterized by the broad band infrared fluorescence spectrum associated with short decay time < 1μs.

Vibrational structure of luminiscence spectrum of Cr3+ in MgAl2O4

The optical absorption and luminescence spectra of MgAl2O4:Cr3+ natural spinel (from Ural) have been measured at 77 K and 293 K. The luminescent emission from 4T2g, 2Eg covers wide region of 600–750 nm. The emission spectrum at 77 K shows a very rich vibrational structure which can be mainly explained through the vibrational modes of the oxygen octahedron.

The Mössbauer spectra of prasiolite and amethyst crystals from Poland

Mössbauer spectroscopy of green (prasiolite) and violet (amethyst) quartz crystals from the Sudety Mountains (Poland) has shown that neither Fe2+ nor Fe4+ ions are present in them. Only Fe3+ ions have been identified and only in interstitial positions in channels parallel or perpendicular to the c-axis. The valence of Fe3+ ions did not change as a result of irradiation or annealing. Instead, we believe that the Fe3+ ions move within channels or between them.

Crystal-field analysis of Cr3+ in grossular Ca3Al2(SiO4)3

Abstract The optical absorption and luminescence spectra of Cr 3+ in Ca 3 Al 2 (SiO 4 ) 3 natural garnet (Grossular) measured at room and LHeT were reported the first time in Mazurak [Opt. Mater., this issue]. The spectra have been used for determined energies of R 2 , R 1 , ZPL, vibrational modes and 2 E, 4 T 2 , 4 T 1 levels. We have extended our investigations, the spectra of Cr 3+ in Ca 3 Al 2 (SiO 4 ) 3 are analyzed using a C 3i crystal-field Hamiltonian. The energy levels and the crystal-field parameters B nm for Cr 3+ ion in Ca 3 Al 2 (SiO 4 ) 3 single crystal, including spin-orbit and ligand-field interactions, have been calculated. The resulting crystal-field parameters B nm represent very well the crystal-field interactions of Cr 3+ in Grossular Ca 3 Al 2 (SiO 4 ) 3 .

Luminescence and other spectroscopic properties of purple and green Cr-clinochlore

For the first time ever, the luminescence spectra of Cr3+ centers in two chlorite crystals are presented. Chromium ions occupy the strong crystal-field site M4 in the brucite sheet and the intermediate crystal-field site in the inner octahedral sheet for purple and green chlorite, respectively. We discuss the influence of an effective positive charge on the Cr3+ ion and an effective negative charge of ligands on the differences in the values of the Dq and B parameters. It is concluded that the presence of Fe2+ ions and other point defects, as well as concentration quenching, causes the very short luminescence lifetimes of chromium ions.