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1
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Use of Polarization Spectroscopy in Studies of Lanthanide Complexes in Solution

100%
Riehl J.
Acta Physica Polonica A
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1996
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vol. 90
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issue 1
55-62
EN
The use of linearly or circularly polarized light in the absorption or excitation beam in spectroscopic studies involving lanthanide ions, and the analysis of emitted light polarization has provided useful information concerning molecular structure, and excited state dynamics and energetics. Linear polarization studies may be used to aid in the assignment of crystal field components of electronic transitions, and circular polarization may be employed as a probe of chiral structure and structural changes. Examples of several of the different experimental techniques are presented and discussed.
2
Content available remote

Intervalley Transfer of Electrons in ZnS-Type Thin Film Electroluminescent Devices

63%
Zhao H., Wang Y., Xu Z., Xu X.
Acta Physica Polonica A
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1999
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vol. 96
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issue 3-4
475-482
EN
Based on the calculation about intervalley scattering rates in ZnS, the intervalley transfer process in ZnS-type thin film electroluminescent devices is investigated through the Monte Carlo simulation. The transient time of intervalley transfer is about 0.2-0.3 ps, it coincides with that of electron average energy. Intervalley distribution shifts to high valleys as the electric field increased. The electron kinetic energy distributions in different valleys are also gained. We propose that high valleys could store energies, which could prolong the decay of the electron average energy as the field was removed. These results could be used as the basic data on the study of electroluminescent process and the citation of valley parameters in analytic models should be carefully considered.
3
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Theoretical and Experimental Study of the Radiative Decay Process in a Modulation Doped GaAs/AlGaAs Heterointerface

63%
Lundström T., Bergman J. P., Holtz P. O., Monemar B., Campman K., Merz J. L., Gossard A. C.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
824-828
EN
We have theoretically and experimentally investigated the radiative recombination process in an n-type modulation doped GaAs/Al_{0.35}Ga_{0.65}As heterostructure. The dynamical reshaping of the potential profile across the heterojunction, and the decay of the spatially indirect radiative recombination between electrons in the two-dimensional electron gas and photo-created holes, have been numerically simulated for various values of the electric field across the heterojunction. Optical matrix elements were deduced from a self-consistent solution of the coupled Schrodinger and Poisson equations at every discrete point of time. The calculated recombination energies and integrated luminescence intensities were compared with experimental data from time-resolved photoluminescence measurements on an 800 Å wide GaAs/AlGaAs heterostructure.
4
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Analytical Band Model in Monte Carlo Simulation of Electric Transport in ZnS Thin Film Electroluminescent Devices

63%
Zhao H., Wang Y., Xu X.
Acta Physica Polonica A
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2000
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vol. 98
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issue 1-2
123-130
EN
In this paper, an analytical band model is introduced in Monte Carlo simulation of electric transport process in thin film electroluminescent devices. The band structure of ZnS calculated from the empirical pseudopotential method is fitted by using polynomials. The density of states and scattering rates are also calculated from these polynomials. Based on these results, the electric transport process in ZnS-type thin film electroluminescent devices is simulated through the Monte Carlo method. By comparison with others, this model is as fast as the nonparabolic model and as accurate as the full band model. Furthermore, the influence of the band model on the simulation results is also investigated. We show that the dispersion relation and density of states are all important in the simulation.
5
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Energy Transfer, Fluorescence and Scintillation Processes in Cerium-Doped RE^{3+} AlO_{3} Fast Scintillators

63%
Mares J., Nikl M.
Acta Physica Polonica A
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1996
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vol. 90
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issue 1
45-54
EN
Modern applications of scintillators in medical imaging of human body (Positron Emission Tomography - PET scanning, γ-cameras and other X-ray tomographies) require improved or even quite new scintillators which should be characterized by (i) fast response, (ii) high density and (iii) high light yield. At present time new scintillating crystals are investigated, mainly those having perovskite lattice structure of the formula RE^{3+} AlO_{3}:Ce where RE ^{3+} = Y^{3+}, Gd^{3+} and Lu^{3+}. Here, we will present the newest data with summarising properties of these types of scintillators including the mixed ones. Energy transfer processes between Ce^{3+} main centres and Ce^{3+} multisites are discussed together with their mechanisms including processes between Ce ^{3+} and Gd^{3+} ions. Finally, the characteristic properties of scintillating crystals based on perovskite structure are reviewed.
6
Content available remote

Light-Induced Tautomerization in Porphyrin Isomers

51%
Waluk J.
Acta Physica Polonica A
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1999
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vol. 95
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issue 1
49-62
EN
Double proton tautomerization occurring in porphyrin and its structural isomers represents a special case of a chemical transformation in which the substrate and the product are form ally the same. The methods used for the investigation of this kind of processes are based on polarized spectroscopy and high-resolution techniques, such as matrix isolation. Their combined use results in obtaining information pertinent to the mechanism of proton transfer, regarding e.g., the values of proton transfer rates, structure of the tautomeric forms or the shape of the potential energy surfaces. In addition, these procedures provide a way of obtaining spectral, photophysical and structural data that would be otherwise difficult to gain. The examples include determination of transition moment directions, assignment of electronic and vibrational states, elucidation of the character of the substitutional replacement of the rare gas matrix atoms by the chromophore, and the analysis of the nature of the symmetry lowering due to the matrix cage.
7
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Content available

Luminescence from β-Irradiated Graphene Layers

51%
Chruścińska A., Przegiętka K., Szroeder P., Oczkowski H., Rozpłoch F.
Acta Physica Polonica A
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2006
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vol. 110
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issue 1
71-80
EN
We found that β-irradiated samples of crystallite graphite and multi-walled carbon nanotubes emit light during heating above room temperature. This behaviour is rather surprising for semimetals. Due to the lack of deep enough energy gap, this optical emission cannot be associated with interband transitions, as it is usually assumed in a thermally stimulated luminescence model. We suppose that the reported accumulated luminescence is the result of thermally stimulated relaxation of some kind of defects created in graphene structures by ionising radiation and therefore we offer to name it the relaxoluminescence. We anticipate the relaxoluminescence to be a starting point for developing a new spectroscopic method for nanotechnology. It can also throw a new light on the nature of defects, which are suspected of being responsible for strange magnetic effects in carbon.
8
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Intrinsic Luminescence of the Undoped Glasses of (CaO-Ga_{2}O_{3}-GeO_{2}) System

51%
Padlyak B., Bordun O., Buchynskii P.
Acta Physica Polonica A
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1999
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vol. 95
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issue 6
921-929
EN
For the first time the intrinsic luminescence in the undoped (CaO-Ga_{2}O_{3}-GeO_{2}) glasses with different composition has been found and investigated in the 80÷300 K temperature range. The new glasses of high chemical purity and optical quality with stoichiometric composition similar to that in calcium-gallium- germanium garnet (Ca_{3}Ga_{2}Ge_{3}O_{12}), trigonal Ca-gallogermanate (Ca_{3}Ga_{2}Ge_{4}O_{14}), and Ca_{3}Ga_{2}O_{6} crystals were obtained by the high-temperature synthesis method. The luminescence and photoexcitation spectra analysis, supported by EPR spectroscopy data, yields the following results: (i) the UV-excited non-elementary broad emission band with maxima at roughly 500 nm and 420 nm in the (CaO-Ga_{2}O_{3}-GeO_{2}) glasses is due to recombination of ensemble of the transient hole O^{-} centres; (ii) the emission bands with maxima at nearly 380 and 710 nm, which were distinctly revealed in glasses with the Ca_{3}Ga_{2}Ge_{4}O_{14} and Ca_{3}Ga_{2}O_{6} compositions, are assigned to the luminescence of UV-induced electron centres of two different types. Possible models of the luminescence centres in (CaO-Ga_{2}O_{3}-GeO_{2}) glass network are discussed.
9
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Content available

Luminescence Spectra of ZnAl_2O_4:Cr^{3+} Spinel Nanopowders

51%
Luc H., Nguyen T., Nguyen V., Suchocki A., Kamińska A., Le V., Nguyen V., Luong T.
Acta Physica Polonica A
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2003
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vol. 104
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issue 6
581-587
EN
The synthetic ZnAl_2O_4 spinels doped with Cr^{3+} ions are prepared from ZnSO_4, Al_2(SO_4)_3, and Cr_2(SO_4)_3. The spinel single phase is detected from X-ray diffraction. Luminescence properties of Cr^{3+} in ZnAl_2O_4 were studied by low temperature luminescence and decay measurements. Four luminescence lines at 14570, 14520, 14460, and 14330 cm^{-1} were found to originate from structure distortion and the line at 14175 cm^{-1} - from chromium pairs. The broad emission band at about 13540 cm^{-1} is considered to arise from a new Cr^{3+} center in ZnCr_2O_4.
10
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Microstructure and Thermally Stimulated Luminescence of β -Ga₂O₃ Thin Films

51%
Bordun O., Bordun B., Medvid I., Kukharskyy I.
Acta Physica Polonica A
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2018
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vol. 133
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issue 4
910-913
EN
Thermally stimulated luminescence of X-ray irradiated β -Ga₂O₃ thin films was investigated. An analysis of the form of the elementary contours making the thermally stimulated luminescence curves shows that recombination processes at the thermally stimulated luminescence peaks with maxima at 77, 135, 178, and 235 K in thin films of β -Ga₂O₃ are described in terms of linear kinetics. The spectral composition of the thermally stimulated luminescence of the thin films was studied. Some methods are employed to determine the activation energies and frequency factors corresponding to the thermally stimulated luminescence peaks. It is established that the recombination processes occurring upon release of the trapping centers in thin films β -Ga₂O₃ are conditioned by diffusion-controlled tunneling recombination due to thermally-stimulated migration of V_{k}-centers.
11
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Luminescence of Lanthanides from Xerogels Embedded in Mesoporous Matrices

32%
Gaponenko N.
Acta Physica Polonica A
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2007
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vol. 112
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issue 5
737-749
EN
The report summarizes peculiarities of synthesis and luminescence properties of porous silicon, porous anodic alumina and artificial opals with the inclusions of sol-gel derived oxides (xerogels), doped with Er, Tb, and Eu. Origin of strong luminescence of lanthanides from xerogels in mesoporous matrices is discussed.
12
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Ion and Electron Beam Induced Luminescence οf Rare Earth Doped YAG Crystals

23%
Gawlik G., Sarnecki J., Jóźwik I., Jagielski J., Pawłowska M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
181-183
EN
The aim of this work was the evaluation of ion-beam induced luminescence for the characterization of luminescent oxide materials containing rare earth elements. The yttrium aluminium garnet epilayers doped with Nd, Pr, Ho, and Tm atoms were used. The ion-beam induced luminescence spectra were excited using 100 keV H_2^{+} ion beam and were recorded in the wavelengths ranging from 300 nm up to 1000 nm. The separate parts of the surface of the same samples were used for ion-beam induced luminescence and cathodoluminescence experiments. Cathodoluminescence spectra have been recorded in the range from 370 nm up to 850 nm at 20 keV e-beam in scanning electron microscope equipped with a grating spectrometer coupled with a photomultiplier. The observed narrow ion-beam induced luminescence lines can be ascribed to the well known radiative transitions in the rare-earth ions in the YAG crystals. The cathodoluminescence spectra reveal essentially the same emission lines as ion-beam induced luminescence. The decrease of the ion-beam induced luminescence lines intensity has been observed under the increasing ion fluences. The ion-beam induced luminescence may be used for characterization of transparent luminescent materials as an alternative method for cathodoluminescence and can be especially useful for observation of ion-beam damage formation in crystals.
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