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Wyświetlanie 1-15 z 116
Tytuł:
Free Exciton Luminescence in ZnCdSe Solid Solutions, ZnSe Epitaxial Films and ZnSe$\text{}_{1-x}$S$\text{}_{x}$/ZnSe$\text{}_{1-y}$S$\text{}_{y}$ Superlattices
Autorzy:
Tenishev, L. N.
Permogorov, S. A.
Fedorov, D. L.
Yakushcheva, G. G.
Kuznetsov, P. I
Powiązania:
https://bibliotekanauki.pl/articles/1952205.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
Opis:
We studied the luminescence of bulk Zn$\text{}_{1-x}$Cd$\text{}_{x}$Se solid solutions, epitaxial ZnSe films and ZnSe$\text{}_{1-x}$S$\text{}_{x}$/ZnSe$\text{}_{1-y}$S$\text{}_{y}$ superlattices at T=2-80 K. The analysis of the bands of exciton radiative annihilation with simultaneous emission of 1 or 2 LO phonons shows that the excitons in the studied samples can be considered as free particles with thermalized distribution of kinetic energies. In ZnSe$\text{}_{1-x}$S$\text{}_{x}$/ZnSe$\text{}_{1-y}$S$\text{}_{y}$ superlattices a three-dimensional character of exciton motion was established. The periodic potential of superlattice perturbs the exciton wave vector and induces additional elastic scattering of excitons.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 959-964
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Liquid Nitrogen and Room Temperature Reflectivity Spectra of Cd$\text{}_{1-x}$Fe$\text{}_{x}$Se in the 0.5-6.0 eV Energy Range
Autorzy:
Dębowska, D.
Zimnal-Starnawska, M.
Kisiel, A.
Giriat, W.
Powiązania:
https://bibliotekanauki.pl/articles/1931834.pdf
Data publikacji:
1994-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
Opis:
The reflectivity measurements for mixed crystals Cd$\text{}_{1-x}$Fe$\text{}_{x}$Se (0.00 ≤ x ≤ 0.10) have been carried out in an energy range of 0.5-6.0 eV at 300 and 77 K. The influence of Fe$\text{}^{2+}$(3d$\text{}^{6}$) states on the changes in the energy positions of the reflectivity maxima E$\text{}_{0}$, E$\text{}_{1}$(A$\text{}_{1}$), E$\text{}_{1}$(A$\text{}_{2}$), and E$\text{}_{1}$(B) is analyzed and the obtained results are consistent with the models existing in the literature.
Źródło:
Acta Physica Polonica A; 1994, 86, 6; 1015-1020
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Excitonic Spectra of Cd$\text{}_{1-x}$Fe$\text{}_{x}$Te Crystals
Autorzy:
Permogorov, S. A.
Tenishev, L. N.
Surkova, T. P.
Powiązania:
https://bibliotekanauki.pl/articles/1921609.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
Opis:
Strong modification of the optical spectra near the band-gap edge is observed in Cd$\text{}_{1-x}$Fe$\text{}_{x}$Te crystals as compared to the spectra of a pure compound. The evolution of the luminescence spectra at the increase in Fe concentration is represented by the change of radiative recombination channels from dominantly (A$\text{}^{0}$, x) acceptor bound exciton emission in undoped CdTe to the free exciton luminescence in Cd$\text{}_{1-x}$Fe$\text{}_{x}$Te solid solutions.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 702-704
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reflectivity Study of the Zn$\text{}_{1-x}$Co$\text{}_{x}$Se Crystals
Autorzy:
Kowalski, B. J.
Gołacki, Z.
Orłowski, B. A.
Powiązania:
https://bibliotekanauki.pl/articles/1890987.pdf
Data publikacji:
1991-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
Opis:
The room temperature reflectivity spectra of the Zn$\text{}_{1-x}$Co$\text{}_{x}$Se (x = 0, 0.03, 0.05) crystals have been measured in the visible and ultraviolet range from 1.7 to 12 eV. The structure of the spectra was interpreted in terms of the electronic band structure of the binary material (ŻnSe). The experimental results were compared with the reflectivity spectra of the Fe-based semi magnetic semiconductors [1], and the interpretation was confronted with the conclusions derived from the photoemission experiments performed for Cd$\text{}_{1-x}$Co$\text{}_{x}$Se [2] and the tight-binding CPA calculations of the band structure of Zn$\text{}_{1-x}$Co$\text{}_{x}$Se [3].
Źródło:
Acta Physica Polonica A; 1991, 80, 3; 393-396
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of Some Heavyweight Aggregate Half Value Layer Thickness Used for Radiation Shielding
Autorzy:
Akkurt, İ.
Başyiğit, C.
Akkaş, A.
Kılınçarslan, Ş.
Mavi, B.
Günoğlu, K.
Powiązania:
https://bibliotekanauki.pl/articles/1490934.pdf
Data publikacji:
2012-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
Opis:
A radiation dose above the maximum permissible limit is very dangerous for human being. In radiation shielding, absorbent materials' properties must be well known. Heavyweight concrete is the most widely used in the world for this aim. The aggregate component of concrete plays an important role in improving concrete properties and this is effect of shielding properties of concrete. The thickness of any given material where 50% of the incident energy has been attenuated is known as the half-value layer. The half-value layer is expressed in units of distance (mm or cm). Like the attenuation coefficient, it is photon energy dependent. Increase of the penetrating energy of a stream of photons will result in an increase in a material's half-value layer. In this study, half-value layer thickness of concrete containing limonite, siderite and barite at different ratios was investigated; for this purpose measurements have been obtained by a collimated beam of gamma ray from sources $\text{}^{60}Co$. The total linear attenuation coefficient (μ), half-value layer thickness is evaluated in this study.
Źródło:
Acta Physica Polonica A; 2012, 121, 1; 138-140
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reflectivity Study of HgSe$\text{}_{1-x}$Te$\text{}_{x}$ Crystals
Autorzy:
Kowalski, B. J.
Dybko, K.
Lemańska, A.
Orłowski, B. A.
Powiązania:
https://bibliotekanauki.pl/articles/1923860.pdf
Data publikacji:
1992-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
Opis:
The room temperature reflectivity spectra of HgSe$\text{}_{1-x}$Te$\text{}_{x}$ (x = 0, 0.4, 0.5, 1.0) crystals were measured in the visible and ultraviolet range from 1.5 to 12 eV. The maxima characteristic of the binary HgA$\text{}^{IV}$ compounds can be revealed in the mixed crystals spectra, but their position depends on the crystal composition. There is no duplication of the spectral features in spite of the different energy position of the maxima for HgSe and HgTe. This suggests that the virtual crystal approximation could be used to describe basic optical properties of HgSe$\text{}_{1-x}$Te$\text{}_{x}$.
Źródło:
Acta Physica Polonica A; 1992, 82, 5; 845-848
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Saturation Processes in Nonlinear Media Modeled by Four-Level Configuration with Coincident Absorption and Emission Bands
Autorzy:
Addasi, J.
Powiązania:
https://bibliotekanauki.pl/articles/1419788.pdf
Data publikacji:
2012-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Bh
78.20.Ci
Opis:
The four-level model is used to study the nonlinear media with coincident absorption and emission bands in both principal $(S_0-S_1)$ and excited $(T_1-T_2)$ channels. The excitation of molecules occurred by two light fields: radiations with intensity $I_{12}$ at frequency $\omega_0$ tuned at the centre of absorption band of principal singlet-singlet channel and radiations with intensity $I_{34}$ at frequency ω tuned at the centre of absorption band of excited triplet-triplet channel. The monotonic dependence of phase response of media in both principal and excited channels and the saturation processes are studied theoretically and numerically for four-level model.
Źródło:
Acta Physica Polonica A; 2012, 122, 1; 156-158
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Linear Dichroism Spectra of Doped Calcium Gallogermanate Crystals
Autorzy:
Shopa, Y.
Ftomyn, N.
Powiązania:
https://bibliotekanauki.pl/articles/1550185.pdf
Data publikacji:
2010-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
78.20.Fm
Opis:
Polarized absorption and linear dichroism spectra of chromium and manganese doped gallogermanate $(Ca_{3}Ga_{2}Ge_{4}O_{14})$ crystals were measured and analyzed. Electronic transitions were identified and crystal field parameters have been determined. The value of linear dichroism obtained at the wavelength of 633 nm was compared with polarimetric measuring data for chromium doped $Ca_{3}Ga_{2}Ge_{4}O_{14}$ crystals.
Źródło:
Acta Physica Polonica A; 2010, 117, 1; 114-116
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dielectric Permeability of Nanocylinder
Autorzy:
Jaćimovski, S.
Sajfert, V.
Raković, D.
Tošić, B.
Powiązania:
https://bibliotekanauki.pl/articles/1537830.pdf
Data publikacji:
2010-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
78.40.Me
Opis:
In the nanocylinder, a cut-off from the molecular crystal, dielectric permeability tensor is investigated. Excitons in the nanocylinder arise due to the exciting of the electron subsystem of the molecule. In evaluation of dielectric permeability Dzhyaloshinskii-Pitaevskii approach is used, connected with retarded and advanced exciton Green's functions and correct use of Paulion Green's function. It turned out that refraction and absorption indices depend on configuration coordinates, having maximal values at boundary cross-sections and minimal value at central cross-section of the nanocylinder broken symmetry structure. Although it was expected that boundary conditions make higher refractive and absorptive characteristics of the nanocylinder, this appeared not to be possible because Paulion Green's function is not proportional to the exciton concentration.
Źródło:
Acta Physica Polonica A; 2010, 117, 5; 738-744
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Model Study of Inhomogeneous Line Broadening in Excitonic Spectra of Quantum Wells
Autorzy:
Astakhov, G. V.
Kochereshko, V. P.
Kosobukin, V. A.
Yakovlev, D. R.
Wojtowicz, T.
Karczewski, G.
Kossut, J.
Ossau, W.
Landwehr, G.
Powiązania:
https://bibliotekanauki.pl/articles/1969005.pdf
Data publikacji:
1998-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
78.66.-w
Opis:
An approach is proposed to estimate separately parameters of homogeneous and inhomogeneous broadenings from an optical reflection line of a quasi-2D exciton. A phenomenological model is proposed to take into account statistically an inhomogeneous broadening of the exciton resonant spectra. The concept is applied to study a modulation-doped heterostructures with a single quantum well CdTe/CdMgTe. From exciton reflection lines taken in a magnetic field the temperature-dependent homogeneous and inhomogeneous broadening parameters as well as the exciton radiative decay rate are measured.
Źródło:
Acta Physica Polonica A; 1998, 94, 2; 235-239
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ellipsometric Studies of NdMnO$\text{}_{3}$ Single Crystals
Autorzy:
Babonas, G. J.
Reza, A.
Szymczak, R.
Baran, M.
Shiryaev, S.
Fink-Finowicki, J.
Szymczak, H.
Powiązania:
https://bibliotekanauki.pl/articles/2037130.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
78.20.Ci
Opis:
Ellipsometric studies of NdMnO$\text{}_{3}$ single crystals of orthorhombic symmetry were carried out in the spectral range 0.5-5.0 eV. Experimental data, which were obtained on the (001)$\text{}_{pc}$-type planes of pseudo-cubic system, were analyzed in the model of biaxial crystal. For the first time, three componentsε$\text{}_{x}$,ε$\text{}_{y}$,ε$\text{}_{z}$ of the effective dielectric function for manganites of orthorhombic symmetry were determined. From ellipsometric data, the spectra of optical conductivity and loss function were also calculated and considered. The fine structure of the spectra and optical anisotropy was the basis for discussion of the microscopic origin of the optical transitions responsible for the optical features. The electronic excitations due to dipole-forbidden spin-allowed transitions of the d-d-type in Mn-ions, f-f-type in Nd-ions and charge-transfer 2p(O)-3d(Mn) transitions were taken into account. The data for NdMnO$\text{}_{3}$ were compared with those obtained for other related undoped and doped single crystals of perovskite-type structure, LaMnO$\text{}_{3}$, (LaBa)(MnCo)O$\text{}_{3}$ and (LaCa)CoO$\text{}_{3}$.
Źródło:
Acta Physica Polonica A; 2004, 105, 1-2; 197-208
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Systematic Variation of Optical Properties of Alkali Halides: an Ab Initio Study
Autorzy:
Gonçalves, G. C.
Lalic, M. V.
Malta, O. L.
Powiązania:
https://bibliotekanauki.pl/articles/2047877.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Dg
78.20.Ci
Opis:
In this paper we study a correlation between the optical properties, electronic structure and anion-cation electronegativity difference in three groups of alkali halides MX (M = Li, Na, K; X = F, Cl, Br, I). The electronic structure was calculated by first-principle, density-functional theory based full-potential linear augmented plane wave method. Then the complex dielectric function was computed, allowing determination of the optical absorption spectra in all compounds, up to incident radiation energy of 40 eV. The results were interpreted in terms of calculated band structures and correlated with the electronegativity difference in each compound, which was estimated on the basis of topological theory of Bader.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 1043-1048
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Negative Refraction as a Source of Some Pedagogical Problems
Autorzy:
Veselago, V.
Powiązania:
https://bibliotekanauki.pl/articles/1814051.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
41.20.Jb
Opis:
The appearance of material with negative values of dielectric and magnetic permeabilities ε and μ and with negative index of refraction n forces to revise the accustomed forms of some well-known formulae of electrodynamics. This is connected with fact, that these correlations in repressing majority of sources is written in tacit suggestion that magnetic permeability of most of materials is μ=1, factor of refraction n=ε and is undoubtedly executed the correlation n > 0. Such approach could be named as "nonmagnetic". However, if n <0, this nonmagnetic approach can bring very hard mistakes.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 777-781
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oscillations in Reflectivity of Samples with X-ray Waveguide Layers
Autorzy:
Pełka, J. B.
Lagomarsino, S.
Di Fonzo, S.
Jark, W.
Domagała, J.
Powiązania:
https://bibliotekanauki.pl/articles/1945221.pdf
Data publikacji:
1996-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.65.+g
78.20.Ci
Opis:
The glancing-angle reflectivity profiles in samples containing an X-ray waveguide layer are studied. Oscillations observed at angles within the region of resonance and above, are interpreted by angle dependent interference of the monochromatic X-ray beam in thin layer. The discussion is extended to the structures composed of more than one layer. Experimental reflectivity spectra recorded with Cu K$\text{}_{α}$ radiation are compared with the theoretical calculations. It leads to the model of oscillations in reflectivity consistent both for the resonant and non-resonant regions, and clarifies interpretation of oscillations in the region above the resonances. A brief discussion of potential applications of the reflectivity spectra to the studies of structure of thin layers is done.
Źródło:
Acta Physica Polonica A; 1996, 89, 3; 323-328
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Radiation Shielding Properties of Polypropylene Fiber Reinforced Shotcrete
Autorzy:
Çakıroğlu, M.
Powiązania:
https://bibliotekanauki.pl/articles/1186770.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Ni
78.20.Ci
Opis:
Fibre concrete has emerged in order to improve the properties of concrete and to create an economical building material. In this study, the radiation permeability of shotcrete reinforced with polypropylene fiber was investigated. For this purpose, linear attenuation coefficient was measured for shotcrete reinforced with polypropylene fiber, produced using the dry mixing process. The linear attenuation coefficients for dry mixed shotcrete have been measured at photon energies of 1173, 1332 and 662 keV. Measurements were carried out using gamma spectrometer containing NaI (Tl) detector and a Multichannel Analyzer (MCA). The linear attenuation coefficients have increased with the increasing fiber percentage for all studied gamma energies.
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 705-706
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 116

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