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Wyświetlanie 1-6 z 6
Tytuł:
Luminescence Spectra of ZnAl$\text{}_{2}$O$\text{}_{4}$:Cr$\text{}^{3+}$ Spinel Nanopowders
Autorzy:
Luc, H. H.
Nguyen, T. K.
Nguyen, V. M.
Suchocki, A.
Kamińska, A.
Le, V. K.
Nguyen, V. H.
Luong, T. T.
Powiązania:
https://bibliotekanauki.pl/articles/2037040.pdf
Data publikacji:
2003-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.60.-b
72.80.Ga
81.05.Je
81.05.Mh
Opis:
The synthetic ZnAl$\text{}_{2}$O$\text{}_{4}$ spinels doped with Cr$\text{}^{3+}$ ions are prepared from ZnSO$\text{}_{4}$, Al$\text{}_{2}$(SO$\text{}_{4}$)$\text{}_{3}$, and Cr$\text{}_{2}$(SO$\text{}_{4}$)$\text{}_{3}$. The spinel single phase is detected from X-ray diffraction. Luminescence properties of Cr$\text{}^{3+}$ in ZnAl$\text{}_{2}$O$\text{}_{4}$ were studied by low temperature luminescence and decay measurements. Four luminescence lines at 14570, 14520, 14460, and 14330 cm$\text{}^{-1}$ were found to originate from structure distortion and the line at 14175 cm$\text{}^{-1}$ - from chromium pairs. The broad emission band at about 13540 cm$\text{}^{-1}$ is considered to arise from a new Cr$\text{}^{3+}$ center in ZnCr$\text{}_{2}$O$\text{}_{4}$.
Źródło:
Acta Physica Polonica A; 2003, 104, 6; 581-587
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physics of Neutral-to-Ionic Phase Transition in Organic Charge Transfer Semiconducting Compounds
Autorzy:
Cailleau, H.
Lemée-Cailleau, M. H.
Le Cointe, M.
Luty, T.
Powiązania:
https://bibliotekanauki.pl/articles/1967953.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.38.+i
61.50.Ks
71.35.Aa
Opis:
An uncommon excitonic instability takes place in some exotic semiconducting compounds. Indeed, the equilibrium neutral-to-ionic (N-I) phase transition, as well as the non-equilibrium photo-induced phase transformation, observed in some organic charge-transfer complexes, originate from intra- and inter-chain cooperative effects between structurally relaxed charge-transfer excitations. This electronic-structural phase transition manifests itself by a change of the degree of charge-transfer and a dimerization distortion with the formation of donor-acceptor pairs along the stacking axis in the I phase. Thermal charge-transfer excitations associated with the formation of I strings along N chains are at the heart of the mechanism of this phase transition. These relaxed electronic excitations, which are an intrinsic feature of low-dimensional systems with strong electron-phonon coupling, can be described in terms of self-trapping and self-multiplication of charge-transfer excitons. Precise structural studies on the prototype compound, tetrathiafulvalene-p-chloranil allow to highlight the respective role taken by the ionicity and the dimerization. Symmetry and thermodynamics analysis of the N-I transition, based on recent determination of the pressure-temperature phase diagram, make possible to present a consistent picture of this phase transition. Supported by theoretical considerations taking into account the interplay between quantum and thermal effects, the experimental observations show that the N-I transition results from the condensation and the ordering (crystallization) of charge-transfer excitations, following a phase diagram analogous to the solid-liquid-gas one.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 597-608
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High-Pressure Study of $Gd_2(MoO_4)_3$ by Raman Scattering and Ab Initio Calculations
Autorzy:
Lucazeau, G.
Bouvier, P.
Pasturel, A.
Le Bacq, O.
Pagnier, T.
Powiązania:
https://bibliotekanauki.pl/articles/1807798.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.50.Ks
64.70.K-
71.15.Mb
78.30.-j
Opis:
High-pressure induced phase transitions in a single crystal of gadolinium molybdate, $Gd_2(MoO_4)_3$ were studied by the Raman spectroscopy and ab initio calculations. The amorphization of the sample takes place at about 6 GPa in a mixture of alcohol as a pressure transmitting medium and begins as soon as 3 GPa in argon. In both media, the amorphization is irreversible in the 0-9 GPa investigated pressure range. The joint ab initio and Raman results allowed us to conclude that rotations of $MoO_4$ tetrahedra are the primary structural changes involved in the first phase transition (at about 2 GPa) explaining the softening of the low frequency modes at about 50 $cm^{-1}$. In addition, a progressive distortion of tetrahedra followed by a coordination change (IV-VI) of Mo atoms is observed through the five structural transitions including amorphization. This mechanism based on the steric hindrance of polyhedra is believed to be the most relevant for explaining the amorphization of $Gd_2(MoO_4)_3$.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 25-31
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photovoltaic Effect on PbTe p-n Junction in the Presence of Magnetic Field
Autorzy:
Le Van, Khoi
Grodzicka, E.
Witkowska, B.
Story, T.
Gałązka, R. R.
Powiązania:
https://bibliotekanauki.pl/articles/1929738.pdf
Data publikacji:
1993-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.25.Tn
78.20.Ls
72.80.Ga
Opis:
Photovoltaic spectra of PbTe p-n junction have been measured in the infrared spectral region in the temperature range of 8-260 K. The p-n junctions have been formed by cadmium diffusion into the p-type PbTe crystals. From the positions of the photovoltaic maxima the energy gap of the diode material has been determined. In the presence of a magnetic field up to 7 T, a pronounced oscillatory behavior of the photovoltage was observed in the Faraday and Voigt configurations. Experiments were performed as a function of the magnetic field intensity at a constant wavelength of the incident light. The energy of the interband magnetooptical transitions between the Landau levels in PbTe was determined and compared with the theoretical model of Adler, describing the energy band structure for the IV-VI compounds.
Źródło:
Acta Physica Polonica A; 1993, 84, 4; 721-724
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
PIPT from the Beginning to Future
Autorzy:
Cailleau, H.
Luty, T.
Koshihara, S.
Servol, M.
Lorenc, M.
Buron-Le Cointe, M.
Collet, E.
Powiązania:
https://bibliotekanauki.pl/articles/1489952.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
64.70.K-
78.47.D-
Opis:
The birth of the field of photoinduced phase transitions was strongly influenced by the conceptual viewpoint expressed by Professor Y. Toyozawa on the condensation of relaxed excitons. Since this first period, twenty years ago, this young field has been expanding rapidly along a diversity of directions. Nowadays, it goes hand in hand with the challenges of today's science: emergence, nonlinearity, coherence, far away from equilibrium, for example. The control of the functionality of a material via photoexcited states poses many new fundamental questions. Some of them will be overviewed: (i) the nature of the control parameters and the nature of the relevant collective variables, especially the order parameters, which characterize the evolution of the system, (ii) the difference between photoinduced transformations under continuous light irradiation and those resulting from an ultrashort laser pulse, (iii) the physical mechanisms of ultrafast photoinduced phase transitions from the formation and proliferation of phototransformed entities to the softening of a collective mode.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 297-306
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
From Light to Heavy Nuclear Systems, Production and Decay of Fragments Studied with Powerful Arrays
Autorzy:
Casini, G.
Morelli, L.
Barlini, S.
Piantelli, S.
D'Agostino, M.
Baiocco, G.
Marchi, T.
Abbondanno, U.
Ademard, G.
Appannababu, S.
Bini, M.
Bonnet, E.
Borderie, B.
Bougault, R.
Bruno, M.
Chbihi, A.
Cinausero, M.
Degerlier, M.
Fabris, D.
Frankland, J.
Gelli, N.
Gramegna, F.
Gruyer, D.
Gulminelli, F.
Kordyasz, A.
Kozik, T.
Kravchuk, V.
Kulig, P.
Le Neindre, N.
Lopez, O.
Maurenzig, P.
Olmi, A.
Pasquali, G.
Pârlog, M.
Poggi, G.
Rivet, M.
Rosato, E.
Sosin, Z.
Spadaccini, G.
Stefanini, A.
Twarog, T.
Valdrè, S.
Vient, E.
Raduta, A.
Powiązania:
https://bibliotekanauki.pl/articles/1402639.pdf
Data publikacji:
2015-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
25.70.Gh
25.70.Pq
25.70.Mn
29.40.-n
Opis:
Reactions between heavy-ions at various energy regimes produce many nuclear fragments which can be populated in highly excited states. The study of these fragments, detected at the end of their particle decay, is important to investigate nuclear forces and structure effects. In recent years there have been many efforts to extend these studies towards the drip-lines, i.e. to systems far from the β-stability valley, by using accelerated radioactive beams. The development of such infrastructures is accompanied by the development of more powerful detectors and associated electronics, capable to identify ions with very different sizes and kinetic energies. Here we give two examples which show how advanced arrays can contribute to the studies on nuclear phenomena. The examples come from the European FAZIA collaboration and from recent campaigns with the GARFIELD apparatus, the latter in operation at the INFN Legnaro Laboratory (Italy) where the SPES RIB facility is under construction.
Źródło:
Acta Physica Polonica A; 2015, 127, 5; 1548-1551
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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