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  1. 93 Acta Physica Polonica A

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1
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Luminescence Properties of Europium in Sorbates of the Complexes with Naphthoic Acid on Zeolite

100%
Beltyukova S., Egorova A., Tselic E., Teslyuk O.
Acta Physica Polonica A
|
1999
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vol. 95
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issue 6
977-982
EN
A study of luminescence properties of sorbates of the europium(III) complexes with naphthoic acid and 1,10-phenanthroline on the zeolite of CaA-type that may be used as luminophores of the red color luminosity, has been performed. It was shown that the highest luminescence intensity in sorbate is observed upon the preliminary sorption of Eu(III) ion on zeolite following the treatment of naphthoic acid and 1,10-phenanthroline. The stability of sorbates to the temperature action was established (100°C, 2 h).
2
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Quantum Efficiency of the Luminescence of Ytterbium(III) ß-Diketonates

100%
Meshkova S., Topilova Z., Bolshoy D., Beltyukova S., Tsvirko M., Venchikov V.
Acta Physica Polonica A
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1999
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vol. 95
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issue 6
983-990
EN
The processes of the energy deactivation of electronic excitation in Yb(III) ß-diketonates and their dependence on the nature of ß-diketone and the second ligand as well as the environment and its state (complexes in organic solvents and polymer matrix) were studied. Taking as an example the ytterbium thenoyltrifluoroacetonate, it was shown that the energy losses in the ligand and Yb(III) ion, which is due to the high-frequency vibrations of the central C-H group of the ß-diketone, can lead to the decreased quantum yield of the luminescence. The increase in the medium rigidity causes the decrease in losses in the ligand, but does not affect the deactivation of the Yb(III) ion excited level. In the mix-ligand complexes the second ligand (1,10-phenanthroline) improves the screening of the central ion providing almost full transfer of the energy, absorbed by ligand, to ytterbium ion.
3
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Properties of Excitons in Quantum Dots with a Weak Confinement

63%
Gołasa K., Molas M., Goryca M., Kazimierczuk T., Smoleński T., Koperski M., Golnik A., Kossacki P., Potemski M., Wasilewski Z., Babiński A.
Acta Physica Polonica A
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2013
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vol. 124
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issue 5
781-784
EN
Statistical properties of neutral excitons, biexcitons and trions confined to natural quantum dots formed in the InAs/GaAs wetting layer are reported. The correlation of the trion binding energy and the biexciton binding energy was found. Magnetospectroscopic measurements of the excitons revealed also the correlation of excitonic effective g^* factor of an exciton with the biexciton binding energy. The qualitative picture of the effect of quantum confinement on the observed correlations is presented.
4
Publication available in full text mode
Content available

Optical Properties of InAs Quantum Dots

63%
Willander M., Zhao Q., Jacob A., Wang S., Wei Y.
Acta Physica Polonica A
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2002
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vol. 102
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issue 4-5
567-576
EN
InAs quantum dots grown on GaAs substrate were investigated by optical spectroscopy. We particularly emphasized on the photoluminescence intensity, the stability of the photoluminescence intensity versus temperatures and wavelength of the InAs dot emission at various thermal treatments and different structures. We found that hydrogen can strongly passivate nonradiative centers without causing any structure degradation, and both n- and p-type modulation doping can reduce the decrease in the photoluminescence intensity when the sample temperature increases from the helium temperature to room temperature. The emission wavelength and the efficiency of the InAs quantum dots can also be manipulated by choosing proper materials of cap layer.
5
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Solid-State Cavity Quantum Electrodynamics Using Quantum Dots

63%
Gérard J., Gayral B., Moreau E., Robert I., Abram I.
Acta Physica Polonica A
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2001
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vol. 100
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issue 2
129-143
EN
We review the recent development of solid-state cavity quantum electrodynamics using single self-assembled InAs quantum dots and three-dimensional semiconductor microcavities. We discuss first prospects for observing a strong coupling regime for single quantum dots. We then demonstrate that the strong Purcell effect observed for single quantum dots in the weak coupling regime allows us to prepare emitted photons in a given state (the same spatial mode, the same polarization). We present finally the first single-mode solid-state source of single photons, based on an isolated quantum dot in a pillar microcavity. This optoelectronic device, the first ever to rely on a cavity quantum electrodynamics effect, exploits both Coulomb interaction between trapped carriers in a single quantum dot and single mode photon funneling by the microcavity.
6
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Effect of Hydrostatic Pressure on InP:Yb Luminescence

63%
Stąpor A., Kozanecki A., Reimann K., Syassen K., Weber J., Moser M., Scholz F.
Acta Physica Polonica A
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1991
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vol. 79
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issue 2-3
315-318
EN
Tle effects of hydrostatic pressure on the InP:Yb luminescence were explored using a gasketed diamond anvil cell (DAC). The pressure dependence of the Yb^{3+} luminescence shows a small positive shift (0.96 meV/GPa) at low pressures (< 4 GPa) and a negative one (-0.04 meV/GPa) above 4 GPa. The spectra of the Yb^{3+} emission differ markedly in these two pressure ranges. It was concluded that intra-4f-shell transitions of the Yb^{3+} on indium substitutional (Td) site dominate in the spectrum above 4 GPa, whereas at lower pressures the emission has a different nature.
7
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Time Evolution of the Microluminescence Energy οf GaN/AlGaN Quantum Dots

63%
Surowiecka K., Wysmołek A., Stępniewski R., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
933-935
EN
Time evolution of the microphotoluminescence from low-density GaN/Al_{x}Ga_{1-x}N quantum dots grown by metal organic chemical vapor deposition using in situ etching of AlGaN is presented. The observed effect is related to the energy changes that begin immediately after sample illumination with the exciting laser light and saturate after some time. Typically, the luminescence energy decreases and the change is exponential with characteristic times in a range between several dozen and several hundred seconds. However, sometimes we observed the energy increase with characteristic times in a range between several and a few hundred seconds. The obtained results are discussed in terms of the metastable change of the electric field, induced by spontaneous polarization present in GaN/AlGaN structure (in the growth direction), and strain- or defect-induced changes of the electric field in the vicinity of the dot.
8
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Fine Structure of the Localized Emission from GaInNAs Layers Studied by Micro-Photoluminescence

63%
Kudrawiec R., Latkowska M., Sęk G., Misiewicz J., Ibáñez J., Henini M., Hopkinson M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
930-932
EN
GaInNAs bulk-like layers ( ≈ 20% In and ≈ 3% N) grown on GaAs substrate with various crystallographic orientations have been studied by micro-photoluminescence at low temperatures for a broad range of excitation conditions. In addition to photoluminescence peaks, which are associated with heavy- and light-hole free exciton recombination, a band of sharp lines was observed below the fundamental free exciton transition at low excitation. It shows that the localized emission which is typical of this alloy at low temperatures is composed of individual narrow photoluminescence lines which are associated with the recombination of single excitons. They can be localized on various local potential minima including those originating from the alloy content fluctuations and/or deep acceptor(donor)-like complexes.
9
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Optical Properties of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} Epitaxial Layers

63%
Świątek K., Piskorski M., Piotrowski T.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
1100-1102
EN
Photoluminescence spectra of Al_{x}Ga_{1-x}As_{y}Sb_{1-y} layers (x = 0.2-0.5, y = 0.02-0.03) grown by liquid-phase epitaxy on GaSb substrates were studied in a wide temperature range (14-295 K). The temperature changes of energy and intensity of the layer and substrate emission were measured. Linear part of the temperature-induced energy shift of the Al_{0.20}Ga_{0.80}As_{0.02}Sb_{0.98} band-to-band emission exhibits a slope of -0.3 meV/K and -0.45 meV/K at temperatures 150 K and 295 K, respectively.
10
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Two-Electron Transition in Homoepitaxial GaN Layers

63%
Fiorek A., Baranowski J., Wysmołek A., Pakuła K., Wojdak M., Grzegory I., Porowski S.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
742-744
EN
It is shown that the luminescence mapping is a powerful method to help identify optical transitions. Two-electron transition was identified in the homoepitaxial GaN layer by this technique. It was found that the donor and acceptor bound exciton emissions are spatially displaced and show intensity maxima at different places of the epitaxial layer. It was also found that the 3.45 eV line, suspected as "two-electron transition", follows exactly the donor bound exciton spatial distribution. Donor bound exciton recombines leaving the neutral donor in the excited 2s state. Thus, 1s-2s excitation being equal to 22 meV corresponds to 29 meV hydrogenic donor binding energy. This is the first identification of the two-electron transition in GaN.
11
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Hydrostatic Pressure Spectroscopy of the Vanadium Luminescence in GaAs

63%
Wysmołek A., Bożek R., Babiński A., Hennel A.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
837-840
EN
We report luminescence measurements of the intracenter transition ^{3}T_{2} → ^{3}A_{2} of the V^{3+}(3d^{2}) charge state in semi-insulating GaAs under hydrostatic pressure up to 0.8 GPa at liquid helium temperature. The hydrostatic pressure coefficient of the zero-phonon line is found to be equal to 6.9 ± 0.2 meV/GPa. This result enables us to determine the Huang-Rhys parameter, which characterizes the coupling to the symmetric mode of vibration, as S_{A} = 1.4 ± 0.1. Using this parameter, computer simulation leading to a reconstruction of the shape of both luminescence and corresponding absorption spectra were performed.
12
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Influence of Electric Field and Carrier Localization on Carrier Dynamics in AlGaN Quantum Wells

63%
Mickevičius J., Tamulaitis G., Kuokštis E., Shur M., Yang J., Gaska R.
|
EN
Dynamics of nonequilibrium carriers in high-Al-content AlGaN/AlGaN multiple quantum wells was studied. A set of multiple quantum wells with well widths varying from 1.65 to 5.0 nm was grown by metal-organic chemical vapor deposition. The structures were investigated by photoluminescence spectroscopy under quasi-steady-state conditions. The observed blueshift of the photoluminescence band peak was attributed to the screening of the built-in electric field. The integrated photoluminescence intensity dependence on excitation and temperature showed a strong influence of carrier localization.
13
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Real-Space Mapping of Exciton Wave Functions in a Quantum Dot with Near-Field Optical Imaging Spectroscopy

63%
Saiki T., Matsuda K., Nomura S., Mihara M., Aoyagi Y., Nair S., Takagahara T.
Acta Physica Polonica A
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2003
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vol. 104
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issue 3-4
281-287
EN
An exciton confined within a quantum dot acts as a two-level quantum system, and is one of the most promising candidates for quantum computing and quantum information processing. The real-space optical probing of the quantum eigenstates in a single quantum dot and coupled quantum dots should be developed toward the realization of quantum photonic devices, where their wave functions are dynamically controlled by coherent optical techniques. Here we apply near-field photoluminescence imaging spectroscopy with a high spatial resolution of 30 nm to map out the centre-of-mass wave function of an exciton confined in a GaAs quantum dot. The spatial profile of the exciton emission, which reflects the shape of a monolayer-high island, differs from that of biexciton emission, due to different distributions of the polarization field for the exciton and biexciton recombinations.
14
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Growth of GaN Metalorganic Chemical Vapour Deposition Layers on GaN Single Crystals

63%
Pakula K., Baranowski J. M., Stępniewski R., Wysmołek A., Grzegory I., Jun J., Porowski S., Sawicki M., Starowieyski K.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
861-864
EN
The homoepitaxial growth of GaN layers has been achieved for the first time. Bulk GaN single crystals which have been used as a substrate have been grown from diluted solution of atomic nitrogen in the liquid gallium at 1600°C and at nitrogen pressure of about 15-20 kbar. It is shown that a terrace growth of GaN epitaxial layer has been realized. The high quality of the GaN film has been confirmed by luminescence measurements. The analysis of donor-acceptor and exciton luminescence is presented.
15
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Content available

Magneto-Optical Studies of Quantum States of Two-Dimensional Hole Gas at Single Ga_{1-x}Al_xAs/GaAs Heterojunction

63%
Bryja L.
Acta Physica Polonica A
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2004
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vol. 106
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issue 2
131-140
EN
The detailed studies of low temperature (T=2~K) polarization resolved photoluminescence and photoluminescence excitation studies from heavily modulation doped Ga_{1-x}Al_xAs/GaAs single heterojunctions in continuous wave and time-resolved conditions are reported. The free conduction band GaAs electrons recombination with two-dimensional holes observed in low magnetic fields enabled us to determine experimentally the valence subband Landau levels. The high magnetic field photoluminescence spectra are dominated by excitonic transitions which are attributed to neutral excitons rather than to positively charged ones.
16
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Optical Processes in Quantum Wells

63%
Sham L. J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
7-15
EN
A review is given of the theoretical framework of exciton dynamics in quantum wells including the spin degrees of freedom. A study is made of various momentum, energy, and spin relaxation mechanisms including the effects of exciton-phonon interaction, the single-particle spin-flips by means of spin-orbit interaction and the exciton spin-flip by means of the exchange interaction. All these competing mechanisms are taken into account in a set of equations governing the time evolution of the exciton spin populations. Solutions are then used to interpret observed time-resolved observations of polarized luminescence spectra. For excitons in a two-dimensional system such as a semiconductor quantum well, the breaking of the translational symmetry in the direction normal to the interface plane has been shown theoretically by Hanamura, by Andreani and Bassani, and by Citrin to result in a recombination rate much faster than in a three-dimensional system. Yet, experiments show comparable decay rates in two- and three-dimensional excitons. Recent experiments with high time resolutions show two decay times for the total luminescence intensity. The slower one agrees with the one usually observed and interpreted as the radiative recombination time. We shall give an explanation for the fast decay as a combination of radiative recombination and single-particle spin-flip and for the slow decay as the radiative recombination slowed down by the presence of lower energy dark states for excitons with parallel spins. The ability to use the same theory to account for the polarization behavior confirms the importance of the exciton spin dynamics. Furthermore, the longitudinal electric field dependence is used to check our theory of exchange.
17
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Temporal Evolution of Multi-Carrier Complexes in Single GaN/AlGaN Quantum Dots

63%
Surowiecka K., Wysmołek A., Stępniewski R., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
879-884
EN
Microphotoluminescence of low-density GaN/Al_xGa_{1-x}N quantum dots grown by metal-organic vapor phase epitaxy using in situ etching of AlGaN is presented. The narrow lines in the microphotoluminescence spectra due to the single quantum dots are observed. Both energy and intensity of these lines show temporal fluctuations. Statistical analysis based on the correlation matrix allowed us to identify objects, which are affected by photo-induced electric field fluctuations. Relations between emission lines participating in the spectrum are discussed.
18
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Electron Spins in Self-Assembled (In,Ga)As/GaAs Quantum Dots Studied by Pump-Probe Faraday Rotation

63%
Greilich A., Yugova I., Oulton R., Zhukov E., Yakovlev D., Bayer M., Shabaev A., Efros A., Stavarache V., Reuter D., Wieck A.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
287-293
EN
Static and dynamic properties of electron spins in self-assembled (In,Ga)As/GaAs quantum dots which contain on average a single electron per dot were studied by pump-probe Faraday rotation. Examples given here are the g-factor tensor components as well as the dephasing time T*_2 within a dot ensemble.
19
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Fine Structure of Neutral Excitons in Single GaAlAs Quantum Dots

63%
Molas M., Gołasa K., Piętka B., Potemski M., Babiński A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
988-990
EN
Optical anisotropy of neutral excitons in GaAlAs/AlAs quantum dots is investigated. Low-temperature polarization-sensitive photoluminescence measurements of single quantum dots are performed. It is found that neutral excitons (X) in the quantum dots exhibit a fine structure splitting. The fine structure splitting ranges from 10 μeV to 100 μeV and correlates with the X energy. The polarization axis of the fine structure splitting is well oriented along [110] crystallographic direction of a substrate. The orientation is attributed to the elongation of GaAlAs/AlAs quantum dots in the [110] direction of the substrate.
20
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Single GaN/AlGaN Quantum Dot Spectroscopy

63%
Surowiecka K., Wysmołek A., Stępniewski R., Bożek R., Pakuła K., Baranowski J.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
233-236
EN
Microphotoluminescence of low-density GaN/Al_{x}Ga_{1-x}N quantum dots grown by metal-organic vapor phase epitaxy using in situ etching of AlGaN is presented. The detailed analysis of the emission from these structures enables the observation of pairs of lines separated by the energy up to 3 meV. They behave in a different way under different excitation power that suggests that this doublet structure can be associated with the exciton and trion (or biexciton recombination). It is observed that for different quantum dots the energy of the charged exciton complex emission could be higher or lower than the neutral exciton one. It is discussed in terms of a competition between attractive e-h and repulsive e-e (h-h) Coulomb interaction that occurs because of the existence of the built-in electric field that separates electrons and holes in the dot.
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