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Peak Energy (peak + energy)
Selected AbstractsPeak energy of the prompt emission of long gamma-ray bursts versus their fluence and peak fluxMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008L. Nava ABSTRACT The spectral-energy (and luminosity) correlations in long gamma-ray bursts are being hotly debated to establish, first of all, their reality against possible selection effects. These are best studied in the observer planes, namely the peak energy Eobspeak versus the fluence F or the peak flux P. In a recent paper, we have started to investigate this problem considering all bursts with known redshift and spectral properties. Here, we consider instead all bursts with known Eobspeak, irrespective of redshift, adding to those a sample of 100 faint BATSE bursts representative of a larger population of 1000 objects. This allows us to construct a complete, fluence-limited, sample, tailored to study the selection/instrumental effects we consider. We found that the fainter BATSE bursts have smaller Eobspeak than those of bright events. As a consequence, the Eobspeak of these bursts is correlated with the fluence, though with a slope flatter than that defined by bursts with z. Selection effects, which are present, are shown not to be responsible for the existence of such a correlation. About six per cent of these bursts are surely outliers of the Epeak,Eiso correlation (updated in this paper to include 83 bursts), since they are inconsistent with it for any redshift. Eobspeak also correlates with the peak flux, with a slope similar to the Epeak,Liso correlation. In this case, there is only one sure outlier. The scatter of the Eobspeak,P correlation defined by the BATSE bursts of our sample is significantly smaller than the Eobspeak,F correlation of the same bursts, while for the bursts with known redshift the Epeak,Eiso correlation is tighter than the Epeak,Liso one. Once a very large number of bursts with Eobspeak and redshift will be available, we thus expect that the Epeak,Liso correlation will be similar to that currently found, whereas it is very likely that the Epeak,Eiso correlation will become flatter and with a larger scatter. [source] Peculiarities of dislocation photoluminescence in germanium with quasi-equilibrium dislocation structurePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2007S. Shevchenko Abstract The dislocation photoluminescence (DPL) at 4.2 K was studied in germanium (Ge) single crystals of n- and p-type with quasi-equilibrium structure of 60° dislocations. The DPL spectra for different samples were decomposed on Gaussian lines (Gm -lines) over the range 0.47-0.58 eV characterized by practically the same peak energies Em and the widths under 15 meV. The G-lines with Em , 0.55 eV were ascribed to the radiation of regular segments of 60° dislocations with different stacking fault (SF) widths , between 30 and 90° partials. An increase of the dislocations density up to ND , 107 cm,2 was found to result in a considerable growth of the intensity of the G-lines with Em <0.513 eV. The factors, which promote the appearance of different , values for quasi-equilibrium 60° dislocation structure, are discussed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Temperature dependence of 2DEG and excitonic optical transitions in AlGaN/GaN heterostructures on SiCPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005C. W. Litton Abstract Four (4) unique optical transitions are reported in both the emission and reflection spectra of high-quality AlGaN/GaN heterostructures. Study of the shifts of spectral peak energies and their intensity variations with temperature, reveal that these transitions arise from Free Exciton recombination and transitions between the A- and B-valence bands and the excited states of the 2-dimensional electron gas (2DEG) at the heterointerface. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] FOOD HARDNESS AND FRACTURABILITY ASSESSMENT BY AN ELECTRONIC SENSING SYSTEM1JOURNAL OF TEXTURE STUDIES, Issue 2 2002YANKUN PENG ABSTRACT Two texture properties of food, hardness and fracturability, were studied by an electronic sensing system (ESS) with 29 cereal-based foods that represented a range of textures. Three electrodes were used with one located on the cheekbone, one on the lower jaw bone, and the other one, a ground, on the ear lobe. Total energy, peak energy, and Fourier power of the first bite ESS signals were analyzed. The Fourier power of the muscle motion in biting was highly correlated to the muscle motion total energy. Sensory hardness and fracturability were correlated with the first bite ESS total energy and first bite ESS Fourier power (r = 0.82 and 0.74). [source] Probing the existence of the Epeak,Eiso correlation in long gamma ray burstsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2005Giancarlo Ghirlanda ABSTRACT We probe the existence of the Epeak,Eiso correlation in long gamma-ray bursts (GRBs) using a sample of 442 BATSE bursts with known Epeak and with redshift estimated through the lag,luminosity correlation. This sample confirms that the rest-frame peak energy is correlated with the isotropic equivalent energy. The distribution of the scatter of the points around the best-fitting line is similar to that obtained with the 27 bursts with spectroscopic redshifts. We interpret the scatter in the Epeak,Eiso plane as due to the opening angle distribution of GRB jets. By assuming that the collimation corrected energy correlates with Epeak we can derive the observed distribution of the jet opening angles, which turns out to be lognormal with a peak value of . [source] Impurity levels in the layered semiconductor p-GaSe doped with group V elements As, Bi and SbPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2005S. Shigetomi Abstract The radiative and non radiative recombination mechanisms in the As, Sb and Bi-doped GaSe have been investigated on the basis of photoluminescence (PL) and Hall effect measurements. The PL features (at 77 K) related to the impurity levels coming from the As, Sb and Bi atoms are dominated by a broad emission band at about 1.7 eV. From the temperature dependences of the peak energy and PL intensity and the dependence of excitation intensity of peak energy, it was found that the 1.7 eV emission band is due to the transition from the shallow donor level at about 0.08 eV below the conduction band to the deep acceptor. In addition it was found, from the temperature dependence of hole concentration, that a deep acceptor level at about 0.6 eV above the valence band is formed by the doping atoms. It is associated with defects or defect complexes. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth and properties of In-rich InGaN films grown on (0001) sapphire by RF-MBEPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2004M. Kurouchi Abstract We have performed detailed investigations of the optical properties of strain-free In-rich InxGa1,xN (0.61 , x , 1.0) films that were grown directly on (0001) sapphire substrates by radio-frequency plasma-excited molecular beam epitaxy. In-composition dependence of photoluminescence peak energy for the InxGa1,xN films, measured at room temperature, exhibited a monotonic and smooth decrease with the increase in the In-composition, approaching to 0.66 eV of a strain-free InN film that was also grown directly on the sapphire substrate. The energy bowing parameter, b was determined to be 1.8 eV using these strain-free InxGa1,xN films. Structural properties of these films are also investigated in detail. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Exciton localization in Al-rich AlGaN ternary alloy epitaxial layersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Hideaki Murotani Abstract Exciton localization in Al-rich AlGaN ternary alloy epitaxial layers has been studied by means of temperature-dependent photoluminescence (PL) spectroscopy. Anomalous temperature dependence of the PL peak energy (red-blue shift) was observed, which enabled us to estimate the localization energy of excitons. The localization energy increased as the 1.2th power of the exciton linewidth. The value of exponent for Al-rich alloys was smaller than that for Ga-rich alloys. This indicated that the excitons in Al-rich alloys were strongly localized compared to that in Ga-rich alloys. In addition, the exponent value for Al-rich alloys increased with increasing excitation power density. This increase in the exponent suggested that the exciton population approached the extended states owing to the saturation of localized states by photo-generated excess excitons. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] RF-MBE growth of InN on 4H-SiC (0001) with off-anglesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Misao Orihara Abstract We have grown InN on 4H-SiC (0001) substrates with various off-angles by RF-N2 plasma molecular beam epitaxy (RF-MBE). Scanning electron microscope observation revealed that InN films grown on 4H-SiC (0001) substrates with off-angles of 4° and 8° are very smooth and that there are no voids which have often observed for InN epitaxial layers. X-ray diffraction reciprocal space maps for InN grown on 4H-SiC (0001) showed that the c-axes of InN grown on 4H-SiC 4° and 8° off substrates are inclined by 0.35° and 0.8°, respectively, toward the misorientation of the substrate while the c-axis of InN is parallel to that of 4H-SiC for the on-axis substrate. Strong PL peak was observed from InN grown on 4° off substrate at 0.68 eV at 15 K. The PL peak was clearly observed even at room temperature and simply shifted to lower energies with increasing temperature. The difference in the PL peak energy between at 15 K and 300 K was 20 meV, which is reasonable taking into account the difference in the thermal coefficients of InN and SiC (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Infrared transient absorption spectra for excited transition of excitons and biexcitons in CuClPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2009Takaaki Yoshioka Abstract Infrared transient absorption (IRTA) spectra for excitons and biexcitons in CuCl bulk crystal have been measured by pump-probe spectroscopy. The IRTA peak energy of the exciton agrees with the transition energy between Rydberg 1s to 2p states reported in one- and two-photon absorption measurement. On the other hand, the IRTA peak energy of the biexcitons locates in energy higher than that of the excitons, which is reasonable by taking hydrogen molecule model into account. In addition, our results support the enhancement of the transition energy between 1s and 2p states in quantum dots compared to the bulk case. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoluminescence of cubic InN films on MgO (001) substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008T. Inoue Abstract We have studied photoluminescence from cubic InN films grown on MgO substrates with a cubic GaN underlayer by RF N2 plasma molecular beam epitaxy. A single PL peak was observed at 0.47 eV. By analyzing the reflectance spectra of cubic InN films, we could derive the refractive index and extinction coefficient, and found the band gap energy of cubic InN is 0.48 eV, indicating that the PL peak observed at 0.47 eV is due to the interband transition of cubic InN. The difference in the PL peak energy between hexagonal and cubic InN is in good agreement with that predicted by ab-initio calculations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoluminescence study of isoelectronic traps in dilute GaAsN alloysPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007H. Yaguchi Abstract We have studied photoluminescence spectra in detail to clarify the character of the isoelectronic traps in dilute GaAsN alloys. Several sharp lines have been observed at the lower energy side of the GaAs bandgap and are in good agreement with the nitrogen pair-related emission lines previously reported. In addition to the nitrogen pair-related lines, some other emission lines have been also observed. Compared with the energies of these emission lines and the nitrogen pair-related emission lines, it was found that the energy differences agree with the longitudinal optical phonon energy at the , point of GaAs, showing that the character of isoelectronic traps due to nitrogen pairs in dilute GaAsN alloys is significantly contributed from the conduction band state at the , point. The temperature dependence of the peak energy of luminescence due to nitrogen pairs also indicates that the character of isoelectronic traps in dilute GaAsN alloys is due to the conduction band edge state at the , point of GaAs. For a dilute GaAsN alloy with lower nitrogen concentration, we have observed that the intensity of an emission line increased superlinearly with excitation power . (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Time-resolved photoluminescence and steady-state optical studies of GaInNAs and GaInAs single quantum wellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007Y. Sun Abstract Time-resolved photoluminescence spectroscopy is used to investigate carrier dynamics of Ga1,xInxNyAs1,y (x , 0.33, y , 0.01) single quantum well (QW) structures. PL spectra measured as a function of temperature together with the PL decay times at wavelengths around and below the PL peak energy are used to determine de-trapping activation energies and time constants. The results are interpreted in terms of simultaneous thermal excitation of deep localized excitons to shallow localized states. According to the model, with increasing temperatures, localized excitons gain enough thermal energy to populate the free exciton states in quantum well with shorter lifetimes due to coherent nature of free excitons. In addition, at temperatures around and above 80 K, more non-radiative channels become available to compete with the radiative processes leading to shorter time constants. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] NH3/TMI molar ratio dependence of electrical and optical properties for atmospheric-pressure MOVPE InNPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006A. Yamamoto Abstract The electrical and optical properties for atmospheric-pressure MOVPE InN have been studied as a function of NH3/TMI molar ratio during the growth. Residual carrier (electron) concentration is decreased with increasing NH3/TMI molar ratio. PL peak energy is also shifted to a low energy side with increasing NH3/TMI molar ratio. Hall mobility of InN is almost independent on NH3/TMI molar ratio and is rather decreased at a high NH3/TMI molar ratio. The highest mobility is obtained for a sample grown at a relatively low NH3/TMI molar ratio. The grain size of the InN films is decreased with increasing NH3/TMI molar ratio. The lowest carrier concentration of 4.5×1018 cm,3 and highest mobility of 1100 cm2/Vs obtained here are the best data for MOVPE InN ever reported. Based on these results, the most probable candidate for donors and the dominant carrier-scattering mechanism for atmospheric-pressure MOVPE InN are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hydrogenation of strain engineered InAs/InxGa1,x As quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2004D. Ochoa Abstract InxGa1,xAs/InAs/InxGa1,xAs structures have been grown by atomic layer molecular beam epitaxy on top of a GaAs buffer and substrate. In these structures, the thickness d and/or the In composition x of the lower InxGa1,xAs confining layer control the strain in self-assembled quantum dots. This strain engineering has allowed achieving emission energies as low as 1.5 ,m at low T, with a rapid quenching of the photoluminescence (PL) signal at high T. Hydrogen irradiation of these structures leads to an increase in the PL efficiency, higher in samples with higher x, with a blue shift in the peak energy. A higher concentration of non radiative defects in confining layers richer in indium is responsible for the observed PL quenching, more than an increased thermal escape of carriers toward the InxGa1,xAs barriers. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improvement of the optical properties of GaN epilayers on Si(111): Impact of GaAs layer thickness on Si and pre-growth strategyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Bablu K. Ghosh Abstract This paper reports the effect of the GaN coating layer on the optical properties of GaN epilayers grown on GaAs/Si(111). Almost crack free GaN epilayers are found to be grown when a thin (,25 nm) GaN coating layer is inserted on 0.5 and 2 ,m GaAs layers at 550 °C. Then nitridation of the GaAs layer is done through the coating layer by NH3 flow while the substrate temperature is ramped at 1000 °C for epilayer growth. An attempt has also been made by implementing an additional GaN interlayer at 800 °C while growth is continued for epilayer growth. For this growth strategy, cracks also happened without improvement of the epilayer quality. PL measurements show high excitonic peak energy and high excitonic to yellow band intensity ratio for GaN epilayers grown on the 0.5 ,m GaAs converted layer (CL) using a thin GaN coating layer. Those values are also found to be comparable/ better than for epilayers grown on 2 ,m CL. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Polarization controlled edge emission from columnar InAs/GaAs self-assembled quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2003T. Kita Abstract Polarization anisotropy of photoluminescence (PL) from the cleaved edge surface of columnar InAs/GaAs self-assembled quantum dots (QDs) has been investigated. The columnar QDs were fabricated by closely stacking the Stranski-Krastanov-mode InAs-island layers. PL peak energy and anisotropy of the PL polarization sensitively depends on the stacking layer number. Whereas the single-island-layer sample shows strong transverse-electric (TE)-mode PL, the PL-intensity ratio of TE-mode PL to transverse-magnetic (TM)-mode PL decreases with increasing stacking layer number. The polarization inversion of TE/TM-mode PL-intensity ratio has been accomplished beyond the stacking layer number of 9. The polarization spectra of the columnar QDs with >9 stacking layers indicate that TM-mode becomes dominant near the ground state transition. [source] | ||||||||||||||||||||||