Single Broad Line Research Articles

Subrelativistic Outflow and Hours-timescale Large-amplitude X-Ray Dips during Super-Eddington Accretion onto a Low-mass Massive Black Hole in the Tidal Disruption Event AT2022lri

We present the tidal disruption event (TDE) AT2022lri, hosted in a nearby (≈144 Mpc) quiescent galaxy with a low-mass massive black hole (104 M ⊙ < M BH < 106 M ⊙). AT2022lri belongs to the TDE-H+He subtype. More than 1 Ms of X-ray data were collected with NICER, Swift, and XMM-Newton from 187 to 672 days after peak. The X-ray luminosity gradually declined from 1.5 × 1044 erg s−1 to 1.5 × 1043 erg s−1 and remains much above the UV and optical luminosity, consistent with a super-Eddington accretion flow viewed face-on. Sporadic strong X-ray dips atop a long-term decline are observed, with a variability timescale of ≈0.5 hr–1 days and amplitude of ≈2–8. When fitted with simple continuum models, the X-ray spectrum is dominated by a thermal disk component with inner temperature going from ∼146 to ∼86 eV. However, there are residual features that peak around 1 keV, which, in some cases, cannot be reproduced by a single broad emission line. We analyzed a subset of time-resolved spectra with two physically motivated models describing a scenario either where ionized absorbers contribute extra absorption and emission lines or where disk reflection plays an important role. Both models provide good and statistically comparable fits, show that the X-ray dips are correlated with drops in the inner disk temperature, and require the existence of subrelativistic (0.1–0.3c) ionized outflows. We propose that the disk temperature fluctuation stems from episodic drops of the mass accretion rate triggered by magnetic instabilities or/and wobbling of the inner accretion disk along the black hole’s spin axis.

Photoluminescence Properties of InAs Quantum Dots Overgrown by a Low-Temperature GaAs Layer under Different Arsenic Pressures

We studied the influence of the arsenic pressure during low-temperature GaAs overgrowth of InAs quantum dots on their optical properties. In the photoluminescence spectrum of quantum dots overgrown at a high arsenic pressure, we observed a single broad line corresponding to unimodal size distribution of quantum dots. Meanwhile, two distinct peaks (~1080 and ~1150 nm) at larger wavelengths are found in the spectra of samples with quantum dots overgrown at a low arsenic pressure. We attributed this phenomenon to the high-pressure suppression of atom diffusion between InAs islands at the overgrowth stage, which makes it possible to preserve the initial unimodal size distribution of quantum dots. The same overgrowth of quantum dots at the low arsenic pressure induces intensive mass transfer, which leads to the formation of arrays of quantum dots with larger sizes. Integrated photoluminescence intensity at 300 K is found to be lower for quantum dots overgrown at the higher arsenic pressure. However, a difference in the photoluminescence intensity for the high- and low-pressure overgrowths is not so significant for a temperature of 77 K. This indicates that excess arsenic incorporates into the capping layer at high arsenic pressures and creates numerous nonradiative recombination centers, diminishing the photoluminescence intensity.

Pure shift amide detection in conventional and TROSY-type experiments of 13C,15N-labeled proteins

Large coupling networks in uniformly 13C,15N-labeled biomolecules induce broad multiplets that even in flexible proteins are frequently not recognized as such. The reason is that given multiplets typically consist of a large number of individual resonances that result in a single broad line, in which individual components are no longer resolved. We here introduce a real-time pure shift acquisition scheme for the detection of amide protons which is based on 13C-BIRDr,X. As a result the full homo- and heteronuclear coupling network can be suppressed at low power leading to real singlets at substantially improved resolution and uncompromised sensitivity. The method is tested on a small globular and an intrinsically disordered protein (IDP) where the average spectral resolution is increased by a factor of ~ 2 and higher. Equally important, the approach works without saturation of water magnetization for solvent suppression and exchanging amide protons are not affected by saturation transfer.

Continuous wave and pulsed EPR study of Cd1-xMnxTe crystals with different Mn content

The cadmium manganese telluride (Cd1–xMnxTe) crystals (x &lt; 0.001 and x = 0.02, 0.04, 0.1) grown using the Bridgman method were studied by applying continuous wave and pulsed electron paramagnetic resonance (EPR) spectroscopy in the wide temperature range. The Cd1–xMnxTe crystals with x &lt; 0.001 revealed the EPR spectrum from isolated Mn2+ with g⊥ = g∥ = 2.0074(3), |A⊥| = |A∥| = 56.97 ⋅ 10–4 cm–1, |a| = 30.02⋅10–4 cm–1, while Cd1–xMnxTe crystals with x = 0.02…0.04 are characterized by two single broad isotropic EPR lines of Lorentzian shape (g ~ 2.009 and g ~ 1.99) due to Mn clusters of different sizes. The EPR spectrum of Cd1–xMnxTe crystals with x = 0.01 consists of the single broad line at g ~ 2.01 due to higher level of homogeneity inherent to these crystals. The temperature dependence of spin relaxation times for the isolated Mn2+ center in the Cd1–xMnxTe crystals with x &lt; 0.001 has been described using the conceptions of Orbach process for TM–1 and two-phonon Raman process for T1–1.

The Active Galactic Nuclei in the Hobby–Eberly Telescope Dark Energy Experiment Survey (HETDEX). II. Luminosity Function

We present the Lyα emission line luminosity function (LF) of the active galactic nuclei (AGN) in the first release of the Hobby–Eberly Telescope Dark Energy Experiment Survey (HETDEX) AGN catalog. The AGN are selected either by emission line pairs characteristic of AGN or by a single broad emission line, free of any photometric preselections (magnitude/color/morphology). The sample consists of 2346 AGN spanning 1.88 < z < 3.53, covering an effective area of 30.61 deg2. Approximately 2.6% of the HETDEX AGN are not detected at >5σ confidence at r ∼ 26 in the deepest r-band images we have searched. The Lyα line luminosity ranges from ∼1042.3 to 1045.9 erg s−1. Our Lyα LF shows a turnover luminosity with opposite slopes on the bright end and the faint end: The space density is highest at erg s−1. We explore the evolution of the AGN LF over a broader redshift range (0.8 < z < 3); constructing the rest-frame ultraviolet (UV) LF with the 1450 Å monochromatic luminosity of the power-law component of the continuum (M1450) from M 1450 ∼ −18 to −27.5. We divide the sample into three redshift bins (z ∼ 1.5, 2.1, and 2.6). In all three redshift bins, our UV LFs indicate that the space density of AGN is highest at the turnover luminosity with opposite slopes on the bright end and the faint end. The M 1450 LFs in the three redshift bins can be well fit with a luminosity evolution and density evolution model: the turnover luminosity () increases, and the turnover density (Φ*) decreases with increasing redshift.

The Active Galactic Nuclei in the Hobby–Eberly Telescope Dark Energy Experiment Survey (HETDEX). I. Sample Selection

We present the first active galactic nuclei (AGN) catalog of the Hobby–Eberly Telescope Dark Energy Experiment Survey (HETDEX) observed between 2017 January and 2020 June. HETDEX is an ongoing spectroscopic survey (3500–5500 Å) with no target preselection based on magnitudes, colors or morphologies, enabling us to select AGN based solely on their spectral features. Both luminous quasars and low-luminosity Seyferts are found in our catalog. AGN candidates are selected with at least two significant AGN emission lines, such as the Lyα and C iv λ1549 line pair, or with a single broad emission line with FWHM > 1000 km s−1. Each source is further confirmed by visual inspections. This catalog contains 5322 AGN, covering an effective sky coverage of 30.61 deg2. A total of 3733 of these AGN have secure redshifts, and we provide redshift estimates for the remaining 1589 single broad-line AGN with no crossmatched spectral redshifts from the Sloan Digital Sky Survey Data Release 14 of QSOs. The redshift range of the AGN catalog is 0.25 < z < 4.32, with a median of z = 2.1. The bolometric luminosity range is 109–1014 L ☉ with a median of 1012 L ☉. The median r-band magnitude of our AGN catalog is 21.6 mag, with 34% having r > 22.5, and 2.6% reaching the detection limit at r ∼ 26 mag of the deepest imaging surveys we searched. We also provide a composite spectrum of the AGN sample covering 700–4400 Å.

Novel VO (IV) complexes derived from a macrochelates: Synthesis, characterization, molecular modeling and in vivo insulin‐mimic activity studies

For the development of extensive investigations into a potential medicinal application of vanadium coordination compounds for the oral treatment of diabetes, new mono and bimetallic VO (IV) complexes with N,N′‐(2,2′‐(9,10‐dihydro‐9,10‐ethanoanthracene‐11,12‐dicarbonyl) bis (hydrazine‐1‐carbonothioyl)) dibenzamide (H6EBT) and 2,2′‐((9S,10S,11R,12R)‐9,10‐dihydro‐9,10‐ethanoanthracene‐11, 12‐dicarbonyl) bis (N‐phenylhydrazine‐1‐carboxamide) (H6EPH) have been isolated and characterized. The FTIR and NMR spectral data revealed that H6EBT acts as neutral tridentate and dibasic hexadentate while H6EPH as dibasic tridentate and tetrabasic hexadentate. The electronic and ESR spectra indicated that complexes has octahedral geometry. ESR spectrum of [(VO)(H6EBT)(SO4)].5H2O gives a well resolved hyperfine eight‐line pattern typical spectrum for mononuclear vanadyl complexes with g˃ g⊥ = 1.9 suggesting that the ligand donor atoms ONS are coplanar with the two chelate rings forming octahedral geometry. Also, the high parallel hyperfine splitting value, A = 0.0108, than perpendicular one (A⊥ = 0.0087) indicated that the single d‐ electron is in a σ‐nonbonding orbital and aiming away from the equatorial ligands. On the other hand, the EPR spectra of the binuclear [(VO)2(H4EBT)(SO4)]3H2O and [(VO)2(H2EPH)(H2O)2].10H2O complexes gave a single broad line centered at g = 2.05 and 2.07, respectively, without resolved hyperfine structure paramagnetic triplet (S = 1) is consistent with the anomalous value of the magnetic moment value (μeff = 1.100 and 0.99 B.M.) supporting a binuclear nature. The TG analyses confirmed the existence of solvent molecules inside and/or outside the coordination sphere. The DFT molecular modeling of ligands and its VO (IV) complexes supported the suggested geometries. Also, all compounds were screened for in vivo insulin‐mimetic activity.

Correlation between parotid saliva composition and dental caries using 31P-NMR and ICDAS score

ObjectivesThe preservation of enamel mineral is influenced by the supersaturation of salivary secretions with respect to calcium phosphate salts. The aim was to measure the chemical environmental state of phosphate ions in a subject’s parotid saliva, and to correlate this with their dental caries score, by means of 31P-Nuclear Magnetic Resonance Spectroscopy (31P-NMR) and the International Caries Detection and Assessment System (ICDAS). DesignUnilateral paraffin wax stimulated parotid saliva samples were collected from 21 healthy adult subjects using a Lashley cup. The flowrate was recorded during collection. Clinical caries scores of each subject were classified using the ICDAS score. The pH was recorded for each saliva sample. 31P-NMR spectra of each saliva sample were obtained to determine the phosphorus chemical environment. All the collected data were analysed by Pearson’s correlation. ResultsParotid saliva flow rates were in the range from 0.07 to 0.56 ml/min. The pH varied from 5.9 to 7.6. Each 31P-NMR spectrum showed a single broad line with a chemical shift between 0.07 and 2.38 ppm. At neutral pH the maximum chemical shift was 2.05 ppm, whereas at a lower pH values the phosphorous chemical shift reduced, to 0.34 at pH 5.9. The flowrate and the 31P-NMR chemical shift correlated positively (r = 0.71; p < 0.05). The ICDAS score correlated negatively with the 31P-NMR chemical shift (r = 0.43; p < 0.05). ConclusionsThis parotid saliva 31P-NMR study has shown that different phosphate states exist within saliva, which significantly influence its inorganic chemical behaviour, and therefore its cariostatic activity.

The Impact of Electron Beam Irradiation in Topaz Quality Enhancement

Most of the natural topaz is found as colorless. Variety attempt have been used to change its color. In this study, the process of enhancement by electron irradiation be carefully taken by consideration on the optimization of power and energy of electron, efficient cooling system, annealing process and radioactivity occurring and remaining. Electron irradiation was performed on topaz originated from Yen Bai province, in Vietnam. The two of topaz sample were irradiated by 20 MeV electron beam (e-beam) with different fluences of 1.34×1016 cm−2 and 2.64×1016 cm−2, respectively. The characteristic spectra obtained from the investigation compared to the natural topaz sample afterwards. Interaction of radiation with impurity ions in topaz sample during irradiation resulted in changing of colorless to sky blue topaz, which had the broad absorption band of UV-Vis spectroscopy at 620 nm. The ESR spectrum of topaz sample showing a single broad isotropic line with g = 2.012 that are correlated with an O-center in the topaz structure. FTIR spectra indicated that sky blue color may originate from the decomposition of hydroxyl group (OH) by the electron beam irradiation.

Electron Paramagnetic Resonance in HoxLu1−xB12 Dodecaborides

The high-frequency (60 GHz) electron paramagnetic resonance is studied in HoxLu1−xB12 single crystals at low temperatures (2–80 K) in an applied magnetic field up to 7 T within a wide doping range, 0.01 ≤ x ≤ 1. These compounds are characterized by the presence of a low-temperature cage glass phase with random displacements of magnetic holmium ions from the centrosymmetric position in B12 boron cuboctahedra. For the samples with x ≥ 0.1, it is demonstrated that the electron paramagnetic resonance in the form of a single broad line with a g-factor of about 5 appears in the cage glass phase at T 0.3, the pronounced broadening of the resonance line and a steep decrease in the g-factor related to antiferromagnetic correlations is observed on cooling at T < 30 K. The performed simulation of the electron paramagnetic resonance spectra suggests the dominant role of the exchange interaction effects and positional disorder in determining the characteristic features of spin dynamics in HoxLu1−xB12.

Evidence of surface spin-glass behavior in NiFe2O4 nanoparticles determined using magnetic resonance technique

Abstract Nanosized nickel ferrite (NiFe2O4) is successfully synthesized by the sol-gel method using citric acid (C6H8O7) as fuel. The X-ray diffraction pattern of the as-synthesized sample shows formation of NiFe2O4 nanoparticles (NPs) as the main phase, with mean crystalline size ∼50 nm. While transmission electron microscopy (TEM) reveals nearly spherical morphology with mean particle diameter of 41 ± 5 nm, high-resolution TEM shows inter-planar distance (2.55 A) corresponding to the (1 1 3) plane of the spinel structure. Additionally, the Raman spectrum exhibits five Raman active modes (two A1g at 575 cm−1 and 710 cm−1; two Eg at 345 cm−1 and 670 cm−1; and one T2g at 497 cm−1) typical of NiFe2O4. X-band magnetic resonance (MR) data reveal a single broad resonance line in the whole temperature range (3.8 K ≤ T ≤ 300 K), with g-value decreasing monotonically from 3.10 ± 0.01 at 3.8 K to 2.77 ± 0.01 at 300 K. The temperature dependence of both resonance field and resonance linewidth show a remarkable change in the range of 60–70 K, herein credited to surface spin-glass behavior. The model picture used to explain the MR data assumes NPs with a core-shell structure. Below about 60–70 K the shell’s spin system progressively reveals a paramagnetic to spin-glass-like transition upon cooling, with a freezing temperature estimated at 2.1 ± 0.1 K. However, above about 60–70 K spins in the paramagnetic shell align along the NP’s core dipolar field, resulting in an effective enlarged nanoparticle size.

Reactivity of Ln(II) Complexes Supported by (C5H4Me)1– Ligands with THF and PhSiH3: Isolation of Ring-Opened, Bridging Alkoxyalkyl, Hydride, and Silyl Products

Reduction of CpMe3Ln(THF), 1-Ln (Ln = La and Gd; CpMe = C5H4Me), with KC8 in the presence of 2.2.2-cryptand (crypt) generates dark solutions, 2-Ln, with EPR spectra consistent with Ln(II) complexes: an eight-line hyperfine pattern for La at g = 1.971 and a broad single line for Gd at g = 1.988. The solutions decompose within minutes, and in the La system, a decomposition product was isolated in which a molecule of THF had been reduced by two electrons and ring-opened to generate an alkoxyalkyl-bridged bimetallic La(III) complex, [K(crypt)]2[(CpMe3La)2(μ-OCH2CH2CH2CH2)], 3-La. An analogous Pr complex, 3-Pr, was also crystallographically characterized. Since decomposition products were not readily isolated from the analogous yttrium CpMe3Y(THF)/KC8/crypt reaction, the composition of the solution of 2-Y was probed by addition of the hydrogen delivery reagent, PhSiH3, which had previously been reported to form U(III) hydrides from tris(cyclopentadienyl) U(II) complexes. This generated an Y(III) silyl complex,...

The characteristics of electron irradiated topaz: UV-Vis, EPR, and Mid-IR spectroscopic analyses

Electron irradiation was performed on topazes of two origin from Mogok valley of Mandalay, in Myanmar and Yen Bai province, in Vietnam. The samples were irradiated with 20 MeV electron beam (e-beam) to fluences of 1.34×1016 cm-2 and 2.65×1016 cm−2, respectively. Their characteristic spectra were investigated by UV–vis, EPR, FTIR and WD-XRF spectroscopy for comparison to natural state samples. Interaction between a radiation defect and impurity ions after irradiation resulted in sky blue topaz, which had the broad absorption band at 620 nm. The samples EPR lines, occurring a single broad isotropic line with g = 2.012, are correlated with an O- center interacting with two Al ions in the zigzag aluminum octahedral chains of the topaz structure. FTIR spectra indicated that the smoky or sky blue color may originated from the decomposition of hydroxyl group (OH) by the e-beam irradiation.

Magnetic characterization of mixed phases in FeVO4[sbnd]Co3V2O8 system

Dynamic and static magnetic properties of four nFeVO4/(1-n)Co3V2O8 composites obtained in reactions between nFeVO4 and (1-n)Co3V2O8 (n = 0.82, 0.80, 0.78 and 0.76) have been investigated by dc magnetometry and electron paramagnetic resonance (EPR). All samples were diphase containing both the howardevansite-type and the lyonsite-type phases in different proportions. Dc magnetic susceptibility study showed the Curie-Weiss paramagnetic behavior with strong antiferromagnetic (AFM) interaction in the high-temperature range and the phase transition to the AFM state at low temperatures. The calculated effective magnetic moment could be justified by the presence of high spin Fe3+ and Co2+ ions. The appearance of hysteresis loop in isothermal magnetisation at low temperature indicates the existence of the ferromagnetic component in all four samples, but only 0.5% of all magnetic ions are involved in this phase. EPR spectra recorded in high-temperature range (T > 90 K) consisted of a single broad line centred at ∼3.2 kG. The fitting of observed spectra with two Gaussian lineshape functions allowed to study the temperature dependence of EPR parameters (resonance field, linewidth, integrated intensity). This analysis suggests that EPR signal arises from two spin subsystems: paramagnetic Fe3+ ions subjected to AFM interaction and AFM spin pairs/clusters of iron/cobalt visible only at high temperatures. At low temperatures two transitions to AFM states, due to the mixture of two structural phases, are registered in magnetic susceptibility measurements.

Temperature dependent electron paramagnetic resonance study on magnetoelectric YCrO3

We report temperature dependent electron paramagnetic resonance (EPR) studies on polycrystalline YCrO3 samples at X-band (9.46 GHz) in the temperature range of 120 K–298 K. The EPR spectra exhibit a single broad line across the whole temperature range, attributed to Cr3+ ions. The variation of EPR spectra parameters (line width, integrated intensity, and g-factor) as a function of temperature was analyzed to understand the nature of spin-dynamics in the paramagnetic region of YCrO3. A peak in the g-factor suggests the presence of a new phase within the paramagnetic state at an intermediate point of temperature TIP ~ 230 K, attributed to the onset of short range canted antiferromagnetic correlations in the material much above 140 K, Néel temperature (TN) of YCrO3. The EPR intensity increases with a decrease in temperature up to TN due to the renormalization of the magnetic moments arising from the appearance of canted antiferromagnetic correlations. Further, temperature dependent dielectric measurements also exhibit an anomaly at ~230 K suggesting the presence of magnetodielectric coupling in YCrO3, with a possibility towards a relatively high temperature magnetodielectric system.

Investigation of Melts of Polybutylcarbosilane Dendrimers by 1H NMR Spectroscopy

Melts of polybutylcarbosilane (PBC) dendrimers from third (G3) up to sixth (G6) generations are investigated by 1H NMR spectroscopy in a wide temperature range up to 493 K. At room temperature, NMR spectra of G3-G5 dendrimers exhibit resolved, solution-like spectra (“liquid” phase). In contrast, the spectrum of the G6 dendrimer is characterized by a single unresolved broad line at whole temperature range, which supports the presence of an anomalous phase state of G6 at temperatures higher than glass transition temperature. For the first time, an unexpected transition of G5 dendrimer from a molecular liquid state to an anomalous state/phase upon temperature increase has been detected using NMR data. Specifically, an additional wide background line appears in the G5 spectrum above 473 K, and this line corresponds to a G5 state characterized by restricted molecular mobility, i.e., a state similar to the “anomalous” phase of G6 melt. The fraction of the G5 dendrimers in “anomalous” phase at 493 K is approximately 40%. Analysis of the spectral shapes suggests that changes in the G5 dendrimers are reversible with temperature.

EPR Studies for GdBa2Cu3 O 7−δ Added with Nanosized Ferrite ZnFe2 O 4 Before and After Irradiation by 3 MeV H + Ions

(ZnFe2O4)xGdBa2Cu3O7−δ superconducting samples, 0 ≤ x ≤ 0.40 wt%, were synthesized using a conventional solid-state reaction technique. The prepared samples were investigated using electron paramagnetic resonance (EPR) measurements. EPR measurements were carried out, at different temperatures 100 K ≤ T ≤ 300 K, for the prepared samples before and after irradiation by 3 MeV protons. An isotropic symmetric EPR line with g factor ≈2 is detected for the samples before irradiation, corresponding to Gd3+ ions. A single strong and broad isotropic EPR line is observed for all samples after irradiation with g ≈2.65. The broadness is attributed to the superposition of signals resulting from the clustering of Gd3+ ions and the dipole interaction between these ions. The number of spins (N) participating in EPR resonance showed a decrease with increasing temperature, while the activation energy (Ea) experienced an increase with x up to 0.06 wt% followed by a further decrease.

Electron paramagnetic resonance and low-field microwave absorption in the manganese–gallium oxide

Microwave absorption measurements in MnGa2O4 powders are carried out at X-band (8.8–9.8GHz) in 92–296K temperature range. For all temperatures, the electron paramagnetic resonance (EPR) spectra show a single broad line due to Mn2+ ions. Temperature dependence of the EPR parameters: the peak-to-peak linewidth (ΔHpp), the integrated intensity (IEPR) and the g-factor, suggests the presence of magnetic fluctuations that precede to antiferromagnetic ordering at low temperature. Additionally, the low-field microwave absorption (LFMA) is used to give further information on this material, giving also evidence of these magnetic fluctuations.

Electron paramagnetic resonance (EPR) study of free radicals in irradiated zinc poly methacrylate

Abstract We report the analysis of the X-band EPR spectrum of the free radical species formed in Zn(II) polymethacrylate (Zn(II) PMA), after degradation was induced in this polymer by 60 Co γ- radiation at room temperature. We begin by describing the synthesis and characterization of our samples and its polymerization before applying them several doses to induce degradation. Doses from 10 to 100 kGy in steps of 10 kGy were applied to the samples. At 10 kGy dose, the EPR spectrum shows the superimposed spectra of two species, namely: a typical pattern of an axially symmetrical singlet and a broad symmetric single line. The former can be attributed to peroxide radicals. After applying further doses, the EPR spectra of the samples display a series of superimposed lines on top of the mentioned axial singlet and the broad line. In these spectra, we recognize three sets of lines: a weak doublet, a quartet and quintet in addition to the already detected axially symmetrical line and the broad singlet. These can be assigned to scission radicals trapped in the polymeric matrix.

AlGaN Quantum Well Heterostructures for Mid-Ultraviolet Emitters with Improved Room Temperature Quantum Efficiency

We report on optical studies of exciton localization and recombination kinetics in two single 2.2 nm thick AlxGa1-xN/Alx+0.1Ga0.9-xN quantum well structures (x = 0.55 and 0.6) grown by plasma assisted molecular beam epitaxy on a c-sapphire substrate. Strong localization potential inherent for both the quantum well and barrier regions results in merging of the quantum well and barrier emission spectra into a single broad line centered at 285 nm (x = 0.55) and 275 nm (x = 0.6). Time-resolved photoluminescence measurements revealed surprising temperature stability of the photoluminescence decay time constant (approximate to 400 ps) relevant to the recombination of the quantum well localized excitons. This observation implies nearly constant quantum efficiency of the quantum well emission in the whole range from 4.6 to 300 K.