Emission Of Mg Research Articles

Regulation of optical, thermal, and electrical properties of GaNbO4 crystal by Mg2+ doping

In this paper, GaNbO4 crystal properties were regulated by Mg2+ doping. The refractive indexes, optical properties, and thermal properties were characterized, the influence of Mg2+ doping and air annealing on the conductivity and photoluminescence properties of GaNbO4 was systematically studied. The Mg2+ doping causes the ultraviolet absorption edge of GaNbO4 crystal blue shift, and the band gap of Mg: GaNbO4 crystal is 3.463 eV. The thermal expansion coefficient in b-direction was presented, which is -0.977 × 10−6 K−1; the high-temperature resistivity of the Mg: GaNbO4 crystal decreases from 1.7 × 109 to 3.0 × 106 W·cm in the temperature range of 500 to 800 °C, decreasing by about an order of magnitude after air annealing. The photoluminescence spectrum shows an enhanced blue emission in Mg: GaNbO4 crystals, and x-ray photoelectron spectroscopy was measured, the element's chemical states and oxygen vacancies in the crystal were analyzed. The regulation mechanism of the crystal properties was discussed in detail.

Low-carbon operation method of microgrid considering carbon emission quota trading

With the proposal of carbon peaking and carbon neutrality goals, distributed energy is developing rapidly, and microgrid is widely proposed and utilized to realize flexible and efficient application of distributed energy and improve its local consumption. But with the problem of large amounts of carbon emissions generated by the microgrid arises, it is significant to stimulate the carbon reduction potential of microgrids. This paper proposes a low-carbon operation method of microgrid considering carbon emission quota trading, where energy-carbon coupling units, i.e., distributed generator (DG) and industrial loads, are considered, and based on which microgrid utility model considering carbon emission quota trading is constructed. Simulation results shows adding carbon emission quota trading with energy trading can not only obtain higher revenue of MG, but also achieve the purpose of guiding MG to actively participate in carbon emission reduction actions, and reduce the carbon emission of MG.

Simultaneous J-, H-, K- and L-band spectroscopic observations of galactic Be stars

Context. It is already accepted that Be stars are surrounded by circumstellar envelopes, which are mostly compatible with a disc geometry in Keplerian rotation. Their infrared region is characterised by a moderate flux excess and the presence of hydrogen recombination lines that allow us to obtain information on the physical and dynamical structure of different regions inside the disc. Nevertheless, many of the infrared studies available in the literature show low-resolution spectra, or are restricted to a small object sample or describe just an individual object. Some others analyse reduced spectral ranges or just one infrared band. Aims. We aim to obtain a more complete characterisation of the properties of the circumstellar environment of Be stars that helps to constrain the theoretical models of the Be phenomenon. Methods. Throughout the last decade, we used the spectroscopic facilities at the Gemini and Las Campanas observatories to obtain quasi-simultaneous spectra in the J, H, K, and L bands of a sample of Be stars with medium resolution. Results. We present near-infrared, medium-resolution spectra of a sample of galactic Be stars with different spectral subtypes and luminosity classes. We measure different parameters of the hydrogen recombination lines from the Paschen, Brackett, Pfund, and Humphreys series, and use them to diagnose physical conditions in the circumstellar environment. We analysed the equivalent-width (EW) ratio between Brα and Brγ lines and different diagrams of flux ratios. We also identify lines from He i, C i, N i, O i, Na i, Mg i, Mg ii, Si i, Fe i, and Fe ii. Analysing the EW measurements of particular He i, Mg ii, Fe i, Fe ii and O i lines, we find that for some lines they correlate with the spectral type of the star. Particularly, the emission of the O i λ 1.3168 μm line decreases towards the later spectral types. Conclusions. We present an atlas of 22 Be stars, that covers a wide infrared (IR) spectral range with quasi-simultaneous observations. From a detailed analysis, we define new complementary criteria to Mennickent’s classification of Be stars according to their disc opacity. Some objects in our sample present compact thick envelopes, while in others the envelope is extended and optically thin. The correlation between the full widths at half maximum and the peak separation (ΔV) versus V sin i for the Br10, Brδ, and Hu14 lines reveals that the broadening mechanism is rotational. The Lyβ fluorescence is a key mechanism to explain the intensity of the emission of Mg ii and O i lines.

An Exquisitely Deep View of Quenching Galaxies through the Gravitational Lens: Stellar Population, Morphology, and Ionized Gas

Abstract This work presents an in-depth analysis of four gravitationally lensed red galaxies at z = 1.6–3.2. The sources are magnified by factors of 2.7–30 by foreground clusters, enabling spectral and morphological measurements that are otherwise challenging. Our sample extends below the characteristic mass of the stellar mass function and is thus more representative of the quiescent galaxy population at z > 1 than previous spectroscopic studies. We analyze deep VLT/X-SHOOTER spectra and multiband Hubble Space Telescope photometry that cover the rest-frame UV-to-optical regime. The entire sample resembles stellar disks as inferred from lensing-reconstructed images. Through stellar population synthesis analysis, we infer that the targets are young (median age = 0.1–1.2 Gyr) and formed 80% of their stellar masses within 0.07–0.47 Gyr. Mg ii λλ 2796, 2803 absorption is detected across the sample. Blueshifted absorption and/or redshifted emission of Mg ii are found in the two youngest sources, indicative of a galactic-scale outflow of warm (T ∼ 104 K) gas. The [O iii] λ5007 luminosity is higher for the two young sources (median age less than 0.4 Gyr) than the two older ones, perhaps suggesting a decline in nuclear activity as quenching proceeds. Despite high-velocity (v ≈ 1500 km s−1) galactic-scale outflows seen in the most recently quenched galaxies, warm gas is still present to some extent long after quenching. Altogether, our results indicate that star formation quenching at high redshift must have been a rapid process (<1 Gyr) that does not synchronize with bulge formation or complete gas removal. Substantial bulge growth is required if they are to evolve into the metal-rich cores of present-day slow rotators.

Temporal characterization of fundamental plasma parameters in pulsed liquid electrode plasma (LEP) optical emission spectrometry

The fundamental characteristics of liquid electrode plasma (LEP), a pulsed plasma source for optical emission spectrometry, were investigated. Two distinct phases were observed during the process of pulsed plasma generation, namely bubble generation and active plasma discharge. The ionization efficiency of the LEP, with Mg as a representative analyte, was gauged from the ratio of Mg II 279.553 nm to Mg I 285.213 nm emission and was found to increase from about 5% to 20% in a close-to-linear fashion with the discharge voltage from 800 V to 1200 V. The Mg II/Mg I ratio of the LEP was 2.5 to 3 orders of magnitude less than that typically offered by an inductively coupled plasma (ICP) but was comparable to other solution-based glow discharges. It was found that an off-time interval of more than 150 ms between successive discharge pulses was required to obtain a stable pulse-to-pulse discharge current. Temporally resolved emissions of Mg II 279.6 nm, Mg I 285.2 nm, Fe I 373.5 nm, OH band head at 306 nm, and Hα line at 656.3 nm showed that the background species (OH band and Hα line) reached their maximum emission intensities at around 0.5 ms to 0.7 ms with respect to the onset of the discharge pulse whereas the maximum emissions were observed between 0.7 ms to 0.9 ms for analyte species (Mg and Fe lines). The electron density observed in the present work was in the range from 5.7 × 1015 cm−3 to 8.2 × 1015 cm−3, which was similar to those found in an analytical ICP. The temporal averaged OH rotational temperature was 3300 K, which was comparable to the values of an analytical ICP and solution-based glow discharges. By contrast, the temporally averaged Fe I excitation temperature was around 8900 K, which was even higher than that of an analytical ICP and roughly triple the values obtained by techniques based on glow discharge of liquid samples.

Effect of Mg doping on the improvement of photoluminescence and magnetic properties of NiO nanoparticles

NiO nanoparticles doped with different concentration of Mg were synthesized by a low cost wet chemical method. XRD characterization indicated that the fcc structure of NiO is not affected with Mg doping. TEM analysis further reveals the Mg doping induced reduction in grain agglomeration along with the spherical shape transformation in NiO. Significant enhancement of UV emission in Mg doped NiO nanoparticles is evident from photoluminescence characterization. Magnetic characterization of the samples showed that all the samples show weak ferromagnetism along with the dominance of background antiferromagnetism at room temperature. The perseverance of background antiferromagnetic order is further probed through Raman characterization. All the samples show first order antiferromagnetic to weak ferromagnetic transition along with the presence of shape memory effect as evident by the negative slope in Arrott plot. The Ni0.9Mg0.1O sample with much enhanced UV emission and magnetization could find the usefulness in UV optoelectronic device, spintronic device etc.

Light emission induced by electric current at room temperature through the defect networks of MgO nanocubes

Magnesium oxide (MgO) is generally a wide band-gap oxide unable to conduct electric current in the bulk at room temperature. In this study, MgO nanocubes synthesized by self-burning micro-sized Mg metal powders in air showed electrical conductivity when they were sandwiched between two gold-mesh electrodes and steadily applied a voltage at room temperature (∼25 °C). In addition, a simultaneous light emission caused by the microdischarge of nitrogen molecules occurred adjacent to the cathode. The light emission was observed when traces of water vapor existed in the gas environment. In the case of a voltage pulse produced by switching off, transient emissions of Mg I and Mg II were detected on both sides of the electrodes. However, those steady and transient light emissions were not observed in the commercial MgO nanoparticles devoid of nanocubes. The light emissions shown in the cases of the steady-state might be caused by electron injection into the empty conductive states, which exist along the edges of MgO nanocubes, as a result of the spontaneous dissociation of water vapors at reactive sites of the nanocube surfaces as well as a result of the reduction of the energy barriers between the cathode and MgO nanocubes in contact. For transient emission, electrons trapped in the low coordinate sites were released with voltage pulse and neutralized the nearby Mg+ and Mg2+ ions, driving them into the excited neutral states, Mg I and Mg II.

Quiet-Sun and Coronal Hole in Mg II k Line as Observed by IRIS

Abstract Coronal hole (CH) regions are dark in comparison to the quiet Sun (QS) at coronal temperatures. However, at chromospheric and transition region temperatures, the QS and CHs are hardly distinguishable. In this study, we have used the Mg ii 2796.35 Å spectral line recorded by the Interface Region Imaging Spectrometer (IRIS) to understand the similarities and differences in the QS and CH at chromospheric levels. Our analysis reveals that the emission from Mg ii k3 and k2v that originates in the chromosphere is significantly lower in CH than in QS for the regions with similar magnetic field strength. The wing emissions of Mg ii k that originates from the photospheric layer, however, do not show any difference between QS and CH. The difference in Mg ii k3 intensities between QS and CH increases with increasing magnetic field strength. We further studied the effects of spectral resolution on these differences and found that the difference in the intensities decreases with decreasing spectral resolution. For a resolution of 11 Å, the difference completely disappears. These findings are not only important for mass and energy supply from the chromosphere to the corona but also provides essential ingredients for the modeling of the solar spectral irradiance for the understanding of the Sun–climate relationships.

A novel rare-earth free red long-persistent phosphor: Mg2GeO4:Mn4+

Abstract Red-emitting long-persistent phosphor Mg 2 GeO 4 : Mn 4+ was prepared by a high-temperature solid-state reaction. The photoluminescence and afterglow properties of Mg 2 GeO 4 : xMn 4+ phosphors were studied systematically. Furthermore, to improve the afterglow performance, co-doped Re 3+ (Re = Pr, Er, Nd and Yb) ions into Mg 2 GeO 4 : 0.001Mn 4+ separately to adjust the trap depth or increase the trap density was performed. The duration of Mg 2 GeO 4 : 0.001Mn 4+ can be observed 30 min by naked eyes, and the initial brightness and afterglow duration are significantly improved after Re 3+ ions are doped respectively. Especially, the afterglow emission of Mg 2 GeO 4 : Mn 4+ , Yb 3+ can last for 2 h. This investigation shows up a rare Mn 4+ -doped long-afterglow phenomenon, and provides a new and efficient red afterglow material for potential application.

On the ultraviolet anomalies of the WASP-12 and HD 189733 systems: Trojan satellites as a plasma source

We suggest an additional possible plasma source to explain part of the phenomena observed for the transiting hot Jupiters WASP-12b and HD 189733b in their ultraviolet (UV) light curves. In the proposed scenario, material outgasses from the molten surface of Trojan satellites on tadpole orbits near the Lagrange points L$_4$ and L$_5$. We show that the temperature at the orbital location of WASP-12b is high enough to melt the surface of rocky bodies and to form shallow lava oceans on them. In case of WASP-12b, this leads to the release of elements such as Mg and Ca, which are expected to surround the system. The predicted Mg and Ca outgassing rates from two Io-sized WASP-12b Trojans are $\approx 2.2 \times 10^{27}$ s$^{-1}$ and $\approx 2.2 \times 10^{26}$ s$^{-1}$, respectively. Trojan outgassing can lead to the apparent lack of emission in Mg{\sc ii}\,h\&k and Ca{\sc ii}\,H\&K line cores of WASP-12. For HD 189733b, the mechanism is only marginally possible due to the lower temperature. This may be one of the reasons that couldn't explain the early ingress of HD 189733b observed in the far-UV (FUV) C{\sc ii} doublet due to absence of carbon within elements outgassed by molten lava. We investigate the long-term stability region of WASP-12b and HD 189733b in case of planar and inclined motion of these satellites and show that unlike the classical exomoons orbiting the planet, Io-sized Trojans can be stable for the whole systems life time.

Defect based violet–blue emission of Mg doped ZnO annealed at different temperatures

This paper describes structural and optical characterization of Mg doped ZnO nanoparticles. The system Zn1−xMgxO with x = 0.0, 0.01, 0.03, 0.05, 0.1 were prepared by a simple chemical method and annealing at different temperatures, T = 500, 700 and 900 °C. XRD spectra and the Rietveld refinement show that the crystalline phase of these samples belongs to the wurtzite hexagonal structure of space group P63mc. The PL results show three main emission bands in the violet and blue emission regions. The presence of several emission bands are attributed to free excitation transitions, interstitial Zn, local zinc vacancy, single ionized oxygen vacancy, and deep level emissions. PL studies at 500 °C revealed that visible PL emission was enhanced with doping concentration (x). Mg doped ZnO structures have changed the optical properties significantly.

Direct ultraviolet imaging and spectroscopy of betelgeuse

Direct images of Betelgeuse were obtained over a span of 4 years with the Faint Object Camera on the Hubble Space Telescope. These images reveal the extended ultraviolet continuum emission (about 2 times the optical diameter), the varying overall ultraviolet flux levels and a pattern of bright surface continuum features that change in position and appearance over several months or less. Concurrent photometry and radial velocity measures support the model of a pulsating star, first discovered in the ultraviolet from IUE. Spatially resolved HST spectroscopy reveals a larger extention in chromospheric emissions of Mg II as well as the rotation of the supergiant. Changing localized subsonic flows occur in the low chromosphere that can cover a substantial fraction of the stellar disk and may initiate the mass outflow.

Electrical and Optical Characterization of Mg Doping in GaN

Apossible evidence of Mg related emission in Mg doped GaN material is observed inoptical measurement, even without thermal annealing. Meanwhile, the electrical properties of the sample improve when Ni/Au contact layer was annealed up to 400°C, but degrade at further temperature. We propose that such behavior isrelated to degradation of surface morphology of metal contact at higher temperature.

Plasma property effects on spectral line broadening in double-pulse laser-induced breakdown spectroscopy

Double-pulse Laser-Induced Breakdown Spectroscopy (LIBS) in an orthogonal configuration was used to investigate plasma temperature and electron density effects on Mg II emission spectral line broadening. The experiments were carried out with two Nd:YAG lasers, one operating at 355 nm for ablation and the other one at 1064 nm for plasma reheating in air at atmospheric pressure. Temporally resolved plasma temperature and electron density were measured at various delay times. Data in this study show prolonged emission of Mg II (280.27 nm) as well as enhancement of the signal intensity when using double-pulse excitation compared to the single-pulse case. An enhancement of ∼8× was attained with a delay between the laser pulses equal to 1 μs. The enhancement was accompanied by higher plasma temperature and increased electron density. The double-pulse LIBS configuration provides energy to sustain the plasma emission at a period in time when the linewidth is minimum, thereby improving the analytical capabilities of low spectral resolution instrumentation typically used in LIBS system.

The Research on Infrared and Luminescent Spectra of a New Mg (II) Luminescent Materials

In order to prepare the highlight luminescent material, we synthesized a highlight blue luminescent material, salicylaldehyde-4, 4’-diaminodiphenylsulfone Mg (II), by the reaction of Magnesium chloride hexahydrate with salicylaldehyde-4, 4’-diaminodiphenylsulfone. The results indicate that the maximum fluorescence emissions of Mg (II) complex material are at 459 nm (in solid), 466 nm (in DMSO), 476 nm (in CH3OH) and 464 nm (in CH3CH2OH), respectively. The Mg (II) material exhibits the strongest fluorescence in solid than that in DMSO, CH3OH and CH3CH2OH solution.

Mg doping reduced full width at half maximum of the near-band-edge emission in Mg doped ZnO films

Sol–gol method was employed to synthesize Mg doped ZnO films on Si substrates. The annealing temperature-dependent structure and optical property of the produced samples were studied. An interesting result observed is that increasing Mg concentration in the studied samples induces the full width at half maximum (FWHM) of their near-band-edge (NBE) emission decrease and the defect related emission of the corresponding sample suppresses drastically. The possible mechanism of the observed result is discussed.

Explanation of the activity sensitivity of Mn I 5394.7 Å

There is a long-standing controversy concerning the reason why the Mn I 5394.7 A line in the solar irradiance spectrum brightens more at larger activity than most other photospheric lines. The claim that this activity sensitivity is caused by spectral interlocking to chromospheric emission in Mg II h & k is disputed. Classical one-dimensional modeling is used for demonstration; modern three-dimensional MHD simulation for verification and analysis. The Mn I 5394.7 A line thanks its unusual sensitivity to solar activity to its hyperfine structure. This overrides the thermal and granular Doppler smearing through which the other, narrower, photospheric lines lose such sensitivity. We take the nearby Fe I 5395.2 A line as example of the latter and analyze the formation of both lines in detail to demonstrate and explain granular Doppler brightening. We show that this affects all narrow lines. Neither the chromosphere nor Mg II h & k play a role, nor is it correct to describe the activity sensitivity of Mn I 5394.7 A through plage models with outward increasing temperature contrast. The Mn I 5394.7 A line represents a proxy diagnostic of strong-field magnetic concentrations in the deep solar photosphere comparable to the G band and the blue wing of H-alpha, but not a better one than these. The Mn I lines are more promising as diagnostic of weak fields in high-resolution Stokes polarimetry.

The influence of ambient conditions on properties of Mg xZn 1−xO films by sputtering

The Mg x Zn 1− x O films were prepared in different Ar–O 2 mixture ambience by magnetron sputtering. According to the X-ray diffraction (XRD) patterns and the energy dispersive X-ray spectroscopy (EDS) results, it was found that the Mg contents in the films varied with the different ratios of O 2/O 2+Ar, and the crystal quality of the films improved with the increasing of Mg contents. Meanwhile, the ultraviolet and visible (UV–vis) absorption spectroscopy indicated that the band gap of the films also increased. Moreover, it could be seen that the photoluminescence (PL) spectrum was different from that of undoped Zinc oxide (ZnO) films or the results in other reports on the Mg x Zn 1− x O films: there was no blueshift effect happening for the near-band-edge (NBE) emission in Mg x Zn 1− x O films with different Mg contents.

Blueshift of near band edge emission in Mg doped ZnO thin films and aging

Pure and Mg doped ZnO thin films were deposited at 400 °C on glass substrates by pulsed laser deposition. An x-ray diffractometer (XRD) was used to investigate the structural properties of the thin films. It is found that all the thin films have a preferred (002) orientation. The peak position of (002) orientation is found to shift from 34.39° to 34.55°. The lattice constants of ZnO thin films were also obtained from XRD data. It is found that, with the increase of the dopant concentration, the lattice constant a decreases from 3.25 to 3.23 Å, and c decreases from 5.20 to 5.16 Å. From the spectrophotometer transmittance data, the band gap energies of the thin films were calculated by a linear fitting process. The band gap energy of Mg doped ZnO thin film increases with increasing dopant concentration. In photoluminescence (PL) spectra, two PL emission peaks are found in pure ZnO thin films, one is the near band edge (NBE) emission at 3.28 eV, and the other is green-yellow-red emission at around 2.4 eV. However, with the increase of the dopants, no green-yellow-red emissions are found in PL of Mg doped ZnO thin films. The NBE emission has a blueshift compared with that of pure ZnO thin film (as much as 0.12 eV). As time goes on, NBE emission in pure ZnO thin film is enhanced, and the green-yellow-red emissions disappear.

Room temperature UV emission of Mg xZn 1− xO films

II–VI wide band-gap semiconductor ternary Mg x Zn 1− x O nanocrystalline films have been successfully formed on conductive glass from ZnO powder by electrophoresis deposition (EDP). In comparison with ZnO powder, the Mg x Zn 1− x O films presented a more preferential crystalline orientation. Room temperature (RT) PL spectra of Mg x Zn 1− x O films revealed a stronger band-edge ultraviolet (UV) emission and a narrower FWMH of 13 nm than that of ZnO powder. The UV emission peak of Mg x Zn 1− x O film is located at the range of 375–381 nm with a small blue shift from that of ZnO powder. In addition, the ratio of PL peak intensity of band-edge emission to the deep-level emission in Mg x Zn 1− x O films reached as high as 135:1 while compared with 23:1 of ZnO powder under the same He–Cd laser excitation level. Consequently, these electrophoretic deposition (EPD) Mg x Zn 1− x O films exhibited a good quality for excitonic emission at RT.