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Characterizing HR?3549?B using SPHERE
摘要： Aims. In this work, we characterize the low-mass companion of the A0 field star HR 3549. Methods. We observed HR 3549B in imaging mode with the near-infrared branch (IFS and IRDIS) of SPHERE at the VLT, with IFS in Y J mode and IRDIS in the H band. We also acquired a medium-resolution spectrum with the IRDIS long-slit spectroscopy mode. The data were reduced using the dedicated SPHERE GTO pipeline, which is custom-designed for this instrument. We employed algorithms such as PCA and TLOCI to reduce the speckle noise. Results. The companion was clearly visible with both IRDIS and IFS. We obtained photometry in four different bands and also the astrometric position for the companion. Based on our astrometry, we confirm that it is a bound object and set constraints on its orbit. Although several uncertainties still remain, we estimate an age of ～100–150 Myr for this system, yielding a most probable mass for the companion of 40–50 MJup and Teff ～ 2300?2400 K. Compared with template spectra, this points to a spectral type between M9 and L0 for the companion, commensurate with its position on the color–magnitude diagram.
关键词： techniques: imaging spectroscopy,planetary systems,methods: data analysis,instrumentation: spectrographs
更新于2025-09-04 15:30:14
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Two distinct surface terminations of SrVO <sub/>3</sub> (001) ultrathin films as an influential factor on metallicity
摘要： Pulsed laser deposition-grown SrVO3 (001) ultrathin films on SrTiO3 (001) substrates were investigated by in situ low-temperature scanning tunneling microscopy and spectroscopy. SrVO3 (001) ultrathin films showed two distinct surface terminations. One termination was a ((√2 × √2)-R45° reconstruction as was previously observed for SrVO3 (001) thick films, while the other was a ((√5 × √5)-R26.6° reconstruction. Scanning tunneling spectroscopy revealed that the ((√2 × √2)-R45° surface shows a metallic electronic structure, whereas the ((√5 × √5)-R26.6° surface exhibits a significantly reduced density of states at the Fermi level. These results suggest that the surface reconstruction may be an important factor to influence metallicity in epitaxial ultrathin films of transition metal oxides.
关键词： ultrathin films,scanning tunneling microscopy,scanning tunneling spectroscopy,SrVO3,metallicity,surface terminations
更新于2025-09-04 15:30:14
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Integrated spectral and spatial information extraction in Raman spectroscopy
摘要： Raman spectroscopy has been widely used to analyze various substances quantitatively. Conventional studies are primarily focused on the spectral characteristics of Raman scattering. The spatial distribution is always ignored, which can be used to observe the physical properties, such as the particle size. In this article, the spatial information has been extracted from the Raman spectra of barium nitrate, demonstrating that the evident spatial width broadening varied with the particle size. The numerical result shows that the spatial width has a better linear correlation with the particle size, while the Raman intensity has a poor linear correlation. The integrated spectral and spatial information extracted in Raman spectroscopy has a potential application in the quantitative analysis of physical properties.
关键词： spatial distribution,Raman spectroscopy,Particle size
更新于2025-09-04 15:30:14
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High resolution spectropolarimetry: from Astrophysics to ECR plasmas
摘要： Electron Cyclotron Resonance (ECR) plasmas with high density and high temperature are required by the injectors for the Accelerators and by interdisciplinary studies in Astrophysics and Nuclear Astrophysics. Understanding and further developing magnetic traps requires accurate measurements of the physical properties of the con?ned plasma, such as density, temperature and ionization state, not allowed by the commonly used diagnostic methods (imaging, low resolution spectroscopy). Here, we show the potentiality of a few diagnostic applications of high resolution spectroscopy in the visible range, routinely used in Astrophysics to measure stellar physical parameters such as e?ective temperature, surface gravity, chemical abundances. In addition, we show that polarimetry is a powerful technique to derive the morphology of stellar magnetic ?elds, whose knowledge is necessary for a correct interpretation of spectra from magnetized plasmas. An application of these non-invasive methods to B-min ECR plasma concerning optical emission is discussed in view of a better understanding of the plasma structure, magnetic con?nement properties and heating processes.
关键词： Plasma diagnostics - charged-particle spectroscopy,Polarisation,Ion sources (positive ions, negative ions, electron cyclotron resonance (ECR), electron beam (EBIS))
更新于2025-09-04 15:30:14
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Preliminary results of optical emission spectroscopy by line ratio method in the RF negative ion source at ASIPP
摘要： Optical emission spectroscopy (OES) using the trace rare gases of Ar and Xe have been carried out in a radio frequency (RF) driven negative ion source at Institute of Plasma Physics, Chinese Academy of Science (ASIPP), in order to determine the electron temperature and density of the hydrogen plasma. The line-ratio methods based on population models are applied to describe the radiation process of the excited state particles and establish their relations with the plasma parameters. The spectral lines from the argon and xenon excited state atoms with the wavelength of 750.4 nm and 828.0 nm are used to calculate the electron temperature based on the corona model. The argon ions emission lines with the wavelength of 480 nm and 488 nm are selected to calculate the electron density based on the collisional radiative model. OES has given the preliminary results of the electron temperature and density by varying the discharge gas pressure and RF power. According to the experimental results, the typical plasma parameters is Te≈2?4 eV and ne≈1×1017?8×1017 m-3 in front of plasma grid.
关键词： RF negative ion source,optical emission spectroscopy,neutral beam injection
更新于2025-09-04 15:30:14
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Near-Field and Far-Field Thermal Emission of an Individual Patch Nanoantenna
摘要： The far-field spectral and near-field spatial responses of an individual metal-insulator-metal nanoantenna are reported, using thermal fluctuations as an internal source of the electromagnetic field. The far-field spectra, obtained by combining Fourier transform infrared spectroscopy with spatial modulation based on a light falloff effect in a confocal geometry, have revealed two distinct emission peaks attributed to the excitation of the fundamental mode of the nanoantenna at two distinct wavelengths. Superresolved near-field images of the thermally excited mode have been obtained by thermal radiation scanning tunneling microscopy. Experimental results are supported by numerical simulations showing that it is possible to excite the same mode at different wavelengths near a resonance of the insulating dielectric material forming the antenna.
关键词： near-field,nanoantenna,thermal emission,microscopy,spectroscopy,far-field
更新于2025-09-04 15:30:14
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IR and XAFS studies of photoluminescent Ag-type zeolite-A
摘要： We examined the relation between the zeolite framework, Ag clusters, and properties of photoluminescence (PL) using in-situ infrared spectroscopy (IR) and X-ray absorption fine structure (XAFS). The Ag clusters are generated in the cavity of Ag-type zeolite-A that is cooled to room temperature after heating at 500°C for 24 hour under vacuum or in atmosphere. The Ag clusters in the zeolite cavity break down when air is introduced. According to the formation and breakdown of the Ag cluster, the infrared spectrum of the zeolite framework changed slightly. Then, this change was compensated by irradiation of the excitation light. Results suggest that the structural change in the zeolite induced by the formation and breakdown of the Ag clusters is a key point of the PL mechanism.
关键词： infrared spectroscopy,XAFS,Ag clusters,photoluminescence,Ag-type zeolite-A
更新于2025-09-04 15:30:14
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Hyperspectral Retrieval of Canopy Water Content Through Inversion of the Beer-Lambert Law
摘要： The retrieval of quantitative equivalent water thickness on canopy level (EWTc) is an agriculturally important task for hyperspectral remote sensing. In this study the Beer-Lambert law is applied to inversely determine water content from measured winter wheat spectra collected in 2015 and 2017. The spectral model is calibrated using a look-up-table (LUT) of 50.000 PROSPECT spectra. Validation was performed using two leaf optical properties datasets (LOPEX93 and ANGERS) and in-situ data acquired in Southern Germany. After considering destructive in-situ water content measurements separately for leaves, stems, and fruits, results indicate optically active plant water by plant component in the 930 to 1060 nm range of canopy reflectance. Results for spectrally derived EWTc were most promising for leaves and ears reaching coefficients of determination up to 0.75 and a normalized RMSE (nRMSE) of 24% between measured and estimated canopy water content.
关键词： EnMAP,hyperspectral,agriculture,canopy water content,spectroscopy
更新于2025-09-04 15:30:14
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Recent Advances and Applications of Near Infrared Spectroscopy for Honey Quality Assessment
摘要： Currently, most of the technologies used to identify honey quality are inefficient and costly. There is a necessity to develop a more effective one for honey quality assessment. Near Infrared Spectroscopy (NIRS) has the potential to be such a technique for its unique characteristics. This study reviews recent advances and applications of NIR spectroscopy in honey authentication domain including constituents, adulteration, brand, botanical origin and geographical origin. It presents a comprehensive using of this technology, with advantages and limitations, in honey quality detection, which offers insights on selecting the most appropriate NIR spectroscopic method for samples presentation, spectral acquisition, spectral pretreatment and modeling. Future research is to be focused on increasing model robustness, developing overall NIR spectroscopic database and a NIR-based integrated technology system on honey quality assessment.
关键词： honey,near infrared spectroscopy,Advances,detection,applications
更新于2025-09-04 15:30:14
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Research on Beam Emission Spectroscopy Combined HL-2A Tokamak Real Experimental Data With Spectra Simulation Code
摘要： A beam emission spectroscopy (BES) diagnostic system has been developed on HL-2A tokomak. Combined with motional Stark effect (MSE) diagnostics, the BES could assess the radial electric ?eld Er and the safety factor q, which play an important role in plasma control and impurity transport processes. A simulation of spectra (SOS) code has been developed for spectra simulations based on various tokamak devices’ real situations. It can be used for designing visible spectral diagnostics systems and predicting their performance. In this paper, based on the HL-2A real experimental running parameters, we used the SOS code to simulate BES and MSE spectra. These spectra were consistent with experimental data ?tting results. The SOS code was also able to get the safety factor q and other parameters. The results reveal that the SOS code could be used to design similar diagnostic systems for ITER in the future.
关键词： neutral beam injection (NBI) diagnostics,motional Stark effect (MSE),simulation of spectra (SOS),Beam emission spectroscopy (BES)
更新于2025-09-04 15:30:14