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- 摘要
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<i>l</i> -Stercobilin-HCl and <i>d</i> -Urobilin-HCl. Analysis of Their Chiroptical and Conformational Properties by VCD, ECD, CPL Experiments and MD, DFT Calculations
摘要： Vibrational circular dichroism (VCD) and IR spectra of dichloromethane solutions of l-stercobilin and d-urobilin hydrochlorides have been recorded in the mid-IR region. The spectra are best interpreted by combining molecular dynamics (MD) calculations and DFT calculations within the QM/MM ONIOM-type framework, and the combined predicted results are better and more informative than the more standard analysis provided by DFT calculations. The same approach also sheds light on the Cotton effect sign inversion of room temperature versus low temperature electronic CD (ECD) spectra of the same compounds in methanol-glycerol solution. Finally, circularly polarized luminescence (CPL) spectra for l-stercobilin in chloroform solution provide information on the excited state geometry of this molecule.
关键词： Vibrational circular dichroism,electronic CD,molecular dynamics,IR spectra,QM/MM ONIOM-type framework,Cotton effect,circularly polarized luminescence,DFT calculations
更新于2025-09-23 15:21:21
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Field dependence of THz spectra of effective models for <i>α</i> -RuCl <sub/>3</sub>
摘要： We calculate polarized terahertz (THz) spectra of two effective models for a honeycomb-lattice magnet α-RuCl3 by using a numerical exact-diagonalization method. One of the two models is the ab initio model proposed in H.-S. Kim and H.-Y. Kee [Phys. Rev. B 93, 155143 (2016)] and the other is the large-|K| model that we have proposed by an empirical way in order to explain experimental results for α-RuCl3. We discuss the magnetic-?eld dependence of the lowest-excitation mode in the polarized THz spectra for the two models. We ?nd that the energy gap of the lowest-excitation mode in both models does not close and increases almost linearly above the critical ?eld, where the zigzag order is suppressed. From the obtained results, we point out that the low-energy excitation is mainly governed not by the Kitaev interaction but by the Heisenberg interaction and the off-diagonal interactions.
关键词： exact-diagonalization method,honeycomb-lattice magnet,α-RuCl3,THz spectra,Heisenberg interaction,Kitaev interaction
更新于2025-09-23 15:21:21
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Measurement of Directional Spectral Emissivity at High Temperatures
摘要： Emissivity is a signi?cant parameter to describe the thermal radiation characteristics of the objects. It has important applications in thermal control of spacecrafts, highly ef?cient use of solar energy, buildings’ energy insulation and saving, and so on. Besides, more attention is attached to selective control of thermal emission by using micro-/nanostructures. In this work, to measure directional spectral emissivity, a measurement facility is developed which includes a sample heater with temperature control, a blackbody source, mirror assembly and a Fourier transform infrared spectrometer with different detectors. A sample heater is designed, and by using ceramic electric heaters, samples can be heated up to 1400 K at a high heating speed. And a new kind of water-cooled surface of the sample heating unit is designed to reduce the error by reducing the thermal radiation from surface of the heating unit so that measurement accuracy is improved. An electro-controlling rotating stage is adopted, and measuring angle is up to 60°. A SiC wafer is used as the reference to test the directional spectral emissivity measurement facility, and uncertainty is estimated.
关键词： High temperatures,Measurement,Directional emissivity,Spectra
更新于2025-09-23 15:21:21
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Diamond nanofeathers
摘要： This paper reports a special diamond nanostructure which we call diamond nanofeathers (DNFs). The nanostructure was discovered after electrochemically etching doped nanocrystalline diamond (NCD) films. With high resolution SEM, we have repeatedly observed highly porous, fractal-like geometry with “shafts”, “barbs” and “barbules” of the DNFs. A DNF has very high aspect ratio, with a height comparable to the thickness of the etched diamond film and a lateral size as small as several nanometers. This diamond nanostructure seems not to belong to either conventionally defined NCD or ultrananocrystalline diamond (UNCD). The Raman spectra tell that after the electrochemical etch, the DNFs have lower signals from the grain boundaries, compared with the Raman spectra before the etch, which suggests the pores of the DNFs was related with mass loss from the grain boundaries. Preliminary electrochemical characterization has observed more than 300× capacitance increase after the DNFs are fabricated out of a NCD film. With the specific pore size and the ease of fabrication, the DNFs could be a great material choice for supercapacitors, batteries, sensors, and solar cells etc.
关键词： Diamond nanofeathers,Supercapacitors,Nanocrystalline diamond,Raman spectra,Electrochemical etching
更新于2025-09-23 15:21:21
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4-{(Z)-[4-(Diethylamino)phenyldiazenyl]}phthalonitirle and Phthalocyanines Thereof
摘要： 4{(Z)-[4-(Diethylamino)phenyldiazenyl]}phthalonitrile was synthesized by diazotization and azo coupling and used to prepare tetrakis-4-(4-{(Z)-[4-(diethylamino)phenyl]diazenyl})phthalocyanine and its cobalt, nickel, zinc and magnesium complexes by template synthesis. The spectral properties of the synthesized compounds were studied.
关键词： azo chromophore,4-aminophthalonitrile,electronic absorption spectra,metal phthalocyanines
更新于2025-09-23 15:21:21
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Disentangling Coupling Effects in the Infrared Spectra of Liquid Water
摘要： A quantitative characterization of intermolecular and intramolecular couplings that modulate the OH-stretch vibrational band in liquid water has so far remained elusive. Here, we take up this challenge by combining the centroid molecular dynamics (CMD) formalism, which accounts for nuclear quantum effects, with the MB-pol potential energy function, which accurately reproduces the properties of water across all phases, to model the infrared (IR) spectra of various isotopic water solutions with different levels of vibrational couplings, including those that cannot be probed experimentally. Analysis of the different IR OH-stretch lineshapes provides direct evidence for the partially quantum-mechanical nature of hydrogen bonds in liquid water, which is emphasized by synergistic effects associated with intermolecular coupling and many-body electrostatic interactions. Furthermore, we quantitatively demonstrate that intramolecular coupling, which results in Fermi resonances due to the mixing between HOH-bend overtones and OH-stretch fundamentals, are responsible for the shoulder located at ～3250 cm?1 of the IR OH-stretch band of liquid water.
关键词： liquid water,nuclear quantum effects,infrared spectra,Fermi resonances,centroid molecular dynamics,hydrogen bonds,intramolecular coupling,intermolecular coupling,MB-pol potential energy function
更新于2025-09-23 15:21:21
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Reflection coefficient of HfO <sub/>2</sub> -based RRAM in different resistance states
摘要： Impedance spectra of multiple resistive states in a stable-switching Resistive Random-Access Memory device based on a stack of Ru/HfO2/Zr/W was studied in this work. Using these observations, re?ection-coef?cients were extracted for different resistive states. Clear changes in the re?ection coef?cient for different resistive states were observed. The device in a low resistive state showed a signi?cantly higher re?ection coef?cient compared to its high resistive state. An increasing trend in the re?ection coef?cient was observed as the device state was gradually recon?gured towards lower resistances. Maximum frequency for re?ection increased with the decrease in the device area. The physics behind this observation is attributed to the interplay of oxygen ion transport among the interfacial layer, conductive ?lament, and HfO2-?lm.
关键词： resistive states,impedance spectra,HfO2,RRAM,reflection coefficient
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Aqueous Solution Processed Copper Iodide as Hole Transport Material For Planar Inverted Perovskite Solar Cells
摘要： The inorganic carrier transport layers are robust and stable to the environment compared to the organic hole transport layer (HTL). Here, we report on the fabrication of the halide perovskite devices employing CuI as HTL and explored material properties and optoelectronic characterizations. The CuI device demonstrated the device efficiency of 14.1%. The film morphology of CuI is found to have the influence on the perovskite film growth and hence affected on the device parameters. The interface activation energy (EA) ~Eg suggests the recombination activities in the perovskite bulk is dominant. The capacitance analysis revealed the two trap centers of 0.527 eV and 0.332 eV in the perovskite bulk.
关键词： capacitance spectra,interface recombination,defect,copper iodide,halide perovskite
更新于2025-09-23 15:21:01
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The application of proximal visible and near-infrared spectroscopy to estimate soil organic matter on the Triffa Plain of Morocco
摘要： Soil organic matter (SOM) is a fundamental soil constituent. The estimation of this parameter in the laboratory using the classical method is complex time-consuming and requires the use of chemical reagents. The objectives of this study were to assess the accuracy of two laboratory measurement setups of the VIS-NIR spectroscopy in estimating SOM content and determine the important spectral bands in the SOM estimation model. A total of 115 soil samples were collected from the non-root zone (0-20 cm) of soil in the study area of the Triffa Plain and then analysed for SOM in the laboratory by the Walkley–Black method. The reflectance spectra of soil samples were measured by two protocols, Contact Probe (CP) and Pistol Grip (PG)) of the ASD spectroradiometer (350-2500 nm) in the laboratory. Partial least squares regression (PLSR) was used to develop the prediction models. The results of coefficient of determination (R2) and the root mean square error (RMSE) showed that the pistol grip offers reasonable accuracy with an R2 = 0.93 and RMSE = 0.13 compared to the contact probe protocol with an R2 = 0.85 and RMSE = 0.19. The near-Infrared range were more accurate than those in the visible range for predicting SOM using the both setups (CP and PG). The significant wavelengths contributing to the prediction of SOM for (PG) setup were at: 424, 597, 1432, 1484, 1830 ,1920, 2200, 2357 and 2430 nm, while were at 433, 587, 1380, 1431, 1929, 2200 and 2345 nm for (CP) setup.
关键词： soil organic matter,SOM analysis.,VIS-NIR spectroscopy,reflectance spectra,SOM estimation
更新于2025-09-23 15:21:01
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[IEEE 2020 Moscow Workshop on Electronic and Networking Technologies (MWENT) - Moscow, Russia (2020.3.11-2020.3.13)] 2020 Moscow Workshop on Electronic and Networking Technologies (MWENT) - Measurement of the Dynamic Characteristics of Separate Spectral Bands of the LEDs Electroluminescence Spectra
摘要： A method for measuring the 3 dB frequency of the full modulation of separate spectral components of electroluminescence spectrum of light-emitting diodes (LEDs) is described. The method consists in passing through the LED a series of current pulses having the shape of a meander, and the emission spectrum of the LED is measured by a spectrometer OceanOptics USB2000+ in the mode of signal accumulation. As the pulse frequency increases, the intensity of all spectral components of the LED emission spectrum decreases. The frequency at which the optical signal decreases 1.19 times relative to the level measured at a low frequency is taken as the 3 dB frequency of the separate spectral component of the LED electroluminescence spectrum. By using the pulse signal it is possible to increase the sensitivity of the measuring means compared to the measuring means using the harmonic test signal. A description of the hardware-software complex implementing said measurement method is presented. The results of testing the measuring complex by the electroluminescence spectra of commercial green InGaN-based LEDs at the current range of 10-5...10-2 A and the current frequency range of 0.001...10 MHz are presented. The developed hardware-software complex and the method for estimating the spectral recombination parameters of heterojunction LEDs can be used both for the purpose of diagnosing the quality of LEDs and in developing structural and technological solutions for creating new light-emitting structures.
关键词： electroluminescence spectra,measuring complex,measurement method,3 dB frequency,light-emitting diode (LED),radiative and nonradiative charge carriers lifetime
更新于2025-09-23 15:21:01