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Tracking small heterogeneity in binary mixtures of aliphatic and aromatic hydrocarbons: NIR spectroscopic, 2DCOS and MCR-ALS studies
摘要： To our best knowledge, this is the ?rst spectroscopic study of small heterogeneity at a molecular level in binary mixtures of aliphatic and aromatic hydrocarbons. The composition-dependent spectra of benzene/toluene, benzene/n hexane, benzene/cyclohexane, n hexane/n heptane and n hexane/cyclohexane mixtures were recorded by NIR transmission technique in the whole range of mole fractions. A comprehensive exploration of the experimental data was performed by two-dimensional correlation analysis (2DCOS) and chemometric methods. In addition, we calculated excess NIR molar absorption spectra and parameter of ER, which allows for comparison of the degree of deviation from ideality for various mixtures. Our results reveal that all studied mixtures deviate from the ideal mixture. The extent of these deviations is small for the mixtures were both components are aromatic or aliphatic and increases for aromatic/aliphatic mixtures. In addition, molecular shapes have an important effect on the degree of deviation from the ideal mixture. As expected, benzene/n hexane is the most non-ideal mixture, while behavior of n hexane/n heptane and benzene/toluene mixtures is close to the ideal one. Our results suggest that in the mixtures with the largest deviations from ideality are present homoclusters of both components and heteroclusters. The heteroclusters exist in the whole range of compositions, while the homoclusters appears above a certain concentration limit. If both components of the mixture are similar, the molecules with equal probability form the homo- and heteroclusters. In the case of unlike components, the molecules prefer to form the homoclusters. The homoclusters of both components in the mixture are similar as those observed in bulk constituents. This means that deviation from the ideal mixture results from presence of the heteroclusters.
关键词： Aliphatic/aromatic hydrocarbons,NIR,Clustering,MCR-ALS,Binary mixtures,2DCOS,Chemometrics,Excess absorption spectra,Microheterogeneity
更新于2025-09-19 17:15:36
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Electron correlation effects in the photoionization of CO and isoelectronic diatomic molecules
摘要： This paper investigates the first sigma satellite band, which is by far the most prominent, in the valence photoelectron spectra for a set of isoelectronic diatomic molecules: carbon monoxide, carbon monosulfide, carbon monoselenide, silicon monoxide and boron monofluoride. In particular, we analyze the effect of the electronic structure, with the change of the atomic pair along the row and column of the periodic table on the position of the satellite peak as well as on the related dynamical observables profiles. For this investigation, highly correlated calculations have been performed on the primary ionic states and the satellite band for all the molecules considered. Cross sections for the primary ionic states, calculated using Dyson orbitals, have been compared with those obtained with Hartree–Fock and Density Functional Theory to probe the impact of the correlation in the bound states on the photoionization observables. Limitations of a simple intensity borrowing mechanism clearly result from the analysis of the satellite state, characterized by different features with respect to the relevant primary states.
关键词： isoelectronic molecules,photoelectron spectra,photoionization,electron correlation,Dyson orbitals
更新于2025-09-19 17:15:36
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MgF2-Based Luminescing Ceramics
摘要： Results of investigation at 300 K of photo- and cathodoluminescence of the high-temperature optical ceramics synthesized for the first time based on MgF2 activated tungsten oxide are presented.
关键词： luminescence,tungsten,ceramics,magnesium fluoride,excitation spectra,annealing
更新于2025-09-19 17:15:36
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Effect of yttrium insertion on the structural, optical, vibrational and dielectric properties of 0.3Bi1?yYyFeO3–0.7Ba0.8Sr0.2TiO3 ceramics
摘要： Perovskite ceramics [Ba0.8Sr0.2]1-x[Bi1-yYy]xTi1-xFexO3 with x = 0.3 and 0.05 \ y \ 0.15 are synthesized by solid-state solution in order to study the effect of yttrium insertion on the physical properties of this material. The XRD patterns showed the formation of single tetragonal phase without any impurities. Using UV–Vis spectroscopy, the absorbance and re?ectance are highlighted. In fact, we note a blueshift on wavelength and the energy band gap is increased with a high doping content. Besides, Raman spectra display a drop in mode intensities, which is followed by the rise of yttrium that can lead to a ?uctuation in the atomic structure. Furthermore, the permittivity and loss dielectric are studied by impedance spectroscopy, revealing that both decrease with rising frequency indicating, as a result, a dielectric dispersion. Finally, the study of permittivity dielectric as a function of temperature exhibits the presence of G-type antiferromagnetic transition.
关键词： Structural analysis,Ba0.8Sr0.2TiO3,Dielectric response,Optical properties,Solid-state reaction,BiFeO3,Raman spectra
更新于2025-09-19 17:15:36
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Lawsone isomers, lawsone ether and bilawsone for dye-sensitized solar cells applications: DFT and UV–Vis studies
摘要： Structural and optoelectronic properties of lawsone (L), lawsone ether (LE) and bilawsone (BL) were studied theoretically using the DFT and time-dependent DFT methods with hybrid functional B3LYP5 and 6-311G (2d,p) basis set. For the monomer lawsone molecule, isomerization reaction between two rotational isomers was analyzed based on a thermodynamic approach. The electronic spectra of the dyes molecules in a vacuum and solvents (DMSO and CH2Cl2) were computed. The maximum wavelengths were found at 355e408 nm for the LE and 350e448 nm for BL that indicated bands shift to visible range compared to L (340 nm). The UVeVis spectra of the L and BL were measured experimentally in DMSO solution. For the BL, a broad and intensive band was observed in a visible region at 452 nm that apparently would favour sensitizing ability of the dye. The optoelectronic properties of the LE and BL showed them as more promising candidates for DSSCs applications compared to the individual lawsone dye.
关键词： Lawsone ether,Dye-sensitized solar cells,Lawsone isomers,DFT/TD-DFT,Bilawsone,UVeVis/vibrational spectra
更新于2025-09-19 17:13:59
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Halogen detection with molecular laser induced fluorescence
摘要： The detection of low halogen concentrations by atomic Laser Induced Breakdown Spectroscopy (LIBS) is usually difficult due to the weak lines, which overlaps with matrix and due to an uncomfortable spectral region. Molecular LIBS (MLIBS) based on diatomic molecules of halogens with alkali earth element emission substantially increases sensitivity for halogen detection. We demonstrate that the Molecular Laser Induced Fluorescence (MLIF) method allows one to further increase the halogen detection approach. Practical application of the LIBS-MLIF method is demonstrated on Cl atom detection in concrete samples.
关键词： laser-induced plasma spectroscopy,diatomic molecular spectra
更新于2025-09-19 17:13:59
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Calculation of the extreme-ultraviolet radiation conversion efficiency for a laser-produced tin plasma source
摘要： This article presents the calculation results on the conversion efficiency (CE) of 1.064 μm laser-produced plasmas (LPPs) extreme-ultraviolet (EUV) tin (Sn) light sources with the Gaussian and a triangular-flat-topped like laser pulse temporal shapes. The computational model includes a collisional-radiative model and 1D hydrodynamics code that predicts reported experimental and theoretical results on the CE of 1.064 μm and 10.6 μm LPP EUV sources with the planar and mass-limited spherical Sn targets. The calculations for the case of a spherical target reveal that an optimum triangular-flat-topped like laser pulse generates a higher CE compared to the Gaussian pulse, especially, for the longer laser pulse duration than ~30 ns. The study demonstrated that a rising intensity rate of the laser pulse has a vital role to optimize the CE as well as to prolong the in-band (13.5 ± 0.135 nm) spectral emission of a small Sn spherical target. The model predicts a ~30 ns rising time duration for a linearly increasing intensity of triangular-flat-topped 1.064 μm laser pulse is necessary to obtain a maximum CE with a typical ~40 μm diameter liquid Sn droplet.
关键词： Extreme-ultraviolet lithography,Collisional-radiative model,Laser-produced plasmas,Radiation-hydrodynamics,Highly-charged tin spectra
更新于2025-09-19 17:13:59
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In-situ Monitoring on Micro-hardness of Laser Molten Zone on AISI4140 Steel by Spectral Analysis
摘要： The real-time monitoring technology plays a significant role in the field of laser aided manufacturing. It not only ensures the product quality, but also saves time and expenditure on the subsequent testing. To develop a method to monitor the properties of laser molten zone, in this paper, the AISI4140 steel samples were melted by laser with different parameters. At the same time, the plasma spectra were detected during real-time laser processing. The evolutions for both emission spectra and hardness of molten zone were researched in this work. To correlate the intensity of spectral line with the hardness of molten zone, the method of dimensionless analysis was used in this experiment. As the results shown, in a dimensionless system, there was a linear correlation between dimensionless micro-hardness of molten zone (H*) and dimensionless laser energy density(ln(δ*)); the dimensionless micro-hardness could be expressed by a piecewise function using dimensionless intensity of Fe I spectral lines(I*), dimensionless velocity(v*) and dimensionless laser energy density as variables; depending on the quantitative relation among all dimensionless, a monitoring system of hardness of molten zone was established; by testing under different parameters of laser processing, the mean error of prediction is lower than 3.1%. It means the emission spectroscopy can be a potential way to monitor the properties of parts prepared by laser processing.
关键词： AISI4140 steel,plasma spectra,laser aided manufacturing,micro-hardness,dimensionless analysis,real-time monitoring
更新于2025-09-19 17:13:59
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Sub-400 nm film thickness determination from transmission spectra in organic distributed feedback lasers fabrication
摘要： The design and fabrication of thin-film based organic optoelectronic devices require knowledge of the film optical properties. A low-cost and non-destructive method often used for optical characterization of films is the well-established spectrophotometric envelope method. However, this method is typically limited to thickness above 400 nm, a value often higher than that of the films involved in these devices. This paper studies a procedure to obtain the thickness of sub-400 nm active films from their spectrophotometric trace when the refractive index is previously known. The proposed procedure is based on comparing the experimental transmission spectrum in the transparent spectral window with that obtained by simulation. The capabilities of the proposed method are demonstrated here by its application in the fabrication of organic distributed-feedback lasers where a fine control of film thickness is important to obtain an optimized and reproducible response. Results were verified with other techniques, such as ellipsometry and profilometry. Thus, with the proposed method, film thickness can be easily determined down to 40 nm maintaining an accuracy of about 5 nm even for films with low refractive index (1.5-1.7). Different methods to determine refractive index of these films are also discussed.
关键词： Optical characterization,Thin film thickness,Transmission spectra,Distributed feedback lasers
更新于2025-09-19 17:13:59
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Substitutional effect of different bridging groups on optical and charge transfer properties of small bipolar molecules for OLEDs
摘要： In this work, a series of eight different bipolar molecules were designed and calculated using density functional theory (DFT) and time‐dependent functional theory (TD‐DFT) for organic light emitting diodes (OLEDs) as efficient luminescent and charge transfer materials. The eight donor‐π‐donor type small molecules (D1‐D8) were composed of triphenylamine (TPA) donor (D) unit connected to 1,8‐naphthalimides (NI) acceptor (A) unit though different π‐conjugated or R‐groups (as π‐spacer). The effect of substitutions made in π‐spacer was investigated on optical, electronic, and stability properties. This calculation analysis showed that different substitutions in π‐spacer resulted smaller Eg (range from 1.63 to 2.00 eV), broader absorption with the lowest excitation energy covering both visible and near infrared regions of solar spectrum, especially D3, D4, D5, and D6 molecules. The analyses of local densities of states, frontier molecular orbitals, and natural population analysis of orbitals revealed that studied molecules exhibited π‐π* electronic transitions of absorption in singlet excited states, but D5 and D6 also show intramolecular charge transfer (ICT) characteristics. The study of chemical indices, molecular electrostatic potential (MEP) surfaces, and charge transfer properties turned out that D4, D5, and D6 are expected to show good potential for luminescent and hole transport materials in the favor of OLEDs.
关键词： DFT,organic light emitting diodes (OLEDs),optical properties,absorption spectra,electronic structures
更新于2025-09-19 17:13:59