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Application of polar solvent effects in absorption spectra for determination of lowest electron-excited states of phthalide
摘要： The optical absorption spectra of phthalide in polar (methanol) and nonpolar (n-hexane) solvents are recorded. The electronic phthalide spectrum was calculated by TDDFT B3LYP/6-311+G(d, p) using the polarisable continuum model. Based on an analysis of calculation data and the displacement of absorption bands in a polar solvent, it was established that the absorption bands of phthalide at energies of 3.51 and 3.96 eV correspond to singlet-triplet transitions to the T1 and T2 states, respectively.
关键词： Triplet excited states,Electronic absorption spectra,PCM TDDFT,Solvent effect,Phthalide
更新于2025-09-23 15:23:52
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A novel method for simultaneous determination of zinc, nickel, cobalt and copper based on UV–vis spectrometry
摘要： A novel method based on UV–vis spectrometry is developed for simultaneous determination of zinc, nickel, cobalt and copper without any separation steps. The method studied in this paper is the combination of ratio spectra derivative and kalman filtering spectrophotometry. First, using absorbance of zinc standard solution as divisor, the ratio spectra derivative obtained can completely eliminate the interference of zinc on trace ions. Second, the trace ions are simultaneously determined by kalman filtering spectrophotometry. Last, based on obtaining trace ion concentrations, a calibration curve for zinc is established. The linear determination ranges are 10-70mg/L for zinc, 0.2-1.4mg/L for trace ions of nickel, cobalt and copper. The results show that the predicted results of zinc, nickel, cobalt and copper by this proposed method is superior to PLS method. The work reported here is an effective attempt for the simultaneous determination of zinc, nickel, cobalt and copper in industrial wastewater of zinc hydrometallurgy, and will have more applications.
关键词： Zinc hydrometallurgy,Ratio spectra derivative,Kalman filtering spectrophotometry,UV–vis spectrometry
更新于2025-09-23 15:23:52
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High-temperature mid-infrared absorption spectra of methanol (CH3OH) and ethanol (C2H5OH) between 930 and 1170?cm-1
摘要： A methodology was recently developed with a broad-tuning, rapid-scan external-cavity quantum-cascade-laser in conjunction with shock tube facilities to measure the high-temperature mid-infrared absorption spectra of gaseous molecules. This technique is deployed to measure the cross section profiles in the C-O stretching band for methanol (CH3OH) and ethanol (C2H5OH) between 930 and 1170 cm-1. Methanol spectra are presented from 620 to 1304K between 0.98-3.30 atm with distinctive P, Q, and R branches of the ν8 vibrational band. At elevated temperatures, the emergence of hotbands and high-J ro-vibrational transitions are clearly observed. The absorption cross sections of ethanol are measured from 296 to 1018K between 0.90-3.27 atm. The peak strength decreases with temperature, with the peak location shifting to lower wavenumbers. These measurements are compared with existing empirical models, illustrating a strong need for the development of a high-temperature spectroscopic database.
关键词： Absorption spectra,Ethanol,Mid-infrared,High-temperature,Shock tube,Methanol
更新于2025-09-23 15:23:52
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Extended analysis of FTIR high resolution spectra of HD32S and HD34S in the region of the ν2 band: Positions and strengths of individual lines
摘要： The high resolution infrared spectra of deuterated hydrogen sulfide HDS were recorded with a Bruker IFS125HR Fourier transform infrared spectrometer (Zurich prototype ZP2001) and analyzed in the ν2 fundamental band region, 690–1510 cm?1. 2684 transitions with maximum values of the quantum numbers Jmax.=25 and Kmax.a=17 were assigned in the experimental spectra to the ν2 band (compared to Jmax.=22 and Kmax.a=10 in the preceding analogous studies) of HD32S. On this basis, 415 upper ro–vibrational energies were obtained, which were used then in the weighted fit of the Watson Hamiltonian parameters. 33 parameters obtained from the fit reproduce the 415 initial energy values with a root mean square deviation drms=1.1×10?? cm?1. An analysis of 418 experimental ro–vibrational line intensities of the ν2 band of HD32S was made using the Hartmann–Tran profile of individual lines, and results were applied in the fit of parameters of the effective dipole moment operator. Isotopic relations for the dipole moment parameters were derived and used for the fit procedure. The obtained 'model' parameters reproduce the initial line strengths with the drms=4.7%. A list of 2684 experimental transitions of HDS is generated together with the presentation of their individual line strengths predicted on the basis of the obtained effective dipole moment parameters. An analogous analysis was fulfilled for the ν2 band of the HD3?S isotopologue.
关键词： HD32S,isotopic substitution,FTIR,ν2 band,line positions,HD34S,high resolution spectra,line strengths,spectroscopic parameters
更新于2025-09-23 15:23:52
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Prediction model optimization using full model selection with regression trees demonstrated with FTIR data from bovine milk
摘要： Predictive modeling is the development of a model that is best able to predict an outcome based on given input variables. Model algorithms are different processes that are used to define functions that transform the data within models. Common algorithms include logistic regression (LR), linear discriminant analysis (LDA), classification and regression trees (CART), na?ve Bayes (NB), and k-nearest neighbor (KNN). Data preprocessing option, such as feature extraction and reduction, and model algorithms are commonly selected empirically in epidemiological studies even though these decisions can significantly affect model performance. Accordingly, full model selection (FMS) methods were developed to provide a systematic approach to select predictive modeling methods; however, current limitations of FMS, such as its dependency on user-selected hyperparameters, have prevented their routine incorporation into analyses for model performance optimization. Here we present the use of regression trees as an innovative method to apply FMS. Regression tree FMS (rtFMS) requires the development of a model for every combination of predictive modeling method options under consideration. The iterated, cross-validation performances of these models are then passed through a regression tree for selection of a final model. We demonstrate the benefits of rtFMS using a milk Fourier transform infrared spectroscopy dataset, wherein we build prediction models for two blood metabolic health parameters in dairy cows, nonesterified fatty acids (NEFA) and β-hydroxybutyrate acid (BHBA). The goal for building NEFA and BHBA prediction models is to provide a milk-based screening tool for metabolic health in dairy cattle that can be incorporated automatically in milk analysis routines. These models could be used in conjunction with physical exams, cow side tests, and other indications to initiate medical intervention. In contrast to previously reported FMS methods, rtFMS is not a black box, is simple to implement and interpret, it does not have hyperparameters, and it illustrates the relative importance of modeling options. Additionally, rtFMS allows for indirect comparisons among models developed using different datasets. Finally, rtFMS eliminates user bias due to personal preference for certain methods and rtFMS removes the dependency on published comparisons of methods. Thus, rtFMS provides clear benefits over the empirical selection of data preprocessing options and model algorithms.
关键词： Prediction model,Fourier-transform infrared spectra,Regression tree,Preprocessing,Full model selection
更新于2025-09-23 15:23:52
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Comparative investigations of gadolinium based borate glasses doped with Dy3+ for white light generations
摘要： Gadolinium-based borate glasses doped with Dy3+ ions were developed by melt quenching technique for white light generation. The title glasses were examined by XRD, optical absorption spectra and Photoluminescence spectra. From photoluminescence emission spectra, the higher intensity peak was observed at 575 nm (4F9/2 → 6H13/2) for present glass samples. The experimental decay rate (τexp) of 4F9/2 transition of Dy3+ ions were found to be a decline in increasing of Dy2O3 content. The Inokuti-Hirayama (IH) model is used to explain the non-exponential decay time by putting S=6, which confirmed that the energy is transfer through cross-relaxation is of dipole–dipole nature among the Dy2O3. The values of color coordinates match with the range of white light of chromaticity (CIE) diagram. The color chromaticity coordinates (u, v) and color correlated temperature (CCT) values for present glasses were correlated with standards, which are closely related to the standard, therefore, the prepared glasses might be helpful for different photonic applications such as white LEDs.
关键词： luminescence,glasses,borate,spectra,Gadolinium
更新于2025-09-23 15:23:52
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Band structure and optical constants of SnS <sub/>2</sub> single crystals
摘要： Absorption (K), reflection (R) and wavelength modulated transmission (ΔT/Δλ) spectra in SnS2 crystals of hexagonal phase (space group P63/mmc) were investigated in temperature interval from 300 to 10 K. It was established that indirect band gap (Eg ind - 2.403 eV) is due to unpolarized indirect transitions between Γ and M points of Brillouin zone. A minimal direct band gap (Eg dir - 2.623 eV) in E||b polarization is formed by direct allowed transitions and in E⊥b polarization (2.698 eV) by forbidden transitions in Γ point of Brillouin zone. A magnitude of refractive index (n) changes from 3 to 4 and has a maximum at 2.6 eV. Optical functions (n, k, ε1 and ε2) in energy region E > Eg (3 - 6.5 eV) were calculated from measured reflection spectra by Kramers-Kronig analysis. Features observed in reflection and optical function spectra were assigned to electron transitions. This electron transitions were localized in framework of theoretically calculated band structure.
关键词： optical functions,electronic band structure,layered SnS2 crystals,absorption, reflection and transmission spectra
更新于2025-09-23 15:23:52
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H-complexes in the “4-n-alkoxybenzoic acid: 4-pyridyl 4′-n-alkoxybenzoate” system. IR spectroscopy and quantum chemical calculations
摘要： IR spectra of individual 4-n-dodecyloxybenzoic acid (A) and 4-pyridyl 4'-n-dodecyloxybenzoate (B) compounds as well as IR spectra of 2A:1B and 1A:1B systems were recorded. For the assignment of the experimental vibrational spectra a series of quantum chemical calculations of DFT(B97-D)/6-311++G** level was carried out. Hydrogen-bonded complexes of types A···A, A···B, as well as various trimers that can be formed at different component ratios in system A-B were simulated. The geometric structure of these complexes was optimized and the vibrational frequencies were calculated. The conclusions on the molecular organization of system A-B for different ratios of the components A and B were based on the interpretation of IR spectra and the analysis of calculated thermodynamic characteristics of self-assembly processes. Thus, it is determined that the system A consists of cyclic A···Acycl dimers; in 1A:1B system the H-complexes of A···B type are formed. In the 2A:1B system in the process of self-assembly, instead of the complexes A···A···B and A···B···A of stoichiometric composition, the complexes A···B and A···Acycl are formed in the ratio 2:1. These results are confirmed by the dilatometric method data.
关键词： thermodynamic characteristics,4-pyridyl 4'-n-alkoxybenzoate,DFT,IR spectra,self-assembly,4-n-alkoxybenzoic acid,hydrogen bonded complexes
更新于2025-09-23 15:23:52
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Prediction of Structural, Vibrational and Nonlinear Optical Properties of Small Organic Conjugated Molecules Derived From Pyridine
摘要： Nonlinear optical (NLO) effects of organic materials are caused by delocalized electrons and large polarization in molecules. In the present work, theoretical study by using the Density Functional Theory (DFT) at B3LYP/6-311G(d,p) level of theory on three types of pyridine derivates 2,6-dimethoxy-3,5-dinitropyridine (M1), 2-methoxy-3-nitropyridine (M2) and 2-methoxy-5-nitropyridine (M3) is reported. The nuclear magnetic resonance (1H- and 13C-NMR) chemical shifts of the title compounds were calculated using the Gauge Independent Atomic Orbital (GIAO) method and compared to the observed results. Both infrared absorption and Raman are complementary to provide characteristic fundamental vibrations that are necessary for the identification of the molecular structures. Electronic properties such as frontier molecular orbital (HOMO, LUMO), ionization potential (IPad) and electronic affinity (EAad) were determined to get better insight into the molecular properties. Using the Time-Dependent Density Functional Theory (TD-DFT), electronic absorption spectra have been predicted and closely matching the experimental findings. The natural bonding orbital (NBO) calculations were performed in order to elucidate various second order interactions in between the filled and vacant orbitals which are a measure of the intermolecular as well as the delocalization within the molecule. In addition, we have demonstrated that these molecular systems have large first static hyperpolarizabilities and may have potential applications in the development of NLO materials.
关键词： NLO properties,Electronic properties,DFT,Optical spectra,NBO
更新于2025-09-23 15:23:52
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Resonance reflection of light by ordered silicon nanopillar arrays with the vertical p-n junction
摘要： Silicon nanopillar (Si NP) arrays with the axial p-n junction were formed and investigated. A method to fabricate Si NP ordered arrays by means of electron beam lithography using the negative electron resist and reactive ion etching is presented. The effect of strong resonance light scattering – change of the color of separate Si NPs - was demonstrated. One or several minima were registered in the measured reflection spectra. Thereat, the position of reflection minimum was changed with a change in Si NP diameter. A shift of the minimum position towards the longer wavelength spectral region with an increase in Si NP diameter was observed. A shift of the position of minima to the shorter wavelength spectral region with a decrease in Si NP pitch in microarrays with the same Si NP diameter was observed. The quantitative divergence in the position of reflection minima in Si NPs with calculated dependencies for Mie resonances was found. High photosensitivity of Si NP arrays with axial p-n junction to visible and near IR light was discovered. So, these structures may be used for selective photonic sensors.
关键词： reflectance spectra,silicon nanopillars,electrophysical properties,reactive ion etching,electron beam lithography
更新于2025-09-23 15:23:52