Optical Spectral Data Research Articles

Synthesis, Studies of Inorganic Class of Mohrite (MOH) Crystals for Electrical, Electronic, Photonic, Phase Matching and Sensor Utilities by Theory and Practice

The high-quality single crystals of Mohrite (MOH) with dimensions 7 × 6 × 3 mm3 were productively grown-up by the customary solution growth methodology. The fully grown crystals were focused to the appropriate structural, optical and electrical investigations. The MOH is monoclinic nature of the specimen with P21/c as the space group and lattice parameters are a as 6.2385 Å, b as 12.6076 Å, c as 9.2655 Å and beta is 106.526°. The crystalline structural authentication with single crystal XRD analysis and compared the same with software based associated results. FITR spectra reveal the vibrational modes of as grown crystals. Optical absorption spectral data divulges that the as-grown crystalline sample has higher optical transparent nature in the visible-NIR region. Photoluminescence intensity is remarkably enriched, shows high crystallinity of MOH. The results of UV, PL, electrical and photo conductivity, SEM, theoretical studies suggest MOH in photonic utility and device appliances especially in UV filters and in electronic filters, room temperature based sensor study for MOH is enabled and reported for red LED based work.

Experimental investigation of machine-learning-based soft-failure management using the optical spectrum

The demand for high-speed data is exponentially growing. To conquer this, optical networks have undergone significant changes, getting more complex and versatile. The increasing complexity necessitates that the fault management be more adaptive to enhance network assurance. In this paper, we experimentally compare the performance of soft-failure management of different machine learning algorithms. We further introduce a machine-learning-based soft-failure management framework. It utilizes a variational autoencoder-based generative adversarial network (VAE-GAN) running on optical spectral data obtained by optical spectrum analyzers. The framework is able to reliably run on a fraction of available training data as well as identify unknown failure types. The investigations show that the VAE-GAN outperforms the other machine learning algorithms when up to 10% of the total training data are available in identification tasks. Furthermore, the advanced training mechanism for the GAN shows a high F1-score for unknown spectrum identification. The failure localization comparison shows the advantage of a low complexity neural network in combination with a VAE over established machine learning algorithms.

Effect of the charge-separated state on the 3MLCT state: Synthesis and study of the photophysics of electron donor-acceptor dyads based on Pt(II)-Schiff base coordination framework and naphthalenediimide chromophore

We prepared Pt(II)-Salen Schiff base complexes with a naphthalenediimide (NDI) unit attached on the coordination framework, to study the intersystem crossing (ISC), the charge separation, and the possible formation of a long-lived triplet charge separated (CS) state. The Pt(II)-Schiff base coordination framework acts as electron donor and it shows ultrafast ISC (<1 ps) and small Stokes shift. NDI acts as electron acceptor. The two units are attached either via a phenyl linker (Pt-NDI) or phenyl ethynyl linker (Pt-CC-NDI). Negligible electronic interaction between the Pt(II)-Schiff base coordination framework and the NDI unit at ground state was observed for both dyads, whereas the phosphorescence of the Pt(II)-Schiff base coordinated framework was quenched to large extent in the dyads, as compared to the reference complexes containing no NDI unit, especially in polar solvents. Electrochemical and optical spectral data show that the CS state energy is 1.93 eV, 1.82 eV, 1.54 eV, 1.43 eV in n-hexane (HEX), toluene (TOL), tetrahydrofuran (THF), acetonitrile (ACN), respectively. In comparison, the 3MLCT state and 3NDI state energy are 1.97 and 2.04 eV, respectively. Nanosecond transient absorption spectra show the formation of the 3MLCT state for Pt-CC-NDI, whose lifetimes is shortened in polar solvents (τT = 3.5 µs, 2.1 µs, 22 ns, and 19 ns in HEX, TOL, THF and ACN, respectively), similar trend was observed for Pt-NDI. Femtosecond transient absorption spectra show that the charge separation takes less than 1 ps both in toluene and acetonitrile. Quenching of the otherwise long-lived triplet excited state (3.5 µs) by a short lived CS state may be developed as a photo-protection mechanism similar to that found in natural photosynthetic apparatus.

HINOTORI I: The nature of rejuvenation galaxies

Abstract We present the HINOTORI (Star Formation History Investigation To Find Rejuvenation) project to reveal the nature of rejuvenation galaxies (RGs), which are galaxies that restarted their star formation after being quiescent. As the first step of HINOTORI, we construct the largest RG sample with 1071 sources. We select these RGs from 8857 MaNGA (Mapping Nearby Galaxies at APO) survey galaxies by reconstructing their star formation histories with the Prospector spectral energy distribution fitting code. Both optical spectral data and UV to IR photometric data are used for the fitting. Using mock data, we confirm that our method can detect weak rejuvenation events that form only about $0.1$% of the total stellar mass with high completeness. The RGs account for ${\sim}10$% of the whole sample, and rejuvenation events contribute on average only about $0.1$% of the total stellar mass in those galaxies but $17$% of the cosmic star formation rate density today. Our RGs have a similar mass distribution to quiescent galaxies (QGs). However, the morphology of the RGs is more disk-like than QGs, suggesting that rejuvenation may occur selectively in disk-like QGs. Our results also suggest the possibility of multiple-time rejuvenation events in a single galaxy. Further spatially resolved analyses of integral field unit data and radio observations and comparisons to simulations are needed to identify the mechanism and the role of rejuvenation in galaxy evolution.

Investigating the impact of plasma nitriding on Ti6Al4V surface, structural, and mechanical properties and their simultaneous evaluation via laser opto-ultrasonic dual detection (LOUD) approach

Titanium alloys possess exceptional properties, but due to their poor surface characteristics, several engineering processes have been developed to modify surface properties. Surface modification methodologies such as plasma nitriding exhibit a favourable pathway to improve these properties. This study investigates the impact of plasma nitriding on surface properties and their evaluation via the laser opto-ultrasonic dual detection (LOUD) technique. The scanning electron microscope, X-ray diffraction, and tensile testing results showed that with the increase in nitride plasma power density from 1.42 to 10.0 × 102 W/cm2, a substantial variation in microstructure and phase transformation occurs, eventually refining the grain size, increasing the hardness from 310.83-HV5.0 to 745.50-HV5.0 and elastic modulus (E) from 115.26 to 128.35 GPa, respectively. Furthermore, these characteristics were assessed concurrently through ultrasonic and optical signal processing for LOUD detection. The results of G.S and E from the acoustic attenuation coefficient and longitudinal and shear wave velocities are reliable with the results of conventional optical microscopy and tensile testing with (R2 ≥ 0.996). Meanwhile, the optical spectral data were analyzed to determine the hardness. The results showed that the calibration curve of the intensity ratios (Ti-II/Ti-I) and plasma electron temperature exhibited a linear relationship with hardness (R2 ≥ 0.989), which showed a good approximation.

An approach to characterize the compositional, structural and mechanical properties of thermally processed titanium (Ti) alloy simultaneously via novel in-situ laser opto-ultrasonic dual detection (LOUD)

A keen interest is developed in improving heat treatment methods of Ti alloy to meet the desirable mechanical properties due to its enhanced physical and chemical features. Structural and mechanical properties are important parameters as they are significantly affected by heat treatment and process conditions. However, most metal manufacturer relies on separate post-process analysis, which is usually time-consuming, costly, and destructive. Therefore, this study investigated a novel in-situ laser Opto-ultrasonic dual detection (LOUD) approach for real-time analysis of the elemental composition, grain size distribution, and hardness simultaneously of heat-treated Ti6AL4V alloy. The X-ray diffraction (XRD) and scanning electron microscope (SEM) results showed that with the increase in annealing temperature and cooling rate, a pronounced change in microstructure and phase transition occurs, eventually increasing grain size and hardness, respectively. The elemental composition, grain size distribution, and hardness variations were evaluated simultaneously via the processing of ultrasonic and optical signals in in-situ LOUD detection. The obtained results of average grain size from the ultrasonic acoustic attenuation of all the investigated samples are consistent with the results of optical microscope (OM) maps with a good regression coefficient value (R2 ≥0.991). Meanwhile, the optical spectral processing data for hardness analysis exhibited that the calibration curve of the emission intensity ratio (Ti-II/Ti-I) and plasma electron temperature (Te) is linearly dependent on hardness with (R2 ≥0.994). The linear correlation results of ultrasonic acoustic attenuation with grain size, calibration curve, and Te with the hardness investigated via the in-situ LOUD technique shows good approximation, ensuring quality control and reliability.

An Optical Overview of Blazars with LAMOST. II. Gamma-Ray Blazar Candidates and Updated Classifications

Abstract Blazars represent the dominant class of associated γ-ray sources detected by the Fermi Large Area Telescope (LAT). However, in the more recent release of the Fourth Fermi-LAT Point Source Catalog (4FGL), ∼25% of the sources associated with lower-energy counterparts show a multifrequency behavior similar to that of blazars, but lacks an optical spectroscopic confirmation of their nature and are therefore classified as Blazar Candidates of Uncertain Type (BCUs). A particularly challenging task in blazar studies is to classify these BCUs and, when possible to estimate their redshifts, in particular for BL Lac objects, characterized by almost featureless optical spectra with only weak emission lines. Continuing our study of blazars with Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) optical spectral data, we perform an extensive search for optical spectra available in the LAMOST Data Release 6 archive. Our aim is confirming the blazar nature of BCUs and to test if new data can allow us to get a redshift estimate for BL Lac objects that lack measurement, as well as to search for and discover changing-look blazars. We selected sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified and/or unassociated γ-ray sources, and the Roma-BZCAT multifrequency catalog of blazars, finding a total of 42 sources with available LAMOST DR6 spectra. We confirmed the blazar-like nature of four blazar candidates . For the remaining 37 sources we confirm their previous classification.

Effect of melting condition on optical, FTIR and E.S.R properties of irradiated fluorophosphate glasses containing vanadium ions

Glasses from the system Na2O–CaF2–P2O5 with varying doping V2O5 (0.5, 0.75, 1%) were prepared under ordinary and reducing conditions. Multiple Characterizations including optical, FTIR and ESR spectral data were obtained for the prepared glasses before and after gamma irradiation (with a dose of 6 Mrad).Optical absorption spectrum of the undoped sample reveals strong and broad UV absorption with two peaks which are related to unavoidable traces of iron (Fe3+) ions contaminated within the chemicals used for the preparation of the glasses. The V2O5 doped glasses show two additional pronounced broad visible and near-IR bands which varied in intensity and position of their peaks with the V2O5 content and condition of melting. These distinct visible and near IR bands are assumed to be indicator for the presence for low valence trivalent and tetravalent vanadium ions with variable percents, in accordance with the included host fluoro-phosphate glass and different melting conditions. Gamma irradiation causes noticeable effect on the optical spectrum of the undoped glass but the spectra of V2O5-doped samples reveal pronounced shielding behavior. FTIR spectra of the prepared glasses show distinct vibrational bands due to asymmetric and symmetric vibrations of the phosphate groups of main (PO4) groups and together with the presence of some (PO3F) groups. The detailed FTIR spectra show minor variations with the V2O5 content or condition of melting. E.S.R results show distinct signals due to the presence of both trivalent and tetravalent vanadium ions which possess unpaired electrons in their outer electronic configurations. E.S.R data reveal limited variations in the intensity of the signals with varying V2O5 content or condition of melting and even upon gamma irradiation points out to the stability of V3+ and V4+ ions in the studied host fluorophosphate glass.

Synthesis, spectral and thermo-kinetics explorations of Schiff-base derived metal complexes

AbstractSchiff-base ligand, 2,6-bis(benzimino)-4-phenyl-1,3,5-triazine (L), and its transition metal complexes of Co(ii), Ni(ii), and Cu(ii) were synthesized by refluxing the reaction mixture and its analytical, spectral, and thermogravimetric characteristics were explored by various techniques: AAS, FT-IR, UV-vis, TG-DTG, CHNS/O, and VSM. It was observed that all the metal containing complexes are non-electrolytic, mononuclear, and paramagnetic in nature, confirmed by the molar conductance and magnetic susceptibility measurements. Optical spectral data were used to investigate the geometrical and spectral parameters of [Co(L)(ac)2], [Ni(L)(ac)2], [Cu(L)(ac)2], [Cu(L)(acac)2], and [Cu(L)(fmc)2] complexes. Simultaneous thermal analyses (TG-DTG) in nitrogen atmosphere reveal that the ligand decomposes in one step, [Co(L)(ac)2], [Ni(L)(ac)2], and [Cu(L) (ac)2] complexes are decomposed in three steps, whereas [Cu(L)(acac)2] and [Cu(L) (fmc)2] are decomposed in five and two steps, respectively. In addition, activation energy (Ea) and pre-exponential factor (ln A) were evaluated by TG-DTG decomposition steps of compounds using the Coats–Redfern formula. Enthalpy (∆H), entropy (∆S), and Gibbs free energy (∆G) of the as-prepared metal complexes were also speculated by various thermodynamic equations.

Structural and Optical Study of CoO Doping in Borophosphate Host Glass and Effect of Gamma Irradiation

A series of borophosphate based glasses were prepared with a main composition (50P2O5–30B2O3–10CaO–10Na2O ) wt%. The effect of addition wt% (of cobalt oxide (0.2, 0.5, 0.7) g in different forms is the main purpose of this study. Structural and optical properties of the prepared glasses were obtained using both FITR and UV–Visible techniques. The optical band gap was evaluated from the optical absorption spectral data. XRD was investigated to indicate the formed phases of prepared systems. Density measurements also were done using Archimedes method. The effect of successive gamma irradiation by various doses (10, 30, 50 KGy not) on the different properties of the prepared glasses were measured.

Estimation of the spatial distribution of spring barley yield using ground-based and satellite spectrophotometric data

The article presents a method for estimating the spatial distribution of spring barley yield, based on the use of optical ground and satellite spectral data (PlanetScope data with a spatial resolution of 3 meters). This approach is highly relevant for the development of precision agriculture technologies. Yield mapping is carried out on the basis of data on the spatial distribution of the actual yield and the spatial distribution of the spectral optical characteristics. The method’s characteristic feature is the use of the integral values of vegetation indices (NDVI, MSAVI2, ClGreen) at various stages of crop development. The method was tested on the basis of stationary field experience, where traditional agriculture (deep plowing) is compared with resource-saving technologies (subsurface and surface plowing, and direct seeding with zero tillage).

United calculation of the optical and EPR spectral data for Co2+-doped CdS crystal

This article reports a united calculation of the optical band positions and EPR parameters (g factors g//, g⊥ and zero-field splitting D) for Co2+ ion at the trigonal tetrahedral Cd2+ site of CdS crystal by using the complete diagonalization (of energy matrix) method built on the cluster approach. In the approach, the one-electron basis functions are the molecular orbitals composed of the d orbitals of central dn ion and p orbitals of ligands (rather than only the pure d orbitals in the conventional crystal-field theory), and so the contributions from not only the spin-orbit parameter of dn ion, but also that of ligand ion are contained. The calculated results are in rational agreement with the twenty-two (nineteen optical band positions and three EPR parameters) observed spectral values found in the literature. The defect structure (particularly, the angular distortion) of the trigonal Co2+ center in CdS: Co2+ is also acquired by the calculation. The outcomes are discussed.

Preparation and characterization of invert glasses with high CdO content

Glasses from the binary CdO-B2O3 system were prepared with extended invert compositions containing high CdO content (50–90 mol%) by melting followed by annealing technique. Combined optical and FTIR spectral measurements were carried out to find out the structural constitution of the studied invert glasses and their suitability in optical purposes. Optical spectral data reveal distinct UV absorption due to unavoidable trace iron impurities. FTIR spectra indicate the role of CdO to convert some BO3 to BO4 groups as many of alkali and alkaline earth oxides. The IR spectra reveal distinct vibrational peaks due to BO3 and BO4 units within their specific different wavenumbers. At high CdO, the IR spectra reveal the possible sharing of vibrational peaks due to Cd-O, Cd-O-B or CdO4 as evidenced by the reference IR for crystalline CdO. Thermal expansion and density measurements show some changes which can be related to suggested behavior of Cd2+ ions. With high percent, CdO is assumed to behave as modifier beside forming CdO4 groups. The change in the role of CdO is also assumed to explain the variations in both the density and thermal expansion data. Such observed changes in both the density and thermal expansion are quite different than the borate anomaly identified in the thermal expansion data of alkali borate glasses and are identified at high CdO content.

A uniform research on the optical and EPR spectral data for the trigonal Cr3+ center in Cr3+-doped Ca3Ga2Ge3O12 garnet

This article represents a uniform calculation for the optical and electron paramagnetic resonance (EPR) spectral data of the trigonal Cr3+ center in Cr3+-doped Ca3Ga2Ge3O12 (CGGG) garnet crystal by using the full diagonalization (of energy matrix) method. The method is built on the two-spin-orbit-parameter model where the contributions due to both the spin-orbit parameter of central dn ion in the traditional crystal-field theory and that of ligand ion via covalence effect are comprised. The calculated results indicate that the observed ten optical and EPR data (seven optical bands and three EPR parameters g//, g⊥, D) can be rationally interpreted by this method with only four adjustable parameters. The crystal field parameters applied in the calculation are evaluated by the superposition model, which leads the defect structure of Cr3+ center in CGGG: Cr3+ crystal to be determined. The outcomes are discussed.

Reflectance variation in boreal landscape during the snow melting period using airborne imaging spectroscopy

We aim a better understanding of the effect of spring-time snow melt on the remotely sensed scene reflectance by using an extensive amount of optical spectral data obtained from an airborne hyperspectral campaign in Northern Finland. We investigate the behaviour of thin snow reflectance for different land cover types, such as open areas, boreal forests and treeless fells. Our results not only confirm the generally known fact that the reflectance of a melting thin snow layer is considerably lower than that of a thick snow layer, but we also present analyses of the reflectance variation over different land covers and in boreal forests as a function of canopy coverage. According to common knowledge, the highly variating reflectance spectra of partially transparent, most likely also contaminated thin snow pack weakens the performance of snow detection algorithms, in particular in the mapping of Fractional Snow Cover (FSC) during the end of the melting period. The obtained results directly support further development of the SCAmod algorithm for FSC retrieval, and can be likewise applied to develop other algorithms for optical satellite data (e.g. spectral unmixing methods), and to perform accuracy assessments for snow detection algorithms.A useful part of this work is the investigation of the competence of Normalized Difference Snow Index (NDSI) in snow detection in late spring, since it is widely used in snow mapping. We conclude, based on the spectral data analysis, that the NDSI -based snow mapping is more accurate in open areas than in forests. However, at the very end of the snow melting period the behavior of the NDSI becomes more unstable and unpredictable in non-forests with shallow snow, increasing the inaccuracy also in non-forested areas. For instance in peatbogs covered by melting snow layer (snow depth < 30 cm) the mean NDSI -0.6 was observed, having coefficient of variation as high as 70%, whereas for deeper snow packs the mean NDSI shows positive values.

Investigations of the optical and EPR spectral data for the trigonal Cr3+ center in ZnGa2O4: Cr3+ crystal with a unified method-complete diagonalization of energy matrix

The optical and EPR spectral data of the trigonal Cr3+ centers in ZnGa2O4: Cr3+ crystal are unifiedly calculated by applying the complete diagonalization of energy matrix method resting on the two-spin-orbit-parameter model, where the one-electron basis functions are the molecular orbitals and the contributions from both the spin-orbit parameters of dn ion and ligand ion are included. Thus, the Racah parameters B, C, two spin-orbit parameters and two orbit reduction factors can be evaluated from a adjustable parameter, the covalence factor, and so only three adjustable parameters are used in the calculation. The ten calculated spectral data (seven optical band positions and three EPR parameters, g factors g//, g⊥ and zero-field splitting D) are rationally consistent with the experimental values. The defect structure of the trigonal Cr3+ center is also given. These outcomes are discussed.

Influence of Co-Dopant on Structural, Optical and Electrochemical Properties of Zinc Sulphide Quantum Dots

In the present work, solution based simple chemical precipitation method has been employed to prepare undoped, cobalt (Co)-doped and cobalt, nickel (Co, Ni) co-doped ZnS quantum dots (QDs). The XRD pattern revealed that all samples displayed cubic zinc blende structure. The average crystallite size of as prepared ZnS QDs were found to be in 1.0 to 1.4 nm range. Surface morphological of synthesized samples were recorded and some distinction in morphological features between undoped, doped and co-doped ZnS QDs were noticed. EDX analysis confirms the presence of all corresponding elements in the samples. The blue-shift in the absorption spectra was observed. The optical band gap energy (Eg) for all the hybrid ZnS QDs samples were evaluated by using UV-Visible optical absorption spectral data. In PL analysis, emission band at 660 nm was found to be quenched as ZnS QDs interact with dopant and co-dopant. Electrochemical analysis was carried out by transition of photogenerated electrons in undoped, cobalt (Co)-doped and cobalt, nickel (Co, Ni) co-doped ZnS QDs modified glassy carbon electrodes. To authenticate the results of PL and electrochemical studies, photocatalytic behaviour of QDs were studied and positive impact of doping and co-doping process on photo degradation were noticed and discussed.

Advanced catalytic performance of amorphous MoS2 for degradation/reduction of organic pollutants in both individual and simultaneous fashion

A cluster [(S2)2Mo(S2)2Mo(S2)2], has been used to synthesise molybdenum sulfide microparticles (MPs) by solvothermal treatments under inert environment. During synthesis, surfactants i.e. oleylamine and dodecanthiol take part in chief role in shaping the morphology of MPs into ultrathin nano-fibre, and nano-rod. MPs have been characterized by X-ray diffraction analysis, energy dispersive X-ray spectroscopy, transmission electron microscopy and UV−vis spectroscopic techniques. The optical spectral data reveals a simultaneous presence of direct and indirect band gap in both MoS2. The material emerges as an effective catalyst towards the mineralization of different cationic dyes (rhodamine B and methylene blue) and anionic dye (rosebngal). These MPs have also been effectively used for the simultaneous degradations of different dyes in the same reaction mixture which make further highlighted the catalytic performances of MoS2. The above kinetics of the decomposition processes were examined and found to follow the pseudo-first-order reaction model. The plausible mechanism has been explained by comparing the position of conduction band levels of MoS2 (measured by Mott-schotky and touc's plot) and potential value of borohydride. We have also investigated the active species behind the degradation of dyes by using different scavengers. The new catalyst was also effective for the degradation of mixture of dyes to the same extent as it was in case of individual.

Synthesis and optimization of Novel Chitosan/Cellulose Acetate Natural Polymer Membrane for water treatment

Chitosan (Ch) and Cellulose Acetate (CA) natural polymer in addition to other samples with different mass fractions of Chitosan/Cellulose Acetate (Ch/CA) were synthesized via simple casting route. Prepared samples were studied using FT-IR and UV/vis spectroscopic techniques. Structural variations due to the process of blending were retraced using X-ray diffraction data (XRD) and morphological investigation using scanning electron microscopy (SEM). Obtained spectral data reveals compatibility and complexation between polymer constituents identified through presence of polymer characteristic peaks with small variation in both intensity and position along with change in the value of optical energy gap from UV optical absorption spectral data. XRD pattern indicate the semicrystalline nature of the studied sample with an observable change in the crystallinity. Moreover, scanning electron microscopic (SEM) micrographs reveals homogenous structure without any evidence for agglomerations nearly in all compositions.

Unified research of the EPR and optical spectral data for Cr3+-doped Lu3Al5O12 crystal

In this article, we apply a complete diagonalization (of energy matrix) method to simultaneously calculate the spin-Hamiltonian (or EPR) parameters (g factors g//, g⊥ and zero-field splitting D) and optical band positions (or crystal field energy levels) of Cr3+-doped Lu3Al5O12 (LuAG) crystal. The method is based on the two-spin-orbit-parameter model where besides the effects of spin-orbit parameter of central dn ion in the common crystal-field theory, those of ligand ions are contained. The calculated results indicate that by using only three adjustable parameters, the eight observed spectroscopic data (three EPR data and five optical bands) are reasonably explained. This suggests that this diagonalization method is effective and applicable in the unified calculation of EPR and optical spectral data for d3 ions in crystals. The local lattice distortion caused by the Cr3+ impurity in LuAG crystal is also estimated. The outcomes are discussed.