IR Reflection Research Articles

Optical signatures of the chiral anomaly in mirror-symmetric Weyl semimetals

The chiral anomaly is a phenomenon characteristic of Weyl fermions, which has condensed matter realizations in Weyl semimetals. Efforts to observe smoking gun signatures of the chiral anomaly in Weyl semimetals have mostly focused on a negative longitudinal magnetoresistance in electronic transport. Unfortunately, disentangling the chiral anomaly contribution in transport or optical measurements has proven non-trivial. Recent works have proposed an alternative approach of probing pseudoscalar phonon dynamics for signatures of the chiral anomaly in non-mirror-symmetric crystals. Here, we show that such phonon signatures can be extended to scalar phonon modes and mirror-symmetric crystals, broadening the pool of candidate materials. We show that the presence of the background magnetic field can break mirror symmetry strongly enough to yield observable signatures of the chiral anomaly even in mirror-symmetric materials. Specifically for mirror-symmetric Weyl semimetals such as TaAs and NbAs, including the Zeeman interaction at $B \approx 10$T, we predict an IR reflectivity peak will develop with an $\mathbf{E}_\text{IR}\cdot\mathbf{B}$ dependence.

Zr- and La-containing Catalysts in Synthesis of Methanol and Dimethyl Ether

Zirconium oxide samples synthesized and modified with Al, Si, W oxides were studied as dehydrating components of bifunctional catalysts for synthesis of dimethyl ether. ZrO2 modified with Al and Si oxides is inactive in the dehydration of methanol, but its dehydrating activity becomes comparable with the activity of γ-Al2O3 upon introduction of WO3. According to the data on methanol adsorption at 46°C, the adsorption capacity of ZrO2 modified with SiO2 is comparable with the capacity of γ-Al2O3, and that of ZrO2 modified with WO3 is four times lower. The difference in the catalytic and adsorption behavior of the samples is accounted for by the data of in situ high-temperature diffuse reflection IR spectroscopy. A high content of weak Bronsted acid centers is observed on the ZrO2 surface, with the interaction of these with methanol resulting in the methoxylation of the catalyst surface. When W oxide is deposited onto zirconium oxide, the surface has strong Bronsted centers involved in the reaction of methanol dehydration. A coprecipitation from solution of nitrate salts of Cu, Zn, La with Na carbonate, followed by the procedures of filtration, washing, and thermal treatment, yielded a catalyst for synthesis of methanol, the activity of which is close to that of the industrial catalyst.

Lattice Dynamics and Electronic Properties of a BaGa2GeS6 Nonlinear Crystal: Raman Scattering, IR Reflection, and ab initio Calculations

We have measured the polarized Raman scattering and IR reflection spectra of a BaGa2GeS6 crystal, the Ga and Ge atoms of which are disordered, randomly occupying crystallographic positions of the same kind. The IR reflection spectra have been processed by the dispersion analysis method. The dispersion of phonons, the density of phonon states, the electronic band structure, and the partial densities of electronic states have been calculated in the DFT approximation using the alchemical potential method for disordered Ga and Ge atoms. It has been found that the stretching vibrations in the vibrational spectra are separated from the bending modes by a gap of about 100 cm–1 and that the band structure of the crystal has an indirect energy gap.

Data fusion of GC-IMS data and FT-MIR spectra for the authentication of olive oils and honeys-is it worth to go the extra mile?

The potential benefit of data fusion based on different complementary analytical techniques was investigated for two different classification tasks in the field of foodstuff authentication. Sixty-four honey samples from three different botanical origins and 53 extra virgin olive oil samples from three different geographical areas were analyzed by attenuated total reflection IR spectroscopy (ATR/FT-IR) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). The obtained datasets were combined in a low-level data fusion approach with a subsequent multivariate classification by principal component analysis-linear discriminant analysis (PCA-LDA) or partial least squares-discriminant analysis (PLS-DA). Performing a back projection of PCA loadings, the influence of variables in the FT-IR spectra (one-dimensional) and the GC-IMS profiles (two-dimensional) on the discrimination was visualized within the original axis of the two data sources. Validation results of the classification models were compared to the results that could be obtained by using the individual data blocks separately. For both the honey and olive oil samples, a decreased cross-validation error rate and more robust model was obtained due to the low-level data fusion. The results show that data fusion is an effective strategy for improving the classification performance, particularly for challenging classification tasks such as the discrimination of olive oils with different geographical origin. Graphical abstract.

Chemical and Physical Effects of Fluoride on the Corrosion of Austenitic Stainless Steel in Polluted Phosphoric Acid

The effect of fluoride ions was investigated on the austenitic stainless steel in a typical solution of phosphoric acid that is used in industrial process, for clear understanding the damage that caused by corrosion to special alloying material Uranus B6 at temperature of 80 °C. For that the electrochemical and spectroscopy methods were used like potentiodynamic and electrochemical impedance spectroscopy, X-ray diffraction and UV–visible–IR reflection, Scanning electron microscopy and energy-dispersive spectroscopy analysis (SEM–EDX). The electrochemical methods show the drastic effect of fluoride on the passivation parameters, especially icrit, ipass and Epit caused by decreasing the alloy elements in the surface alloy, specially the molybdenum. Moreover, the spectroscopy results reflect that fluoride has two axes of interaction with the surface alloy; chemical interaction that was appeared by the dissolution mechanism, which it increases the dissolution of the base alloy atom and the alloying elements and this result was improved by the UV–visible–IR and EDX analysis. And the physical effect was demonstrated by X-ray diffraction, which is showing a deformation of the crystalline structure of surface alloy; and different pit types were detected by SEM. And the suggestion of the effect of fluoride on the nickel percent in the passive film and also on the molybdenum and copper has been proposed as a mechanism to explain these results.

Optical and Electrical Properties of Tb–ZnO/SiO2 Structure in the Infrared Spectral Interval

Optical and electrophysical properties of terbium-doped zinc oxide films have been studied, by using the external reflection IR spectroscopy. The films were deposited onto silicon oxide substrates with the help of the magnetron sputtering method. A theoretical analysis of the reflection spectra of the ZnO/SiO2 structure is carried out in the framework of a multioscillatory model in the spectral interval 50–1500 cm−1 and for the electrical field orientation perpendicular to the c-axis (E⊥C). The method of dispersion analysis is applied to determine the optical and electrical properties of ZnO films, as well as the oscillator strengths and damping coefficients in the ZnO film and the SiO2 substrate. The influences of the phonon and plasmon-phonon subsystems in the ZnO film on the shape of IR reflection spectra registered from the Tb–ZnO/SiO2 structure are elucidated.

Structure and Lattice Dynamics of Nd2TiO5 and Sm2TiO5 Crystals: Ab Initio Calculation

Ab initio study of the crystalline structure and the phonon spectrum of R2TiO5 (R = Nd, Sm) crystals is conducted using the density functional theory. The calculations are carried out using the hybrid functional, which takes into account the contribution of nonlocal exchange to the Hartree–Fock formalism. Coordinates of ions in the unit cell and lattice constants, as well as frequencies and types of fundamental vibrations, intensities of lines of Raman and IR reflectance spectra are determined. The elastic constants of R2TiO5 are calculated for the first time.

SiO2 coated platy TiO2 designed for noble UV/IR-shielding materials

SiO2 coated platy TiO2 (S-pTi) was prepared as a noble UV/IR(Ultraviolet/Infrared)-shielding material by a modified Stöber method. S-pTi consists of a dense and uniform SiO2 shell onto platy TiO2 (pTi) core, and the thickness of SiO2 shell layer was coated about 8–20 nm by tuning SiO2 coating amount. The zeta-potential of S-pTi was decreased from −12 to −32 mV with increasing amounts of coated SiO2, indicating the improvement of dispersibility between the particles. The UV-shielding ability of S-pTi was improved by enhancing UV absorption of the SiO2 coating layer onto pTi and thus the photocatalytic activity was suppressed effectively. Compared to nanosized TiO2(nTi), S-pTi showed higher UV absorption at the shorter wavelength and exhibited higher IR reflectance because of high reflective index and the crystal shape and size of pTi to reflect the IR effectively under its wide shielding area. These results can contribute to the prevention of harmful UV and the maintenance of a cool environment from IR heat source as noble UV/IR-shielding materials on the skin.

CO2–H2O solubility in K-rich phonolitic and leucititic melts

The solubility of CO2 and H2O in phonolitic and leucititic melts from Vesuvius and Colli Albani was investigated experimentally at 1250 °C and pressures between 50 and 300 MPa as a function of CO2–H2O fluid composition. Quenched glasses were analyzed for their volatile contents by thermogravimetry, carbon–sulfur analysis, and Fourier transform infrared (FTIR) spectroscopy, which enabled the determination of the absorption coefficients of the H2O- and CO2-related IR bands at 5200 cm−1 (H2O molecules), 4500 cm−1 (OH groups), and the carbonate doublet at 1510 and 1430 cm−1. No molecular CO2 was detected in our phonolitic and leucititic glasses. Leucititic glasses with elevated CO2 concentrations (approaching total absorption in transmission FTIR measurements) were also analyzed quantitatively by micro-ATR (attenuated total reflection) IR spectroscopy. While the water solubility in both melts is quite similar for pure H2O as well as for mixed CO2–H2O fluids (at given $$ f_{{{\text{H}}_{ 2} {\text{O}}}} $$ ), the CO2 solubility depends strongly on melt composition. In the range of 100–300 MPa, the solubility of pure CO2 increases from 580 to 1800 ppm in the phonolite melt and from 2950 to 8460 ppm in the leucitite melt. For the leucitite melt, we observe a single power law trend of CO2 solubility as function of $$ f_{{{\text{CO}}_{ 2} }} $$ , regardless if the melt was equilibrated with pure CO2 or mixed CO2–H2O fluids, indicating that water acts as diluent of the fluid phase. However, for the phonolite melt, we observe for mixed CO2–H2O samples a positive solubility deviation from the power law trend defined by the data for pure CO2 solubility. This effect seems to increase with increasing water content and pressure. Our interpretation is that this enhanced CO2 solubility is caused by melt depolymerization induced by water and is more apparent in the relatively polymerized phonolitic melt compared to the relatively depolymerized leucititic melt.

Further explore on the behaviors of IR electrochromism of a double layer constructed by proton acid-doped polyaniline film and ITO layer

In this study, the IR electrochromic films were constructed by dodecylbenzene sulfonate acid (DBSA)-doped polyaniline (PANI) film and an indium tin oxide glass (ITO). We used the in situ electrochemical deposition method for preparing the DBSA-doped PANI. The IR electrochromic properties of the double layer structure have been investigated minutely. We discovered two operation modes of modulation IR emissivity of the double layer structure with the increase of thickness of the PANI layer. When the thickness of the PANI film was within a certain range, its switching between leucoemeraldine (LB) and emeraldine salt (ES) modulated IR transmittance of the PANI film to realize regulation of the IR emissivity of the double layer structure (Mode Ⅰ). When the thickness of the PANI film reached a certain value, its IR transmittance was lower, the IR emissivity modulation of the double layer structure was determined mainly by the IR reflectance of the PANI film which depended on the pseudo-metallic behavior of the PANI film (Mode Ⅱ).

Practical application of visible-induced luminescence and use of parasitic IR reflectance as relative spatial reference in Egyptian artifacts

Egyptian blue (CaCuSi4O10) is one of the most ancient artificial pigments, widely used in ancient times. Its peculiarity is an exceptional infrared emission upon visible excitation, allowing an easy and non-invasive diagnostic through the so-called visible-induced luminescence (VIL) technique. Usually, it requires total absence of infrared parasitic light, highlighting areas in which the pigment is present even in traces. In this report, we propose the introduction of a small portion of IR parasitic light as spatial reference for locating Egyptian blue on analyzed object. In VIL modality, the contemporary reflectance transformation imaging (RTI) and 3D photogrammetric model reconstruction were performed with the final 3D rebuilding of surface, morphology, and pigment distribution. We demonstrated the possibility to perform VIL and 3D photogrammetry without opening the conservation case that is extremely important by a conservation point of view, avoiding any microclimatic alteration, compatibly with the minimum invasiveness (absence of contact and displacement of the object).

A flexible cell for in situ combined XAS-DRIFTS-MS experiments.

A new cell for in situ combined X-ray absorption, diffuse reflectance IR Fourier transform and mass spectroscopies (XAS-DRIFTS-MS) is presented. The cell stands out among others for its achievements and flexibility. It is possible to perform XAS measurements in transmission or fluorescence modes, and the cell is compatible with external devices like UV-light and Raman probes. It includes different sample holders compatible with the different XAS detection modes, different sample forms (free powder or self-supporting pellet) and different sample loading/total absorption. Additionally, it has a small dead volume and can operate over a wide range of temperature (up to 600°C) and pressure (up to 5 bar). Three research examples will be shown to illustrate the versatility of the cell. This cell covers a wider range of applications than any other cell currently known for this type of study.

Analysis of the polarized IR reflectance spectra of the monoclinic α-oxalic acid dihydrate.

In contrast to the extensive molecular and crystal structure investigations on oxalic acid dihydrate (C2H2O4·2H2O, α-POX) and its deuterated analogues (α-DOX), stands the absence of a complete vibrational spectra analysis. Such analysis is desirable in view of the proton dynamics in α-POX crystals. In this communication we report the room temperature polarized IR reflectance spectra of a single crystal of α-POX recorded from the ac crystal plane, and from the plane containing the b-crystallographic axis, with polarization along the axis. Dispersion analysis of the reflectance spectra of both Bu and Au symmetry type modes, using model dielectric and reflectance function valid for the monoclinic case, have been performed and the results are discussed. Some aspects of the obtained fit results for some of the spectral regions and the peculiar change of the reflectance function with polarization angle are also discussed in this work. A correlation between the crystal structure and measured spectra, together with the results of the performed dispersion analysis, gave answers to some of the problems concerned with the orientation of the transition dipole moments of the IR active modes. The assignment of modes is assisted by DFT calculations. Another aspect covered in this work is the model reflectance functions using different averaging theories that have been applied in obtaining the reflectance spectrum of a polycrystalline sample. The results of the comparison between these spectra and the recorded reflectance spectra from a polycrystalline sample were further discussed.

Fabrication of Nanopillar Crystalline ITO Thin Films with High Transmittance and IR Reflectance by RF Magnetron Sputtering.

Nanopillar crystalline indium tin oxide (ITO) thin films were deposited on soda-lime glass substrates by radio frequency (RF) magnetron sputtering under the power levels of 100 W, 150 W, 200 W and 250 W. The preparation process of thin films is divided into two steps, firstly, sputtering a very thin and granular crystalline film at the bottom, and then sputtering a nanopillar crystalline film above the bottom film. The structure, morphology, optical and electrical properties of the nanopillar crystalline ITO thin films were investigated. From X-ray diffraction (XRD) analysis, the nanopillar crystalline thin films shows (400) preferred orientation. Due to the effect of the bottom granular grains, the crystallinity of the nanopillar crystals on the upper layer was greatly improved. The nanopillar crystalline ITO thin films exhibited excellent electrical properties, enhanced visible light transmittance and a highly infrared reflectivity in the mid-infrared region. It is noted that the thin film deposited at 200 W showed the best combination of optical and electrical performance, with resistivity of 1.44 × 10−4 Ω cm, average transmittance of 88.49% (with a film thickness of 1031 nm) and IR reflectivity reaching 89.18%.

Surface reaction kinetics of room temperature atomic layer deposition of ZnO observed by in situ IR absorption spectroscopy

Room temperature (RT) atomic layer deposition (ALD) of ZnO is developed by using a precursor of dimethyl zinc (DMZ) and plasma excited humidified argon. Surface reactions of RT ALD of ZnO are investigated by an in situ observation of multiple internal reflection IR absorption spectroscopy. The saturation condition of DMZ and plasma excited humidified argon is discussed by the IR absorbance spectra measured from the sample surface. In the ALD experiment, the grown film is identified as the fully oxidized ZnO by x-ray photoelectron spectroscopy. The growth per cycle is measured to be 0.046 nm/cycle. In this paper, the authors will discuss the mechanism of surface reaction in the ALD process.

Study on Ti content in Low thermal expansion silica glass based on IR reflectance spectra

Ultra-Low thermal expansion (ULE) silica glass with essentially zero coefficient of thermal expansion is one of the most promising achievements in glass technology in a few decades. The property of the low thermal expansion coefficient makes it a suitable candidate for optical systems to be used in critical environments like space or vacuum. In this paper, by the help of ICP-OES and Infrared reflectance spectra, we measured titanium content of different samples and its corresponding reflection spectrum. We compared the linear fitting relation of Ti content with reflectivity and of Ti content with integration area of Gaussian fitting peak with a weighted average wave centre in 923cm-1. Results show that the latter one has a better correlation coefficient. By the tests of the IR reflectance spectrum of samples, we can deduce the Ti content using the linear fitting result.

Investigation of undoped and Tb-doped ZnO films on Al2O3 substrate by infrared reflection method

Undoped and Tb-doped ZnO thin polycrystalline films grown on Al2O3 substrate by magnetron sputtering approach were investigated using external infrared reflection in the spectral range from 50 to 5000 cm−1. The modelling of the IR reflection spectra was performed for absorbing film on semi-infinite substrate. For undoped ZnO film, the single oscillator model was used. Theoretical calculations were found to be in good agreement with the experimental results. The free carrier concentration, mobility and specific conductivity of electrons in ZnO films on Al2O3 substrates with E→⊥c→ orientation were determined. It was found that sheet resistance of the films investigated was much higher than that obtained from IR reflection spectra, which was ascribed to the presence of high resistive spaces between ZnO columns. In this case, IR reflection method is suitable for analysing the electrical parameters of textured materials when planar conductivity gives the incorrect results. Apparent effect of Tb doping on ZnO conductivity was not observed in the films investigated.

Enhancing the signal strength of surface sensitive 2D IR spectroscopy.

Spectroscopic techniques that are capable of measuring surfaces and interfaces must overcome two technical challenges: one, the low coverage of molecules at the surface, and two, discerning between signals from the bulk and surface. We present surface enhanced attenuated reflection 2D infrared (SEAR 2D IR) spectroscopy, a method that combines localized surface plasmons with a reflection pump-probe geometry to achieve monolayer sensitivity. The method is demonstrated at 6 µm with the amide I band of a model peptide, a cysteine terminated α-helical peptide tethered to a gold surface. Using SEAR 2D IR spectroscopy, the signal from this sample is enhanced 20 000-times over a monolayer on a dielectric surface. Like attenuated total reflection IR spectroscopy, SEAR 2D IR spectroscopy can be applied to strongly absorbing solvents. We demonstrated this capability by solvating a peptide monolayer with H2O, which cannot normally be used when measuring the amide I band. SEAR 2D IR spectroscopy will be advantageous for studying chemical reactions at electrochemical surfaces, interfacial charge transfer in photovoltaics, and structural changes of transmembrane proteins in lipid membranes.

Optically Transparent Polymer Coating Embedded with IR Reflective Rare Earth Yellow Pigment: - Innovative Strategy for Cool Windows

The increasing atmospheric temperature due to global warming demands development of coatings for glass windows that permits the light but not the heat. It is documented that the absorption of infrared radiations [IR] in the solar spectrum is the cause of heat build-up. Technologically it’s a challenge to have optical transparency and IR reflectance combined in a single-coat for any heat control cool-windows. Polymer coatings embedded with IR reflective ceramic dispersoids offer these stringent requirements, i.e light penetration and heat reflection when the glass panels are exposed to direct sun light. This current study focused on this concept. Here IR reflective rare earth colorant was first prepared and subsequently embedded in polymer resin to develop heat management coatings. The characteristic properties of the pigment as well as the coating were analyzed and were found that the inorganic dispersoids enhance the IR reflectance quality of polymer coats from 10% to 40%. The surface morphology, crystallinity and particle size of the product were also investigated. The inorganic-polymer composite coat offers thermal stability, light fastness and photo-physical properties

Динамика решетки и электронные свойства нелинейного кристалла BaGa-=SUB=-2-=/SUB=-GeS-=SUB=-6-=/SUB=-: комбинационное рассеяние, ИК отражение и расчет ab initio

AbstractWe have measured the polarized Raman scattering and IR reflection spectra of a BaGa_2GeS_6 crystal, the Ga and Ge atoms of which are disordered, randomly occupying crystallographic positions of the same kind. The IR reflection spectra have been processed by the dispersion analysis method. The dispersion of phonons, the density of phonon states, the electronic band structure, and the partial densities of electronic states have been calculated in the DFT approximation using the alchemical potential method for disordered Ga and Ge atoms. It has been found that the stretching vibrations in the vibrational spectra are separated from the bending modes by a gap of about 100 cm^–1 and that the band structure of the crystal has an indirect energy gap.