Integrated Absorption Coefficient Research Articles

Extinction spectra in the fundamental region of hexafluoroethane at different condensed phases

RAIR spectra of liquid and crystalline hexafluoroethane were recorded in the temperature range 100–200 K. The ν5 and ν10 reflection bands had been normalized and used to obtain their extinction profiles. New normalizing method outlined in this paper. The integral absorption coefficients had been determined at each phase and compared with literature data. The contours obtained have asymmetrical and broad profiles with enhanced low frequency branch (TO-branch). The structures of these contours were explained in framework of resonance dipole-dipole (RDD) interaction. The mathematical apparatus of spectral moments were used to describe profiles of the bands studied.

Absorption of light by a particulate monolayer: Effect of ordering, concentration, and size of particles

Absorption of light by a free standing monolayer of monodisperse crystalline silicon (c-Si) spherical particles is investigated using the quasicrystalline approximation (QCA) of the theory of multiple scattering of waves. The simulation results for the partially ordered monolayer and the highly ordered monolayer with imperfect triangular lattice are presented in the ranges of particle diameters from 0.05 µm to 1 µm, monolayer filling factors from 0.1 to 0.7, and wavelengths of incident light from 0.3 µm to 1.12 µm. The spatial pattern of a monolayer affects the absorption coefficient most strongly when the particle sizes are comparable with the wavelength. The spatial-order-induced peaks in the absorption spectra of a highly ordered monolayer are studied. The spectral absorption by such a monolayer can be more than 30 times greater than that of the partially ordered monolayer in the narrow wavelength intervals. The integrated over the terrestrial solar spectral irradiance “Global tilt” ASTM G173-03 absorption coefficient is analyzed. In the wavelength range of 0.3 µm ≤ λ ≤ 1.12 µm the integral absorption can be almost twice as large as that for the partially ordered monolayer. In the wavelength range of small absorption index of c-Si (0.8 µm ≤ λ ≤ 1.12 µm) the integral absorption coefficient of highly ordered monolayer can be more than 10 times greater than for the partially ordered monolayer.

Radiation Resistance of Nanomodified Organosilicic Enamel

The paper studies the absorption spectrum and the integrated absorption coefficient of organosilicic KO-859 enamel samples modified by silicon dioxide nanoparticles and exposed to solar radiation. It is shown that nanomodification improves the radiation resistance of thermal control coatings and provides stability of their optical properties.

Formation and impact of soil particles on flame radiation in the cylinder of diesel while working on gas-motor fuel

The article deals with the formation of soot particles in the cylinder of a high-speed diesel engine with turbocharging when operating on gas engine fuel (compressed natural gas). It is shown that the main source of data on the processes occurring in the engine cylinder is the indicator diagram. But the data obtained with its help is often not enough to answer a number of questions regarding the characteristics of the course of intra-cylinder processes. As an example, one can cite the problem of studying the formation of harmful substances in an engine cylinder during fuel combustion, such as soot (C), the mechanism of the chemical kinetics of the formation of which has not yet been explicitly solved. The article presents the spectral effective cross-sections of the absorption of soot particles, depending on the optical properties and dispersion, spectral and integral absorption coefficients of soot particles, depending on the angle of rotation of the crankshaft.

Radiation stability of silicon-organic varnish modified with nanoparticles

An effect of SiO2 nanoparticles modification on spectra and integral absorption coefficient of silicon-organic varnish KO-859 before and after 30 keV electron and 100 keV proton exposure has been investigated. An increase in reflectance in UV, visible, and near-IR ranges and radiation stability of varnish modified with nanoparticles in comparison to unmodified have been established.

Temperature dependences of hydrous species in feldspars

Feldspars are abundant in the crust of the Earth. Multiple hydrogen species such as OH, H2O and NH4+ can occur in the structure of feldspars. Hydrogen species play a critical role in influencing some properties of the host feldspars and the crust, including mechanical strength, electrical property of the crust, and evolution of the crustal fluids. Knowledge of hydrous species in feldspars to date has been mostly derived from spectroscopic studies at ambient temperature. However, the speciation and sites of hydrous species at high temperatures may not be quenchable. Here, we investigated the temperature dependences of several typical hydrous components (e.g., type IIa OH, type IIb OH and type I H2O) in feldspars by measuring the in situ FTIR spectra at elevated temperatures up to 800 °C. We found that the hydrous species demonstrated different behaviors at elevated temperatures. With increasing temperature, type IIa OH redistributes on the various sites in the anorthoclase structure. Additionally, O–H vibration frequencies increase for types IIa and IIb OH, and they decrease for type I H2O with increasing temperature. In contrast to type I H2O which drastically dehydrates during the heating process, types IIa and IIb OH show negligible loss; however, the bulk integral absorption coefficients drastically decrease with increasing temperature. These results may have implications in understanding the properties of hydrous species and feldspars at non-ambient temperatures, not only under geologic conditions but also at cold planetary surface conditions.

MOLECULAR ABSORPTION SPECTROSCOPY IN THE UV-VIS REGION FOR THE QUINOLINE-N-OXIDE, NICOTINAMIDE-N-OXIDE AND 2,2-DITHIOBISPYRIDINE-N-OXIDE LIGANDS

The purpose of this study was to analyze and quantify spectral parameters, the absorption bands, specifically in the uv-visible region of some N-oxide ligands. From the spectra, the area under the absorption band, the molar absorptivity, the integrated absorption coefficient and the oscillator strength by the Gaussian approximation method were calculated for each of them, using the proposed evaluation by Drago and Figgs. According to the obtained results, it can be concluded that the heterocyclic compounds studied absorb very well electromagnetic radiation in the ultraviolet region. For the ligands QUI-NO and NIC-NO it was observed that there are two types of bands, primary and secondary, being transitions of type π → π * and n → π*, respectively. For DITBIS-NO, there was only one primary band (transition 1) and two additional shoulders, which had the highest observed absorbance coefficient. These ligands are expected as potential electron donors in complex systems whose purpose is to change the energy levels of the electronic system in order to promote a better utilization of the absorbed energy and therefore a better efficiency.

The Influence of Technological Regimes of Synthesizing a Solar Furnace on the Phase Composition of TiO2-CuO Cermets and the Optical Properties of Coatings on Their Basis

We present the results of studying the effect of technological synthesis regimes of a solar furnace using the method of a partial metal reduction of one of the oxides on the phase formation of cermet composite materials of the TiO2-CuO system. It has been established that the phase composition of the synthesized cermet composite materials depends on the carbon concentration, melting temperature and cooling rate. The dependence of the spectral-optical properties of selectively absorbing coatings on the production technology and properties of synthesized composite materials has been presented. It has been found that the coatings fabricated by melting in air with overheating at a melt cooling rate of about 105–106°C/s have the highest values of the integral absorption coefficient, α s = 91.0–94.5%.

Line-by-line spectroscopic parameters of HFC-32 ro-vibrational transitions within the atmospheric window around 8.2 μm

Difluoromethane (CH2F2,HFC-32) presents strong ro-vibrational bands within the 8–12 μm atmospheric window and hence it represents a greenhouse gas able of contributing to global warming. Numerous spectroscopic studies have been devoted to this molecule, however, much information on line-by-line parameters, like line intensities and broadening parameters, is still lacking. In this work, line-by-line spectroscopic parameters are retrieved for several CH2F2 ro-vibrational transitions belonging to the ν7 band located around 8.5 μm. Self-broadening as well N2– and O2– broadening experiments are carried out at room temperature by using a tunable diode laser (TDL) spectrometer. The line shape analysis of CH2F2 self-broadened spectra leads to the determination of resonant frequencies, integrated absorption coefficients and self-broadening parameters, while CH2F2–N2 and CH2F2–O2 broadening coefficients are obtained from foreign-broadening measurements. In addition, the broadening parameters of CH2F2 in air are derived from the N2– and O2– broadening coefficients. The results of the present work provide fundamental information to measure the concentration profiles of this molecule in the atmosphere through remote sensing spectroscopic techniques.

Temperature dependence of collisional induced absorption (CIA) bands of CO2 with implications for Venus’ atmosphere

The intensity and temperature dependence of four CO2 collision induced absorption (CIA) bands in two spectral regions, 1100–1600 cm−1 and 2500–3200 cm−1 have been investigated. The measurements have been performed with a Fourier Transform InfraRed (FT-IR) spectrometer operating in a wide spectral range, from 350 to 25000 cm−1 (0.4 to 28.5 µm) with a spectral resolution of 2 cm−1, interfaced with a high pressure-high temperature (HP-HT) absorption cell with an optical path of about 2 cm. While the integrated band intensity of allowed bands shows a linear dependence versus density, the collision-induced integrated band intensity increases quadratically with the density, due to the absorption by pairs of molecules, which allows identifying the CIA bands unambiguously. While below 300 K the binary integrated absorption coefficients exhibit a pronounced temperature dependence due to the presence of dimers, a much weaker temperature dependence has been found above 300 K. The results are important for the radiative transfer calculations of Venus’ atmosphere. The integrated band intensities of the studied bands have been calculated for Venus’ atmosphere from 40 km down to the surface by extrapolating the binary integrated absorption coefficients to the relevant temperatures.

Optical properties of zinc tellurite glasses doped with Cu2 + ions

Copper-containing ZnO–TeO2 glasses were synthesized using orthotelluric acid, zinc nitrate and the formed batch was doped with copper nitrate. EPR and optical spectra in a wide transparency range from were measured for all glass samples. The values of the spin-Hamiltonian parameters indicate that the Cu2+ ions in the glasses are present in octahedral coordination with some trigonal distortion. The molecular orbital bonding parameters have been calculated and were found to be independent of Cu2+ concentration in glasses. The optical transmittance spectra of doped glasses show a single broad band at 820nm, which was assigned to the overlapping 2B1g→2B2g, 2B1g→2Eg and 2B1g→2A1g electronic transitions. The spectral dependence of the specific absorption coefficient of Cu2+ ions was calculated for glass samples in the range of 310–2800nm and was found that the specific absorption coefficient at 820nm is (103±1) cm−1/(wt%) and the integral absorption coefficient in the range 0.5–2.8μm is (63±2) cm−2/(ppm wt). From the optical data some optical parameters such as the optical energy gap, Urbach energy, metallization criterion and the cut-off wavelength were calculated. It is observed that the optical band gap decreases with an increase in concentration of copper content.

Optical properties of the MoO3 – TeO2 glasses doped with Ni2 +–ions

The binary MoO3 – TeO2 glasses doped with 0–0.5mol% of Ni2+ ions were prepared by the melt-quenching technique using inorganic salts and acids as starting materials. The optical transmission spectra of all prepared glasses were studied in the wavelength range 0.5–6μm. Two broad bands with maxima at 744 and 1318nm are produced by octahedrally coordination nickel ions. The crystal field splitting energy and Racah parameters of Ni2+ ions were calculated by using the Tanabe-Sugano diagrams. The spectral dependence of the specific absorption coefficient of nickel was established and the value of the integral absorption coefficient in the wavelength range 0.6–2.8μm was found as (14.5±0.3) cm−2/(ppmwt). The value of the optical band gap is observed to decrease while the refractive index and Urbach's energy increase with increase in the concentration of Ni2+ in the glasses.

English

The optical transition probabilities and hetero-association of caffeine with norfloxacin were obtained using UV-Vis spectroscopy in aqueous solution at room temperature (295K). The heter-association constant of norfloxacin-caffeine complexes (6.67×103 M-1) was obtained using Benesi-Hildebrand approach by linear curve fitting to the experimental data. In order to characterize the binding system of the compounds, the thermodynamic parameters were investigated using Vant’s Hoff equation at the temperature ranges (295 to 304K) with a change in enthalpy value (-1.277±0.103 kJ.mol-1.K-1). The values of change in the thermodynamic parameters indicated that the electrostatic forces play the major role in the binding reaction between the molecules of norfloxacin-caffeine complexes. In addition, the optical transition probabilities of norfloxacin were also calculated in the wavenumber regions from (20000 to 40000 cm-1) by using integrated absorption coefficient techniques. This study is very important for understanding the binding reaction in biological system, nature and strength of the transition, absorption spectral interpretation, and in providing stringent test of atomic and molecular structure calculations for theoretical work of the compounds. Key words: Norfloxacin, caffeine, hetero-association, optical transition, thermodynamics, UV-Vis spectroscopy.

English

The self-association, optical transition probabilities, and hetero-association with chlorogenic acid of nicotinamide were obtained from UV-Vis spectroscopy in aqueous solution at room temperature (293K). The dimerization constant of nicotinamide ( ) was obtained using dimer model by nonlinear curve fitting technique. The hetero-association constant in the system of molecules of nicotinamide with chlorogenic acid were obtained in aqueous solution using a Benesi-Hildebrand equation. In order to characterize the binding system of the dimerization reactions for the self and hetero-association of the compound, the thermodynamic parameters were investigated using Vant’s Hoff equation at the temperature range (293 to 299K). As a result, the change of enthalpy obtained for the self and hetero-association is and respectively. The values of change in the thermodynamic parameters indicated that the hydrophobic interaction and electrostatic forces subsequently plays the major role in the binding reaction between the molecules of nicotinamide and its complexes with chlorogenic acid, respectively. In addition, the optical transition probabilities of nicotinamide were also calculated in the wavenumber regions by using integrated absorption coefficient techniques. Finally, the results of this study are very important for understanding the binding reaction in biological system, nature and strength of the transition in molecular interaction, absorption spectral interpretation, and in providing stringent test of atomic and molecular structure calculations in theoretical work of the compounds. Key words: Nicotinamide, chlorogenic acid, self-association, hetero-association, optical transition probabilities, thermodynamic properties, UV-Vis spectroscopy.

Optical Response of Mixed Molybdenum Dichalcogenides for Solar Cell Applications Using the Modified Becke–Johnson Potential

Abstract Energy bands and density of states (DOS) of mixed molybdenum dichalcogenides like MoS2, MoSeS, MoSe2, MoTe2, MoTeS, and MoTe0.5S1.5 are reported for the first time using the Tran–Blaha modified Becke–Johnson potential within full potential-linearised augmented plane wave technique. From the partial DOS, a strong hybridisation between the Mo-d and chalcogen-p states is observed below the Fermi energy E F. In addition, the dielectric constants, absorption coefficients, and refractivity spectra of these compounds have also been deduced. The integrated absorption coefficients derived from the frequency-dependent absorption spectra within the energy range of 0–4.5 eV show a possibility of using molybdenum dichalcogenides, particularly MoTe0.5S1.5, in solar cell applications. Birefringence and degree of anisotropy are also discussed using the data on refractivity and imaginary components of the dielectric constant.

Solar cells based on particulate structure of active layer: Investigation of light absorption by an ordered system of spherical submicron silicon particles

Enhancement of the performance of photovoltaic cells through increasing light absorption due to optimization of an active layer is considered. The optimization consists in creation of particulate structure of active layer. The ordered monolayers and multilayers of submicron crystalline silicon (c-Si) spherical particles are examined. The quasicrystalline approximation (QCA) and the transfer matrix method (TMM) are used to calculate light absorption in the wavelength range from 0.28μm to 1.12μm. The integrated over the terrestial solar spectral irradiance “Global tilt” ASTM G173-03 absorption coefficient is calculated. In the wavelength range of small absorption index of c-Si (0.8−1.12μm) the integral absorption coefficient of monolayer can be more than 20 times higher than the one of the plane-parallel plate of the equivalent volume of material. In the overall considered range (0.28−1.12μm) the enhancement factor up to ~1.45 for individual monolayer is observed. Maximum value of the spectral absorption coefficient approaches unity for multilayers consisting of large amount of sparse monolayers of small particles. Multilayers with variable concentration and size of particles in the monolayer sequences are considered. Absorption increasing by such gradient multilayers as compared to the non-gradient ones is illustrated. The considered structures are promising for creation of high efficiency thin-film solar cells.

Pressure and temperature dependence of CO2 solubility in hydrous rhyolitic melt: implications for carbon transfer to mantle source of volcanic arcs via partial melt of subducting crustal lithologies

We conducted high pressure and temperature experiments to determine pressure and temperature dependence of CO2 solubility in natural hydrous rhyolitic melts. The goal was to constrain the limit of CO2 transfer via hydrous silicic melt derived from subducting crust at sub-arc depths. We performed two sets of experiments: (1) to determine the FTIR absorption coefficients CO2 species (CO 2 mol. and CO3 2−) for natural rhyolitic glass and (2) to constrain the effect of temperature on CO2 solubility in rhyolitic melts. The values of e and e*, linear and integrated absorption coefficients, for CO 2 mol. matched previous studies, and values for CO3 2− had not been previously calculated for rhyolitic compositions. The use of the new e values leads to lower total CO2 solubility for rhyolitic glasses compared to those obtained using e values determined from albitic compositions. Further, we assessed the uncertainty of our fluid compositions and the quench effects on carbon speciation in glasses and constrained the pressure [ΔV and ln(K 0)] and temperature (ΔH) dependence of the CO2 dissolution reactions with the updated e values. The calculated values of ΔV, ln(K 0) and ΔH were used to calculate total CO2 in rhyolitic melts as a function of pressure and temperature. Finally, our model was applied to calculate CO2 carrying capacity of rhyolitic slab melts for any given subduction zones.

Optimisation of the parameters of a pump chamber for solid-state lasers with diode pumping by the optical boiler method

A pump chamber of the optical boiler type for solid-state lasers with transverse laser diode pumping is studied theoretically and experimentally. The pump chamber parameters are optimised using the geometrical optics approximation for the pump radiation. According to calculations, the integral absorption coefficient of the active element at a wavelength of is 0.75 – 0.8 and the relative inhomogeneity of the pump radiation distribution over the active element volume is 17 % – 19 %. The developed pump chamber was used in a Nd : YAG laser. The maximum cw output power at a wavelength of was at the optical efficiency up to 19.6 %, which agrees with theoretical estimates.

CHF3 as a probe for surface basicity

FTIR spectra of adsorbed fluoroform as a test for surface basicity have been studied on a number of oxides and zeolites. CHF3 does not dissociate even on strongest basic sites, and forms H-bond with considerable stretching CH frequency lowering. With weaker basic oxygen atoms it demonstrates the blue-shifting H-bond accompanied by CH band intensity decrease and a high frequency shift of bending vibrations. Dependence of the frequency and integrated absorption coefficient of CH stretching vibration on the strength of H-bond is discussed. The problem of basicity testing can be solved by using two different probe molecules for sites of various strength. While fluoroform is good for stronger sites, weak sites can be tested by pyrrole, acetylene or its derivatives that are more sensitive, but dissociate on the most basic oxygen centers.

Light absorption by a layered structure of silicon particles as applied to the solar cells: Theoretical study

Absorption of a layered system (multilayer) consisting of monolayers of monodisperse crystalline silicon (c-Si) spherical particles is studied using the transfer matrix method. The wavelength range from 0.28µm to 1.1µm and the particle size range from 1µm to 1000µm are considered. The results for the particulate multilayer are compared with the ones for a homogeneous plane-parallel plate of the equivalent amount of silicon (equivalent plate). It is shown that at strong absorption of silicon the absorption coefficient of the plate is larger than the one of a single monolayer of particles. In the spectral range of small and middle absorption index of silicon absorption coefficient of the monolayer can exceed the one of the plate. Absorption coefficient of the system consisting of three and more monolayers exceeds the one of the equivalent plate. The integrated over the solar spectral irradiance (“Global tilt” ASTM G173-03) absorption coefficient is calculated. It is shown that the integral absorption of the particulate structure consisting of three and more monolayers of silicon particles is more than the one of the equivalent plate. Integral absorption coefficient of the four-monolayer system composed of particles with diameter of 1µm is approximately 1.7 times larger than the one of the plate. It increases with the particles size and the number of monolayers increasing. The maximum value is close to 0.9. The scheme of the possible design of solar cell based on the particulate structure of active layer is proposed. The described method can be applied for light absorption optimization in solar cells based on silicon and other materials.