Absorption Efficiency Factor Research Articles

Inversion of Near-Surface Aerosol Equivalent Complex Refractive Index Based on Aethalometer, Micro-Pulse Lidar and Portable Optical Particle Profiler

In order to investigate the equivalent complex refractive index of atmospheric aerosols near the Earth’s surface, we conducted measurements in the Hefei region from March to April 2022. These measurements utilized a micro-pulse lidar, an Aethalometer, and a Portable Optical Particle Profiler. These measurements encompassed aerosol particle size distribution as well as standard meteorological parameters including temperature, humidity, atmospheric pressure, and wind speed. Subsequently, this dataset was employed to develop an optimization algorithm for retrieving the equivalent complex refractive indices of near-surface aerosols. The methodology relies on lookup tables containing data for extinction efficiency and absorption efficiency factors. It operates on the premise of aerosol property stability within a defined time frame, utilizing measured extinction and absorption coefficients as simultaneous constraints during this period to inversely derive both the real and imaginary parts of the aerosol complex refractive index. Results from the simulation analysis reveal that the newly optimized retrieval algorithm, which relies on lookup tables, exhibits reduced sensitivity to instrument errors when compared to single-point constraint algorithms. This enhancement results in a more efficient and dependable approach for retrieving the aerosol complex refractive index. Empirical inversion and simulation studies were carried out to determine the aerosol equivalent complex refractive index in the Hefei region, utilizing measured data. This inversion process yielded an average complex refractive index of 1.48-i0.017 for aerosols in the Hefei region throughout the experimental period. Correlation analysis unveiled a positive association between the real part of the aerosol complex refractive index and the single-scattering albedo (SSA), whereas the imaginary part displayed a linear negative correlation with the SSA. The mathematical relationship between the real part and the SSA is y=0.19x+0.62, and the corresponding relationship between the imaginary part and the SSA is y=−5.3x+0.99. This research offers a novel method for the retrieval of the aerosol equivalent complex refractive index.

Effect of morphological evolution and aggregation of plasmonic core-shell nanostructures on solar thermal conversion.

Achieving high solar energy absorption based on nanofluids (NFs) needs further study in solar photothermal conversion technology. In this work, we performed COMSOL simulations to investigate the solar energy absorption using a core-shell nanostructure composed of the Au core and shell with different materials. The influence of the radius of the Au core, the materials of the shell, and the shell thickness on the solar absorption efficiency factor (SAEF) are systematically studied. The results show that the SAEF of the Au@Li nanoparticle with ratio of 0.5 has the highest SAEF of 1.4779, increasing 1.99 times compared to that of the bare Au nanoparticle of 0.74326 with the same radius. Moreover, the optical properties, electric field distribution, and SAEF of the Au@Li dimer are further evaluated to demonstrate the aggregation effects on SAEF. We find that the SAEF of the Au@Li dimer reaches the maximum of 4.34 with a distance around 1nm, where the LSPR coupling effect in the nanogap is sharply enhanced 700 times irradiated by light with wavelength of 760nm. Finally, the direct absorber solar collector performance demonstrates that Au@Li dimer NFs can collect 93% of solar energy compared to 54% for Au@Li NFs and 51% for Au NFs. This work provides the possibility to achieve more efficient solar thermal conversion, and may have potential applications in efficient solar energy harvesting and utilization.

SOFTWARE FOR MODELING ELECTROMAGNETIC WAVE WITH THIN CONDUCTING FIBERS INTERACTION

The article is devoted to the development of software for modelling electromagnetic wave with thin conductive fibers interaction in the form of a circular cylinder. The software allows you to adjust such physical parameters as the electrical conductivity of the investigated fiber, the range of wavelengths of electromagnetic radiation, the range of fiber diameters and the complex refractive index. Software calculates the values of the efficiency factors of attenuation, scattering and absorption of the electromagnetic wave by the fiber, followed by their visualization in the form of graphs on the basis of the received data.

Interaction between thin conductive fibers and microwave radiation

We study the effect of an anomalously strong interaction of electromagnetic radiation with very thin conducting fibers. Metal, semiconductor or graphite fibers, which diameter is several hundred times smaller than the radiation wavelength, strongly absorb and scatter the electromagnetic waves, which electric vector is parallel to the fiber axis. The efficiency factors of attenuation, absorption, scattering and pressure of radiation for fibers with a diameter of several micrometers in the centimeter and millimeter ranges reach several thousand. We determine the nature of this effect. It occurs when the transverse dimension of the fiber is comparable to the thickness of the skin layer. Then the electric field of the incident wave fills the entire volume of the fiber, and the absorbed power is the highest. We also provide a theoretical analysis of such effect, determine conditions for its existence: the ratio between the radiation wavelength and the diameter of the fiber, the value of conductivity. We also provide an experimental study of the effect, when unfocused radiation beam with a wavelength of 8 mm at the output of waveguide with a \(7.2 \times 3.4\) mm cross section transfers more than 10% of the beam power to a 12 μm diameter graphite fiber. We make an analysis of the mathematical model of the process of heating of graphite fiber by a microwave radiation beam. Then we solve a heat conduction equation and find the temperature distribution along the fiber, which is in agreement with the measured one.

DEPENDENCE OF OPTICAL PROPERTIES OF TWO-LAYERED METAL-DIELECTRIC SPHERICAL NANOPARTICLES ON TEMPERATURE

The dependences of the efficiency factors of radiation absorption by spherical hybrid nanoparticles of the core-shell system, respectively, with gold-quartz and quartz-gold materials with core radii r0 = 40, 50, 60, 70 nm and shell thicknesses Δr1 = 10, 20, 30 nm in the wavelength range of 300–3000 nm at temperatures of particles and surrounding quartz T = 300, 1173 K are theoretically calculated and studied. Essential change of radiation absorption by a nanoparticle is established with an increase of temperatures of nanoparticles and environment. The change of optical properties of nanoparticles significantly influences the efficiency of energy absorption of solar or optical radiation by nanoparticles, heating temperature of nanoparticles and environment and further thermal processes. The results are interesting for purposes of creation of high-temperature solid nanostructured absorbers of solar radiation containing absorbing radiation of a nanoparticle and also for creation of new materials for high-temperature nanophotonics.

Влияние поглощения матрицы на ближнеполевые и спектральные характеристики рассеяния плазмонных сферических наночастиц

Regularities of a size dependence of extinction and absorption efficiency factors as well as of near-zone and far-zone scattering efficiency factors are studied in the spectral range of the surface plasmon resonance of absorption (SPRA) for silver spherical nanoparticles placed into absorbing matrixes with complex refraction index nm+ikappam. Numerical simulation was made with the use of the Mie theory for absorbing matrixes. Approximation of the electron mean free path limitation was used in order to take into account the intrinsic size effects into a metal nanoparticle which consist in a size dependence of its dielectric characteristics. We shown that a growth of matrix absorbency leads to a strong suppression of resonances of extinction (Qext) and near-zone scattering (QNF) efficiency factors without any essential changing of their spectral position. We established that for any fixed wavelength in the spectral range of the SPRA the values of Qext and QNF depend on metal nanoparticle sizes nonmonotonically at kappam = 0–0.1. The RNP optimal value, which corresponds to the maximal values of efficiency factors for the given material of plasmonic nanoparticles, increases at the matrix absorbency growth. The intrinsic size effects contribution to the efficiency factors resonance suppression decreases at the enhancement of nanoparticle sizes and/or matrix absorption. As an example of a real absorbing matrix with a dispersion of relraction index we considered the nickel phtalocyanine matrix (NiPc), which is interesting from the point of view of photovoltaic applications.

Influence of matrix absorbance on the near-field and spectral characteristics of plasmon spherical nanoparticles scattering

Regularities of a size dependence of extinction and absorption efficiency factors as well as of near-zone and far-zone scattering efficiency factors are studied in the spectral range of the surface plasmon resonance of absorption (SPRA) for silver spherical nanoparticles placed into absorbing matrixes with complex refraction index nm+ikappam. Numerical simulation was made with the use of the Mie theory for absorbing matrixes. Approximation of the electron mean free path limitation was used in order to take into account the intrinsic size effects into a metal nanoparticle which consist in a size dependence of its dielectric characteristics. We shown that a growth of matrix absorbency leads to a strong suppression of resonances of extinction Qext and near-zone scattering QNF efficiency factors without any essential changing of their spectral position. We established that for any fixed wavelength in the spectral range of the SPRA the values of Qext and QNF depend on metal nanoparticle sizes nonmonotonically at kappam=0-0.1. The RNP optimal value, which corresponds to the maximal values of efficiency factors for the given material of plasmonic nanoparticles, increases at the matrix absorbency growth. The intrinsic size effects contribution to the efficiency factors resonance suppression decreases at the enhancement of nanoparticle sizes and/or matrix absorption. As an example of a real absorbing matrix with a dispersion of relraction index we considered the nickel phtalocyanine matrix (NiPc), which is interesting from the point of view of photovoltaic applications. Keywords: Plasmonic naniparticles, absorbing matrixes, characteristics of near-zone and far-zone scattering.

Measurements of scattering and absorption properties of submillimeter bauxite and silica particles

Submillimeter solid particles have been considered as thermal storage media for concentrated solar power applications. Knowledge of the scattering and absorption properties of individual particles is crucial for modeling the radiative heat transfer of the particle bed. In this work, a laser scatterometer is used to measure the single-particle scattering properties at a wavelength of 635 nm by using two configurations: (1) a falling particle curtain and (2) a taped particle layer. Because a one-particle nominal thickness is formed with area fractions of 5−55% depending on the configuration, multiple scattering is minimized and hence the single scattering phase function, averaged over all illuminated particles, is directly measured. Bauxite-based ceramic particles that are strongly absorbing in the solar spectrum and silica particles that are nonabsorbing in the visible and near-infrared are investigated. The directional-hemispherical reflectance and transmittance of the taped particles are also measured to deduce the forward and backward scattering efficiency factors and the absorption efficiency factors. Only weak wavelength dependence is observed in the measured region from 380 nm to 1020 nm. The scattering phase functions of all bauxite-based particles with varying sizes and compositions are very similar and can be fitted to a Henyey−Greenstein phase function with an asymmetry factor g = −0.20. For the silica particles, forward scattering dominates and g = 0.45 yields the best fit. A Monte Carlo method is developed to model the particle scattering characteristics, and reasonable agreements between the modeling and experimental results are observed by introducing a specularity parameter.

Modeling of optical properties of plasmonic core–shell nanoparticles embedded in glass for filtering of solar radiation

The computer results of optical properties of core–shell nanoparticles embedded in glass have been presented for the selection of their parameters for effective filtering and extinction of solar infrared energy. Optical properties of TiO2-Au, Fe3O4-Au, NiO-Au, SiO2-Au particles are theoretically investigated and analyzed in the spectral interval 200–2500 nm.Core–shell SiO2-Au nanoparticles have been selected for following investigation on the base of their more appropriate optical properties in visible spectrum in comparison with others. Influence of nanoparticle parameters (radii, shell thicknesses, concentrations) on their optical properties (efficiency factors of absorption, scattering, extinction and their correlations, scattering indicatrixes, optical transmittance of nanostructured glass layer) has been investigated. It was established, that spherical SiO2-Au nanoparticles with the core radii of about 60-80 nm, shell thicknesses 5, 10 nm and concentrations ∼109-1010 cm−3 embedded in glasses can be applied for effective extinction of infrared solar radiation. The medium transmittance of nanostructured glasses with nanoparticles can be achieved 70%–80% and more in visible spectrum that is sufficient for appropriate visibility. These results can be used for the development of nanostructured energy protective glasses that prevents the penetration of infrared solar energy inside buildings or cars.

Individual efficiencies of a polycrystalline silicon PV cell versus temperature

The present paper is about an investigation on the temperature dependence of efficiencies of individual energetic process (Absorption efficiency, Thermalization efficiency, Thermodynamic efficiency and Fill factor) and overall conversion efficiencies of a polycrystalline silicon solar cell which has been investigated in temperature range 10–50 °C. All these individual efficiencies present a decrease versus the increase of the temperature. However, the thermodynamic efficiency and the fill factor are more sensitive to the temperature increase more than the absorption and thermalization efficiencies. The thermodynamic efficiency and the fill factor degradation is explained by decrease of open circuit voltage in temperature. The performance parameters as open circuit voltage, maximum power and the overall efficiencies are found to decrease with temperature while the short circuit current is observed an increase. The resistance of the semiconductor decreases with the increase of the temperature. The minoritary carriers charge acquire excessive kinetic energy which can exceed the gap energy causing an over-excitement when the temperature increase. However, this over-excitement of the minoritary carriers charge does not participate to the external current improvement.

Scattering of a non-paraxial Bessel pincer light-sheet by a dielectric sphere of arbitrary size

The scattering of a non-paraxial Bessel pincer light-sheet by a dielectric sphere of arbitrary size is studied in the framework of generalized Lorenz-Mie theory (GLMT). The electrical field of the Bessel pincer light-sheet is expanded using the vector angular spectrum decomposition method (VASDM), and its beam shape coefficients (BSCs) are derived using the method of multipole expansion and vector spherical wave functions (VSWF). By this way, the incident field, scattering field and near-surface field, and absorption and extinction efficiency factors are numerically calculated. Also, the effects of the beam order, scaling parameter, and polarization are mainly discussed. Numerical results represent that the intensity distribution of incident field, scattering field and near-surface field is intensely sensitive to the scaling parameters and the beam order. For the incident field, the bigger the order, the smaller the bending angle, and the closer the focus is to the source. By contrast, for the scattering and total field, the bigger the order, the larger the bending angle, and the farther the focus is to the source. Such results have potential applications in the imaging around steep corners and particle manipulation applications with minimal obstruction by particles.

Absorption Efficiency Assessment and Uncertainty Measurement of the Sodium Arsenite Method for Ambient NO2 Determination

The absorption efficiency and uncertainty involved in the sodium arsenite method (modified Jacobs and Hochheiser method) of NO2 measurement were studied using two standard gas concentrations (4.86 ± 0.10 µmol mol–1 (ppm) and 1.95 ± 0.10 µmol mol–1 (ppm)). An average of 71 ± 3% and 71 ± 6% absorption efficiencies, respectively were observed against reported efficiency of 82% in the published standard (IS 5182 (Part 6): 2006, BIS, 2006a) in 1-impinger system at sampling flow rate of 1 L min–1 and absorbing solution temperature of 10–15°C during gas absorption in impinger. The difference is accounted for by the variation in flow rate used in present study (1 L min–1) and that in standard method (0.2 L min–1). Uncertainty involved in the method was calculated considering a range of factors directly or indirectly affecting the measurement and was found to be 15%. Based on the comparison study performed for NO2 ambient measurements using an equivalent method (chemiluminescence continuous method) and 1-impinger system reference method, the present study highlights the importance of accurate determination of absorption efficiency factor in the NO2 pollutant measurement at laboratory level. Variations observed in the absorption efficiency and the data from inter-comparison study between manual and real-time method warranted this study to be taken up to provide solutions for improvement of the method. The use of at least three absorbers/impingers (connected in series) instead of one to obtain absorption efficiency close to unity is proposed to make the reference method independent from the use of absorption efficiency factor thus ensuring the improved data quality and comparability.

Measurement of the characteristics of protective screens for microwave radiation made of thin conductive fibers

In thin conductive fibers, which diameter is much smaller than the wavelength, under certain conditions, a very strong absorption of the microwave radiation can occur. The absorption efficiency factor can reach several thousand. It is suggested to use this effect for creation of protective screens. The absorption of radiation occurs in segments of graphite fibers with a diameter of tens micrometers (12…15 μm), which are randomly arranged on the paper or polyethylene film substrate. With such arrangement of fibers, characteristics of the screen do not depend on the radiation polarization. An advantage of the screens is also the uniformity of the frequency characteristics of transmission, absorption and reflection of radiation. The paper describes experiments on measurement of the transmission, reflection and absorption of radiation by screens in the centimeter wave range. The screens were placed in free space under different angles of the incident radiation. The measurement results were compared with the results obtained during measurements in waveguides. As it turned out, the results obtained by both methods are consistent. This makes it possible to recommend waveguide methods based on reflectometers. They are more convenient, fast and accurate than free space measurement methods.Formulas for estimating the transmission, absorption and reflection of screens are given.

Spectral Radiative Properties of a Liquid n-Octane Droplet in the Midinfrared Region

The optical constants of a liquid hydrocarbon such as liquid n-octane are basic material properties that may be used to evaluate their thermal radiation transfer capabilities. In this study, the ellipsometry method was used to measure the optical constants of liquid n-octane in the midinfrared wavelength range of 2.0–16.0 μm at temperatures of 20, 50, and 80°C. Experimental analyses indicate the significant effect of temperature on the refractive index, although it has little effect on the absorption index. With increasing temperature, the refractive index shows a linear decrease, and reduced density leads to weaker absorption intensities. The radiative properties of n-octane droplets, including the absorption and scattering efficiency factors of single droplets with droplet radii r = 10, 20, 50, and 100 μm and the absorption and scattering coefficients in a droplets-air system of droplet volume fractions fv = 2%, 3%, and 4%, were calculated using Mie theory. The numerical results indicate that, with increasing temperature, the absorption efficiency factor slightly decreases, and the variation trend of the scattering efficiency factor is more complicated. With increasing droplet radius, the absorption efficiency factor increases within the studied wavelength range, except for certain absorption peaks, but the scattering efficiency factor tends to decrease. While the absorption is greater, the scattering is weaker for a given droplet radius. With an increasing volume fraction of n-octane droplets, the absorption and scattering coefficients increase linearly within the studied wavelength range.

Scattering of a non-paraxial Bessel light-sheet by a sphere of arbitrary size

The scattering of a non-paraxial Bessel light-sheet by a sphere of arbitrary size is studied in framework of generalized Lorenz-–Mie theory (GLMT). The electrical fields of the Bessel light-sheet are expanded using the vector angular spectrum decomposition method (VASDM), and the beam shape coefficients (BSCs) of the Bessel light-sheet are derived using the method of multipole expansion and vector spherical wave functions (VSWF). The internal and near-surface fields, and absorption and extinction efficiency factors are numerically calculated when a Bessel light-sheet is incident, and the effects of beam’s order, and half-cone angle are mainly discussed. Numerical results show that there is strong point convergence in the forward scattering region under the incident of a Bessel light-sheet, and the internal and near-surface fields of Bessel light-sheet are very sensitive to the beam’s order, half-cone angle, etc. Such results have potential applications in the super-resolution imaging using a light-sheet microscopy.

Absorption of pulsed laser radiation by composites based on hexogen and aluminium nanoparticles

Absorption of the second-harmonic radiation from a pulsed YAG : Nd 3+ laser by composites based on hexogen and aluminium nanoparticles (of a diameter 100 nm) is theoretically and experimentally investigated. The absorption efficiency factor (the ratio of the light absorption cross section to the geometrical cross section) is calculated by using the Mie theory for Al inclusions in a hexogen medium for various particle diameters and wavelengths corresponding to laser fundamental and second-harmonic radiation. Dependences of the absorption coefficient and amplitude of an acoustic signal on the concentration of inclusions under laser irradiation of composite samples are measured by using a piezo-acoustic transducer. It is shown that the radiation is directly absorbed by nanoparticles. The optimal concentration is found, which provides the maximal signal of the piezo-acoustic transducer.

Micro hot-spot model of thermal explosion taking into account dielectric shell of sensitizing nanoparticle

The aim of this work is to modernize the micro hot-spot model of explosion decomposition laser initiation taking account optical and thermal properties of dielectric shell. The tasks are to modernize the micro hot-spot model of explosion decomposition taking into account the transparent dielectric shell of nanoparticle, which physical properties (complex refractive index, the coefficient of thermal conductivity) differ significantly from the properties of the material of nanoparticle nucleus; to calculate the efficiency factors of absorption and scattering of nanoparticles with the structure of the metal core – dielectric shell; to calculate the maximum temperature dependence on the radius of the nanoparticle at different thicknesses of the dielectric shell. Influence of oxide shell on the optical properties of the aluminium nanoparticles was studied in terms of Aden-Kerker and Mie theory for the spherical particle. It was shown that oxide shell changes drastically the optical properties of the nanoparticle, while the heating kinetics is influenced insignificantly.

Natural anisotropic nanoparticles with a broad absorption spectrum for solar energy harvesting

Optical properties of spherical nanoparticles, made of natural hyperbolic material-Bi2Te3, are studied numerically based on the Mie theory from the ultraviolet to the near-infrared region. The absorption efficiency factor of an anisotropic spherical nanoparticle is calculated by superimposing contributions from different polarizations. The numerical results show that Bi2Te3 nanoparticles exhibit broadband absorption in the wavelength range of 300–2400 nm with several absorption peaks, owing to the simultaneous excitation and superposition of electric and magnetic dipole resonances. In order to elucidate the mechanism of resonance absorption peaks of Bi2Te3 nanoparticles, the Mie theory is used to calculate the electric field inside these nanoparticles by assuming the nanoparticle to be isotropic, having the same dielectric function as either parallel or perpendicular dielectric function of Bi2Te3. It is shown that increasing the size of the Bi2Te3 nanoparticle causes a redshift of the resonance wavelength, an increase in the magnetic dipole absorption peak, and a decrease in the electric dipole absorption peak. The numerical results also show that Bi2Te3 nanoparticles have high absorption efficiency factor in the wavelength of 300–2400 nm, demonstrating their potential to be used for harvesting solar energy.

Theoretical modeling and analysis on the absorption cross section of the two-photon excitation in Rb.

The cross-section is crucial for quantitative characterization and analysis of the absorption process. A model on the absorption cross-section of the simultaneous two-photon excitation in Rb-vapor four-wave mixing process is established by using the coupled-wave equation. Taken into account of the hyperfine structures for 85Rb and 87Rb, the third-order susceptibility and hyperfine line strength are calculated respectively. Then, the influences of hyperfine transition on cross section are investigated and simulation results agree well with the experiment results. The calculated results suggest that high pumping power intensity is essential in Rb two-photon excitation, while narrow linewidth is the limiting factor of high absorption efficiency by comparing normalized absorption profile between pumping beam and two-photon excitation process. Additionally, two approaches to improving absorption efficiency, linewidth narrowness of the pumping beam and absorption linewidth broadening, are proposed.

Discrete dipole approximation for calculating optical properties of ZnO nanoparticles and ZnO-PVP composites

Discrete dipole approximation (DDA) is a well-known method which is generally used to simulate the interaction of nanoparticles with the electric field of incident light. In this paper, DDA has been used to simulate different optical properties (absorption efficiency factor, scattering efficiency factor, extinction efficiency factor, phase lag efficiency factor and 3D near electric field) of ZnO nanoparticles (NPs) and ZnO-PVP composite. The particle sizes are varied and size corrected complex dielectric function of ZnO and its composite have been used as inputs of the simulation. The particle sizes of ZnO NPs and ZnO-PVP composites have been varied from 22 nm to 38 nm in simulation. The peak position of absorption efficiency factor matches perfectly with the experimental absorbance when the size of ZnO NPs is taken as 26 nm. The same phenomenon happens in case of ZnO-PVP composite when the size of composite NPs is considered as 28 nm. The particle within dielectric medium acts as particle with higher effective radius as the near electric field increases due to presence of local dielectric medium. We have also calculated other optical parameters of ZnO NPs and ZnO-PVP composites. Small but not negligible changes in optical properties are observed due to incorporation of PVP with ZnO nanoparticles.