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This study examined spectroscopic, thermal, and other qualities, such as the lasing parameters, of Sm3+-doped glass with the composition 40P2O5–30ZnO–20LiCl–10BaF2. The ellipsometric data were used in a Sellmeier dispersion relation to estimate the refractive index values of the glasses investigated. The measured absorption spectra of the doped glass reveal the presence of various absorption bands assigned to transitions from the 6H5/2 ground state attributed to Sm3+-ion-excited states. We studied the decay of the 4G5/2 level of the Sm3+ ions in the doped glass by analyzing its absorption and emission fluorescence spectra. The Judd–Ofelt hypothesis allowed us to determine that the quantum efficiency of the 4G5/2–6H7/2 transition is high: 96% and 97% for glass doped with 4.05 × 1019 ions/cm−3 and 11 × 1019 ions/cm−3, respectively. Furthermore, this glass exhibits efficient red/orange enhanced spontaneous emission that matches the excitation band of the photosensitizer material used in medical applications. [ABSTRACT FROM AUTHOR]

In this paper, we study the critical impact parameter and Lyapunov exponent for a massive charged particle and a photon in the Kerr–Newman–de Sitter (KNdS) spacetime. From the geodesic equations obtained for the particle traveling parallel to the rotation axis (on-axis) of the KNdS spacetime and using the complex angular momentum (CAM) technique, it is found that the total absorption cross-section at a high-frequency limit oscillates with decreasing amplitude. We show that the black hole charge and spin affect the total absorption cross-section in the case of both the massive charged particle and photon. [ABSTRACT FROM AUTHOR]

In this work, we investigate the quasinormal modes (QNMs), shadow radius, gray-body factor, Hawking radiation and absorption cross-section of the Reissner–Nordström black hole surrounded by a cloud of strings in Rastall gravity for a massless scalar field. We use the sixth-order Wenzel, Kramers and Brillouin (WKB) and unstable circular null geodesic methods to calculate QNMs. Moreover, the values obtained by the two methods are in very good agreement. The real part and absolute value of imaginary part of quasinormal frequencies decrease with the increase of a. As q increases, the real part of quasinormal frequencies increases while the absolute value of imaginary part first increases and then decreases. For β > 0, they decrease with the increase of β. While they first increase and then decrease with β increasing at small value of a when β < 0. Then using the unstable circular null geodesic method, we obtain the shadow radius of black hole. We find that shadow radius decreases first and then increases as the negative parameter β increases. We also calculate the gray-body factor. According to it, Hawking radiation and absorption cross-section are calculated. We explore the influence of a, β and q on the energy emission rate. When other parameters are fixed, the black hole lives longer as a, positive parameter β and q increase. To obtain absorption cross-section, we adopt the partial wave method and sinc approximation method, and the results obtained by two methods have excellent consistency at mid-high frequency region. Further, we assess the effect of a, β and q on the absorption cross-section. [ABSTRACT FROM AUTHOR]

This study examined spectroscopic, thermal, and other qualities, such as the lasing parameters, of Sm3+-doped glass with the composition 40P2O5–30ZnO–20LiCl–10BaF2. The ellipsometric data were used in a Sellmeier dispersion relation to estimate the refractive index values of the glasses investigated. The measured absorption spectra of the doped glass reveal the presence of various absorption bands assigned to transitions from the 6H5/2 ground state attributed to Sm3+-ion-excited states. We studied the decay of the 4G5/2 level of the Sm3+ ions in the doped glass by analyzing its absorption and emission fluorescence spectra. The Judd–Ofelt hypothesis allowed us to determine that the quantum efficiency of the 4G5/2–6H7/2 transition is high: 96% and 97% for glass doped with 4.05 × 1019 ions/cm−3 and 11 × 1019 ions/cm−3, respectively. Furthermore, this glass exhibits efficient red/orange enhanced spontaneous emission that matches the excitation band of the photosensitizer material used in medical applications.

The absorption cross-section of Cr2+ ions in a range of cubic Zn1–xMnxSe (x = 0–0.3) solid solutions was determined using nonlinear transmission measurements. The maximum absorption cross-section of about 1.04 × 10–18 cm2 was determined and shown to be practically independent of the Mn content (x) in the solid solution. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the influence of the surface quantum effect on the absorption cross section and the field enhancement factor of core-shell plasmonic nanoparticles. We apply a quantum approach based on surface response functions (SRF)—Feibelman d-parameters and mesoscopic boundary conditions. The discrete sources method is implemented, which makes it possible to perform an efficient numerical analysis of scattering problems accounting for surface quantum effect. The simulation results demonstrate a significant influence of the surface quantum effect on the optical characteristics of core-shell plasmonic nanoparticles. In particular, the surface quantum effect exhibits plasmon resonance damping up to 15 , and the blue shift in the spectral domain can reach 10 nm. [ABSTRACT FROM AUTHOR]

All thermoplasmonic applications have an objective of significantly improving the photothermal conversion of spherical plasmonic nanoparticles, but different core sizes and shell thicknesses provide challenges. In order to examine novel and potential applications, a range of photothermal nanomaterials have been improved with superior light harvesting and photothermal conversion abilities. Here present work described the optical and thermoplasmonic properties of Fe and its oxide and Al and its oxide in spherical core-shell combination with core sizes varying between 20 and 50 nm, and two different shell thicknesses of 5 and 20 nm are investigated by the Mie theory in the water surrounding medium. It is revealed that the LSPR of distinct core-shell nanoparticles could be easily improved by changing the materials and also varying the core sizes as well as the shell thickness. The optical spectra are observed in the range of 230–637 nm wavelengths and merged in the UV-visible-near-infrared region on the electromagnetic (EM) spectrum. Maximum absorption and scattering cross-section are revealed at resonance wavelengths of 442 nm (Cabs≈2.75 × 10− 14 m2), and 337 nm (Csca≈4.95 × 10− 14 m2) for 20 nm shell thickness of Al@ Fe2O3. Further, the maximum temperature at the surface of the nanoparticle is observed at 4.13 0 C of Fe@Fe2O3, and 6.50 0 C of Al@ Fe2O3 with 5 and 20 nm shell thicknesses respectively. The maximum temperature rise and absorption power or heat generation is obtained for iron and its oxide in core-shell i.e. Fe@Fe2O3 NPs in the water environment. Moreover, the order of rising maximum temperature of considered NPs in distinct core-shell is as Fe@Fe2O3 > Al@Fe2O3 > Fe@Al2O3 > Al@Al2O3. Our findings provide a way to analyze the core-shell nanoparticle's potential in optical imaging, the biomedical field, therapeutics, and thermal nano-heaters under its LSPR characteristics. [ABSTRACT FROM AUTHOR]

We study the quasinormal modes, Hawking radiation and absorption cross-section of the Bardeen black hole surrounded by perfect fluid dark matter for a massless scalar field. Our results show that the oscillation frequency of quasinormal modes is enhanced as magnetic charge g or the dark matter parameter α increases. For damping rate of quasinormal modes, the influence of them is different. Specifically, the increase of dark matter parameter α makes the damping rate increasing at first and then decreasing. While the damping rate is continuously decreasing with the increase of the magnetic charge g. Moreover, we find that the increase of the dark matter parameter α enhances the power emission spectrum whereas magnetic charge g suppresses it. This means that the lifespan of black holes increases for smaller value of α and larger value of g when other parameters are fixed. Finally, the absorption cross-section of the considered black hole is calculated with the help of the partial wave approach. Our results suggest that the absorption cross-section decreases with the dark matter parameter α or the magnetic charge g increasing. [ABSTRACT FROM AUTHOR]

Investigation on intrinsic properties of photosynthetic pigment molecules participating in solar energy absorption and excitation, especially their eigen-absorption cross-section (σik) and effective absorption cross-section (σ'ik), is important to understand photosynthesis. Here, we present the development and application of a new method to determine these parameters, based on a mechanistic model of the photosynthetic electron flow-light response. The analysis with our method of a series of previously collected chlorophyll a fluorescence data shows that the absorption cross-section of photosynthetic pigment molecules has different values of approximately 10-21 m², for several photosynthetic organisms grown under various conditions: (1) the conifer Abies alba Mill., grown under high light or low light; (2) Taxus baccata L., grown under fertilization or non-fertilization conditions; (3) Glycine max L. (Merr.), grown under a CO2 concentration of 400 or 600 µmol CO2 mol-1 in a leaf chamber under shaded conditions; (4) Zea mays L., at temperatures of 30°C or 35°C in a leaf chamber; (5) Osmanthus fragrans Loureiro, with shaded-leaf or sun-leaf; and (6) the cyanobacterium Microcystis aeruginosa FACHB905, grown under two different nitrogen supplies. Our results show that σik has the same order of magnitude (approximately 10-21 m²), and σ'ik for these species decreases with increasing light intensity, demonstrating the operation of a key regulatory mechanism to reduce solar absorption and avoid high light damage. Moreover, compared with other approaches, both σik and σ'ik can be more easily estimated by our method, even under various growth conditions (e.g., different light environment; different CO2, NO2, O2, and O3 concentrations; air temperatures; or water stress), regardless of the type of the sample (e.g., dilute or concentrated cell suspensions or leaves). Our results also show that CO2 concentration and temperature have little effect on σik values for G. max and Z. mays. Consequently, our approach provides a powerful tool to investigate light energy absorption of photosynthetic pigment molecules and gives us new information on how plants and cyanobacteria modify their light-harvesting properties under different stress conditions. [ABSTRACT FROM AUTHOR]

In this work, we utilize the Wentzel–Kramers–Brillouin (WKB) approximation to determine the Hawking temperature corresponding to the Kerr–Newman–de Sitter (KNdS) spacetime. Specifically, we calculate the low frequency absorption cross-section for the KNdS black hole in a charged scalar field and analyzed its dependence on the characteristics of the black hole. Through our research, we have established a correlation between the absorption cross-section ( σ abs ) and the Hawking temperature ( T H ) of the black hole, demonstrating an inverse proportionality between the two quantities. Furthermore, we also deduce the absorption cross-sections for Kerr–de Sitter, Reissner–Nordstrom–de Sitter, Schwarzschild–de Sitter and Schwarzschild black holes, and compare them with previously obtained results. The validity of our findings is demonstrated by these comparisons. [ABSTRACT FROM AUTHOR]

Investigation on intrinsic properties of photosynthetic pigment molecules participating in solar energy absorption and excitation, especially their eigen-absorption cross-section (σik) and effective absorption cross-section (σ′ik), is important to understand photosynthesis. Here, we present the development and application of a new method to determine these parameters, based on a mechanistic model of the photosynthetic electron flow-light response. The analysis with our method of a series of previously collected chlorophyll a fluorescence data shows that the absorption cross-section of photosynthetic pigment molecules has different values of approximately 10−21 m2, for several photosynthetic organisms grown under various conditions: (1) the conifer Abies alba Mill., grown under high light or low light; (2) Taxus baccata L., grown under fertilization or non-fertilization conditions; (3) Glycine max L. (Merr.), grown under a CO2 concentration of 400 or 600 μmol CO2 mol−1 in a leaf chamber under shaded conditions; (4) Zea mays L., at temperatures of 30°C or 35°C in a leaf chamber; (5) Osmanthus fragrans Loureiro, with shaded-leaf or sun-leaf; and (6) the cyanobacterium Microcystis aeruginosa FACHB905, grown under two different nitrogen supplies. Our results show that σik has the same order of magnitude (approximately 10−21 m2), and σ′ik for these species decreases with increasing light intensity, demonstrating the operation of a key regulatory mechanism to reduce solar absorption and avoid high light damage. Moreover, compared with other approaches, both σik and σ′ik can be more easily estimated by our method, even under various growth conditions (e.g., different light environment; different CO2, NO2, O2, and O3 concentrations; air temperatures; or water stress), regardless of the type of the sample (e.g., dilute or concentrated cell suspensions or leaves). Our results also show that CO2 concentration and temperature have little effect on σik values for G. max and Z. mays. Consequently, our approach provides a powerful tool to investigate light energy absorption of photosynthetic pigment molecules and gives us new information on how plants and cyanobacteria modify their light-harvesting properties under different stress conditions.

Hydrogen cyanide (HCN) is a major source of prompt-NO x formation especially in fuel-bound nitrogen systems. To date, there is still a significant disagreement between experimental data and theoretical predictions of the rate coefficients of combustion reactions involving HCN as a prompt-NO x precursor. Accurate modeling of NO x formation would greatly benefit from a diagnostic capable of performing high-fidelity measurements of HCN formation/consumption time-histories. In this study, a laser diagnostic is developed for sensitive and selective HCN sensing by probing its most intense absorption feature in the mid-infrared (MIR). The diagnostic is based on difference-frequency generation (DFG) between a CO 2 gas laser and an external-cavity quantum cascade laser in a nonlinear orientation-patterned gallium arsenide crystal which results in a DFG laser tunable over 11.56 − 15 µm. HCN measurements were carried out at the peak of the Q -branch of its strong ν 2 vibrational band near 14 µm. Pressure dependence of the absorption cross-section was investigated at room temperature over the pressure range of 0.07 − 1.07 bar. Temperature-dependent absorption cross-section measurements were conducted behind reflected shock waves over the temperature range of 850 − 3000 K. The diagnostic was demonstrated in reactive experiments in a shock tube where HCN mole fraction time-histories were measured during the thermal decomposition of isoxazole (C 3 H 3 NO) and the first-order rate coefficients of C 3 H 3 NO → HCN + CH 2 CO reaction were determined. [ABSTRACT FROM AUTHOR]

The article describes a new practical model for the infrared absorption of chlorofluorocarbons and other gases with dense spectra, based on high‐resolution transmission molecular absorption database (HITRAN) absorption cross‐sections. The model is very simple, consisting of frequency‐dependent polynomial coefficients describing the pressure and temperature dependence of absorption. Currently it is implemented for the halocarbon species required by the Radiative Forcing Model Intercomparison Project. In cases where cross‐section data is available at a range of different temperatures and pressures, this approach offers practical advantages compared to previously available options, and is traceable, since the polynomial coefficients follow directly from the laboratory spectra. The new model is freely available and has several important applications, notably in remote sensing and in developing advanced radiation schemes for global circulation models that include halocarbon absorption. For demonstration, the model is applied to the problem of computing instantaneous clear‐sky halocarbon radiative efficiencies and present day radiative forcing. Results are in reasonable agreement with earlier assessments that were carried out with the less explicit Pinnock method, and thus broadly validate that method. Plain Language Summary Chlorofluorocarbons and other related gases have dense and complicated absorption spectra that can be measured in the laboratory. We bring such measurements to a form that can be used for simulations of the transfer of radiation through the atmosphere. Then we use the new model to calculate new estimates of the climate impact of these man‐made gases. The results broadly validate earlier calculations that were done with a less explicit method. Plain Language Summary: Chlorofluorocarbons and other related gases have dense and complicated absorption spectra that can be measured in the laboratory. We bring such measurements to a form that can be used for simulations of the transfer of radiation through the atmosphere. Then we use the new model to calculate new estimates of the climate impact of these man‐made gases. The results broadly validate earlier calculations that were done with a less explicit method. Key Points: A new polynomial model for laboratory absorption cross‐section data was developedThe new model was used to compute instantaneous clear‐sky halocarbon radiative efficiencies and present day radiative forcingHalocarbons are found to contribute approximately 20% of the total anthropogenic instantaneous clear‐sky forcing [ABSTRACT FROM AUTHOR]

An influence of the adsorbed molecules layer on the optical characteristics of the spherical metallic nanoparticles has been studied in the work. In order to do this one considers the additional term which takes into account the scattering of electrons at the interface between metal and adsorbate. The analytical expressions for the frequency dependences for the parameter of coherence loss due to the scattering at the interface "metal - adsorbed layer" have been obtained. It has been found that the presence of the adsorbed molecules results in the electron scattering anisotropy, and, hence, in the anisotropy of the optic response of such systems. The result of the indicated anisotropy is the appearance of the additional maximum in the infrared part of the spectrum in the frequency dependences for the optical characteristics. An evolution of the frequency dependences for the components of the polarizability tensor and the absorption cross-section and scattering cross-section for the two-layer spherical nanoparticles of the type "metal - adsorbate" under the variation of their geometrical parameters has been analyzed. It has been shown that the weak maximum of the real, imaginary parts and the module of the transverse component of the polarizability tensor and the absorption and scattering cross-sections in the infrared part of the spectrum appears due to inducing of the local density of the states by adsorbate. The reason of the shift of the maxima of the absorption cross-section and scattering cross-section for the nanoparticles of the constant sizes with the cores of different metals has been found. It has been demonstrated the existence of the small-scale oscillations at the frequency dependences for the components of the polarizability tensor and at the absorption and scattering cross-sections, caused by an oscillating contribution of the surface electron scattering. The dependence of the location and the value of the maximum of the absorption cross-section for the particle "metal - adsorbate" with the constant geometrical parameters and content on the dielectric permittivity of the medium, in which the nanoparticle is situated, has been proved. [ABSTRACT FROM AUTHOR]

The behavior of the diagonal components of the dielectric tensor and the behavior of the absorption crosssection in the different frequency ranges for the composite cylindrical nanostructures "metallic core - graphene shell" have been studied. In order to obtain the calculation formulas one uses the relations for the longitudinal and transverse components of the dielectric tensors for metallic core and graphene shell, which are determined by Drude model and Cubo model correspondingly. The consideration is carried out in the frameworks of "equivalent" elongated spheroid approach, according to which the defining dimensional parameter is effective aspect ratio, calculated from the condition of the equality of the corresponding axial inertia moments for two-layer cylinder and the "equivalent" elongated spheroid. The numerical results have been obtained for the nanocylinders with the cores of different metals, different radius and with the different number of graphene layers. The variation of amplitude and the variation of the location of extremes of the real and imaginary parts of the transverse component of the dielectric tensor under the increase in radius of the metallic core and the thickness of the graphene shell have been analyzed. It has been shown that the variation of the radius of the core has the significantly greater influence on the properties of the polarizability resonances and absorption cross-section than the variation of the number of graphene layers. The reasons of the presence of two maxima of the absorption cross-section for the metal-graphene cylinders which differ in both amplitude and width and located in infrared, violet and near ultraviolet parts of the spectrum and their relation with the surface plasmonic resonances in the metallic core and with the terahertz plasmons of graphene have been found. The factors which have an effect on amplitude and on the shift of the maxima of the absorption cross-section have been found. The reasons of the different width of maxima, which are located in the different spectral intervals, have been determined. [ABSTRACT FROM AUTHOR]

Single-stage processing of high-quality transparent functional polycrystalline ceramics is desirable but challenging. In the present work, spark plasma sintering (SPS) was employed for fabrication of Co2+:MgAl 2 O 4 saturable absorbers for laser passive Q-switching. Densification of commercial MgAl 2 O 4 powders, doped via co-precipitation, was carried out by conventional SPS and high-pressure SPS (HPSPS) under pressures of 60 and 400 MPa, respectively. The presence of LiF, a common sintering additive, was detrimental to optical properties as it promoted reaction of cobalt with sulfur impurities and the formation of Co 9 S 8 inclusions. Densification by HPSPS without LiF allowed to obtain highly transparent Co2+:MgAl 2 O 4. The optical properties of samples, with doping concentrations varying between 0.01 and 0.1 at.% Co2+, were assessed and saturable absorption was demonstrated at ~1.5 µm wavelength, exhibiting ground-state (σ gs) and excited (σ es) cross-sections of 3.5×10-19 and 0.8×10-19 cm2, respectively. Thus, it was established that HPSPS is an effective method to fabricate transparent Co2+:MgAl 2 O 4 ceramics. • Commercial MgAl 2 O 4 nano-powders were doped with Co2+ by co-precipitation. • Highly transparent 0.01–0.1 at% Co2+:MgAl 2 O 4 ceramics were fabricated by HPSPS. • Conventional SPS was not a viable method to produce Co2+:MgAl 2 O 4 ceramics. • LiF sintering additive induced reaction of Co with S which formed Co 9 S 8 inclusions. • HPSPS-processed Co2+:MgAl 2 O 4 can serve as laser passive Q-switch medias. [ABSTRACT FROM AUTHOR]

• Absorption non-uniformities within aggregates increase with increasing aggregate sizes, and may contribute to excessive absorption and anomalous cooling effects observed in TiRe-LII experiments on metal nanoparticles. • For the aggregates considered, primary particles within the aggregate may be shielded from the E-field at certain orientations leading to a larger degree of absorption and emission non-uniformity, however, orientation has a less than 10 % impact on the random orientation value. • Sintering-induced overlap can enhance the absorption properties of the aggregate due to increased electrical conductivity and morphological changes towards an elongated structure that promotes the antenna effect. Analyzing time-resolved laser-induced incandescence (TiRe-LII) data from metal nanoparticle aerosols requires a detailed understanding of their absorption and emission characteristics. This work investigates how non-uniform absorption within metal nanoparticle aggregates, aggregate morphology and orientation, and sintering of primary particles may affect TiRe-LII signals from metal nanoparticle aerosols. The multi-sphere T-matrix method is used to compute the absorption properties of aggregates with point contact between primary particles, while the discrete dipole approximation method is used when primary particles overlap. It was found that absorption non-uniformities within aggregates increase with increasing aggregate sizes, and may contribute to excessive absorption and anomalous cooling effects. For the anisotropic aggregates considered, the total absorption cross-section depends weakly on orientation. It was also found that the sintering of primary particles can enhance the absorption cross-section of metal aggregates. [ABSTRACT FROM AUTHOR]

Plasmonic interaction of nanoparticles located in close proximity, embedded in breast tissue, is simulated for estimating the optical characteristics like optical absorption cross-section, plasmonic wavelength as well as full-width half maxima (FWHM). The computations are done for the monomers, homodimers, and heterodimers of spherical and rod-shaped gold nanoparticles considering various interparticle spacings for gold nanospheres and the interparticle spacing as well as the orientation for gold nanorods (GNRs). The results indicate that for the spherical dimer, with the change in interparticle spacing from 1 to 20 nm, the peak absorption cross-section decreases by 43%. Whereas for the GNRs, the absorption cross-section increases/decreases, within 9–18%, depending on the homodimer or heterodimer configuration. Furthermore, secondary peaks for the absorption cross-section are obtained within wavelengths of 630–940 nm due to antibonding modes for GNR heterodimers. For GNR heterodimer located end-to-end, this secondary peak for the absorption cross-section appears at 780 nm irrespective of interparticle spacing within 1–5 nm. The absorption coefficient is considerably dependent on the configuration and proximity of GNRs located within the tissue. While FWHM is not significantly influenced by GNRs configuration and interparticle spacing. For interparticle spacing from 1 to 20 nm, the plasmonic wavelength shifts by 38 nm for the spherical dimer and by 35–86 nm for various GNR dimers. The findings of this study are useful for plasmonic photothermal therapeutics as the heat generation is governed by the resulting absorption cross-section due to plasmonic coupling of the closely spaced and different orientations of the nanoparticles. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of shape and size of core on the plasmonic response of spherical ZnO@Au core-shell nanostructures embedded in a passive host matrices of MgF2 within the framework of the qausistatic approximation. The absorption cross-section and local field enhancement factor of spherical ZnO@Au core-shell nanostructures are effectively studied by optimizing the parameters for a fixed composite diameter of 20 nm. In this two-layered core-shell nanostructures, four plasmonic resonances are found; the first two resonances associated with ZnO/Au and Au/MgF2 interfaces, whereas the third and fourth resonances are associated with the transverse and longitudinal modes, respectively. The peaks position and intensity of these resonances are varied by optimizing the shape and size of the core material. The tunability of the plasmon resonances of the composite systems enables it to exhibit very interesting material properties in a variety of applications extending from the visible to infrared spectral regions.

The cross-section of the infrared (IR) absorption of the Ge-O stretching mode in both GeO2 and GeOx films was determined. The GeO2 film was obtained by thermal oxidation of germanium while the GeOx film was obtained by physical vapor deposition. The latter was then annealed at a temperature of 550 °C for 30 min. Both the as-deposited and the annealed films were studied using IR absorption spectroscopy, Raman spectroscopy, ellipsometry and X-ray photoelectron spectroscopy. We found the absorption cross-section is about 2 ÷ 2.6·10–19 cm−2 for the GeO2 films and 0.8·10−19 cm−2 for the GeOx (x ∼ 1.1) film.

The expression for absorption cross-section of massless as well as massive charged particles in the background of dilaton-axion black hole is determined in low and high frequency limits. The modification of the absorption cross-section in comparison to Reissner-Nordstrom black hole is discussed. [ABSTRACT FROM AUTHOR]

The problem of absorption by a resonator of a gravity wave that propagates on the surface of an incompressible fluid is solved. The resonator is small as compared with the wavelength. For the free fluid surface the resonance, i.e., maximally possible, absorption cross-sections of resonators of various types are found. It is shown that the resonance absorption cross-section depends only on the wavelength. The problem of absorption of a gravity wave propagating in a channel is also considered. It is shown that the joint usage of monopole and dipole resonators ensures the total absorption of wave energy in the channel whose width is not greater than the wavelength. [ABSTRACT FROM AUTHOR]

The possibility of using heating of body tissue upon excitation of surface plasmons in two-layer spherical metal-graphene nanoparticles for thermal destruction of malignant neoplasms has been analyzed. Drude and Kubo models have been used to determine the frequency dependences of the dielectric function of the metal core and the conductivity of the graphene shell, respectively, and the distributions of temperatures in tumor tissue and surrounding healthy tissue have been determined by solutions of nonhomogeneous thermal conductivity equations. Values of thermophysical parameters of tumor tissue and healthy human tissue known from the literature have been used for numerical estimates and calculations. The evolution of the frequency dependences of the polarizability and absorption cross-sections of the indicated nanoparticles with the variation of the radius and material of the metal core and the thickness of the graphene shell has been studied. It has been shown that an increase in the radius of the metal core or thickness of the graphene shell results in an increase in the maximum values of the imaginary part of the polarizability and absorption cross-section, which is associated with increased interaction with the electromagnetic wave with increasing bulk metal content in the composite nanoparticle and with high concentration of free electrons in graphene layers. The possibility of spectral shifts of the polarizability maxima and the absorption cross-section with the variation of the core material of a two-layer nanoparticle, due to the essential difference in the values of the frequencies of bulk plasmons and the contribution of the ion core to the dielectric function, has been demonstrated. It has been established that the thermal conductivity is quasi-steady in the problem of heating of body tissue upon excitation of surface plasmon resonance in a composite nanoparticle. It has been proved that this method of cancer therapy is harmless to healthy tissue surrounding the tumor due to their extremely low heat. The results of numerical modeling demonstrate the need to use a conglomerate of metal-graphene nanoparticles in order to increase the effectiveness of therapy. [ABSTRACT FROM AUTHOR]

The electromagnetic field enhancement mechanisms leading to surface-enhanced Raman scattering (SERS) of R6G molecules near Ti 3 C 2 T x MXene flakes of different shapes and sizes are analyzed theoretically in this paper. In COMSOL simulations for the enhancement factor (EF) of SERS, the dye molecule is modeled as a small sphere with polarizability spectrum based on experimental data. It is demonstrated, for the first time, that in the wavelength range of500 nm-1000 nm, the enhancement of Raman signals is largely conditioned by quadrupole surface plasmon (QSP) oscillations that induce a strong polarization of the MXene substrate. We show that the vis-NIR spectral range quadrupole SP resonances are strengthened due to interband transitions (IBTs), which provide EF values of the order of 10 5 -10 7 in agreement with experimental data. The weak sensitivity of the EF to the shape and size of MXene nanoparticles (NPs) is interpreted as a consequence of the low dependence of the absorption cross-section of QSP oscillations and IBT on the geometry of the flakes. This reveals a new feature: the independence of EF on the geometry of MXene substrates, which allows to avoid the monitoring of the shape and size of flakes during their synthesis. Thus, MXene flakes can be advantageous for the easy manufacturing of universal substrates for SERS applications. The electromagnetic SERS enhancement is determined by the 'lightning rod' and 'hot-spot' effects due to the partial overlapping of the absorption spectrum of the R6G molecule with these MXene resonances., (Creative Commons Attribution license.)

In this paper, we investigated the effect of shape and size of core on the plasmonic response of spherical ZnO@Au core-shell nanostructures embedded in a passive host matrices of MgF2 within the framework of the qausistatic approximation. The absorption cross-section and local field enhancement factor of spherical ZnO@Au core-shell nanostructures are effectively studied by optimizing the parameters for a fixed composite diameter of 20 nm. In this two-layered core-shell nanostructures, four plasmonic resonances are found; the first two resonances associated with ZnO/Au and Au/MgF2 interfaces, whereas the third and fourth resonances are associated with the transverse and longitudinal modes, respectively. The peaks position and intensity of these resonances are varied by optimizing the shape and size of the core material. The tunability of the plasmon resonances of the composite systems enables it to exhibit very interesting material properties in a variety of applications extending from the visible to infrared spectral regions. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of shape and size of core on the plasmonic response of spherical ZnO@Au core-shell nanostructures embedded in a passive host matrices of MgF2 within the framework of the qausistatic approximation. The absorption cross-section and local field enhancement factor of spherical ZnO@Au core-shell nanostructures are effectively studied by optimizing the parameters for a fixed composite diameter of 20 nm. In this two-layered core-shell nanostructures, four plasmonic resonances are found; the first two resonances associated with ZnO/Au and Au/MgF2 interfaces, whereas the third and fourth resonances are associated with the transverse and longitudinal modes, respectively. The peaks position and intensity of these resonances are varied by optimizing the shape and size of the core material. The tunability of the plasmon resonances of the composite systems enables it to exhibit very interesting material properties in a variety of applications extending from the visible to infrared spectral regions. [ABSTRACT FROM AUTHOR]

The analysis of the photoabsorption spectra of molecules shows that the band maximum is usually redshifted in comparison to the vertical excitation. We conducted a throughout analysis of this shift based on low-dimensional analytical and numerical model systems, showing that its origin is rooted in the frequency change between the ground and the excited states in multidimensional systems. Moreover, we deliver a benchmark of ab initio results for the shift based on a comparison of vertical excitations and band maxima calculated with the nuclear ensemble approach for the 28 organic molecules in the Mülheim molecular dataset. The mean value of the shift calculated over 60 transitions is 0.11 ± 0.08 eV. The mean value of the band width is 0.32 ± 0.14 eV. [ABSTRACT FROM AUTHOR]

Perfluoro-n-propane, perfluorocyclobutane, perfluoro-n-butane, and perfluoro-n-pentane are non-ozone-depleting industrial alternatives to chlorofluorocarbons and hydrochlorofluorocarbons. However, these perfluoroalkanes have significant band strength in the atmospheric window from 800 to 1200 cm−1. Coupled with their millennial-scale atmospheric lifetimes, they can lead to significant long-term global warming. Infrared spectra are required to quantify the climate impacts. This work provides a set of high-temperature infrared absorption cross-sections in the range 298–350 K at 0.1 cm−1 resolution from 515 to 1500 cm−1 for each compound. Our cross-sections generally agree with literature measurements except for perfluoro-n-pentane. We use density functional theory to calculate the absorption cross-sections from 0 to 515 cm−1 using the B3LYP functional and several basis sets. The 6-31G(d,p) basis set provides the best results for linear perfluoroalkanes, while the def2-TZVP basis set provides the best results for cyclic perfluoroalkanes. Using experimental cross-sections, we calculate the radiative efficiency and global warming potential for each compound, utilizing the Pinnock curve from Shine and Myhre (2020) and atmospheric lifetimes from Hodnebrog et al. (2020). These quantities are found to be independent of temperature. The average 100-year global warming potential derived from all cross-sections is 9,610±1,260, 10,800±1,420, 10,100±1,330, and 9,380±1,230 for perfluoro-n-propane, perfluorocyclobutane, perfluoro-n-butane, and perfluoro-n-pentane, respectively. Combining the data in this work with our previous measurements reveals that the global warming potential for perfluoroalkanes with an increasing number of C F bonds depends on the ratio of radiative efficiency to molecular weight. [Display omitted] • Measured n-C 3 F 8 , n-C 4 F 10 , and n-C 5 F 12 cross-sections from 515–1500 cm−1 and 298–350 K. • Improved n-C 5 F 12 cross-sections compared to literature using a 99% pure sample. • Determined conformer populations for all compounds using density functional theory. • Investigated band strength and climate metrics trends with an increasing number of C F bonds. • Showed temperature independence of integrated cross-sections and climate metrics. [ABSTRACT FROM AUTHOR]

In this paper, we present the revision of the cross-section database used for the retrieval of aerosol and gas species from remote sensing measurements by the GOMOS instrument onboard ENVISAT. The absorption cross-section spectra concern ozone, nitrogen dioxide and nitrogen trioxide, for which improved datasets have been published since the implementation of the original GOMOS cross-section database in preparation of the ENVISAT mission. We evaluate the molecular absorption cross-section spectra currently available for O3, NO2 and NO3, and we present and discuss our selection of datasets and the set-up of the revised absorption cross-section database, with the focus on these three gases. The objective is to provide an optimal characterization of their absorption spectrum over the UV-visible-near IR range used by AerGOM, a retrieval algorithm that was designed to optimize the retrieval of aerosol species from GOMOS measurements. Despite its application to the specific case of GOMOS, it is the aim of this work to cover a more general scope than this particular mission, and to provide an evaluation applicable to any other case of remote sensing experiment covering the UV to near IR range, possibly with a high spectral resolution.

Benzene is a very important molecule in a variety of industrial, environmental, and chemical systems. In combustion, benzene plays an essential role in the formation and growth of polycyclic aromatic hydrocarbons and soot. In this work, a new laser-based diagnostic is presented to make quantitative, interference-free, and sensitive measurements of benzene in the mid-infrared (MIR) region. The diagnostic is based on a widely tunable difference-frequency-generation (DFG) laser system. We developed this laser source to emit in the MIR between 666.54 cm−1 and 790.76 cm−1 as a result of the DFG process between an external-cavity quantum-cascade-laser and a CO 2 gas laser in a nonlinear, orientation-patterned GaAs crystal. Benzene measurements were carried out at the peak (673.94 cm−1) of the Q-branch of the ν 11 vibrational band of benzene. The absorption cross-section of benzene was measured over a range of pressures (4.44 mbar to 1.158 bar) at room temperature. The temperature dependence of the absorption cross-section was studied behind reflected shock waves over 553–1473 K. The diagnostic was demonstrated in a high-temperature reactive experiment of benzene formation from propargyl radicals. The new diagnostic will prove highly beneficial for high-temperature studies of benzene formation and consumption kinetics. [ABSTRACT FROM AUTHOR]

Absorption of solar radiation by water vapor in the near‐UV region is a poorly understood but important issue in atmospheric science. To better understand water vapor near‐UV absorption, we constructed a cavity ring‐down spectrometer with bandwidth of 5 cm−1 (~0.05 nm) and obtained water vapor absorption cross sections at 1‐nm increments in the 290‐ to 350‐nm region. Water vapor displays structured absorption over this range with maximum and minimum cross sections of 8.4 × 10−25 and 1.6 × 10−25 cm2/molecule. Major water vapor absorption bands were observed at 293–295, 307–313, 319, 321–322, and 325 nm, with cross‐section values higher than 4.0 × 10−25 cm2/molecule. To obtain further insight into major water vapor absorption bands, we measured water vapor absorption cross sections at 0.05‐nm intervals in the 292‐ to 296‐nm, 306‐ to 314‐nm, and 317‐ to 326‐nm region. Field UV residual spectra not only exhibited increased attenuation at higher atmospheric water vapor loadings but also showed structures suggested by the laboratory water vapor absorption spectrum. Spaceborne UV radiance spectra have spectral structures resembling the differential cross‐section spectrum constructed from the laboratory wavelength‐dependent water vapor absorption cross sections presented here. Incorporating water vapor absorption cross‐section data into a radiative transfer model yielded an estimated energy budget of 0.26 W/m2 for the standard U.S. atmosphere and 0.76 W/m2 for the tropics. This shows that water vapor near‐UV absorption is an important contributor for climate simulation and ozone retrievals. Plain Language Summary: Water vapor near‐UV absorption is an overlooked subject of core importance to atmospheric science. We constructed a cavity ring‐down spectrometer with a bandwidth comparable to those of field UV spectrometers and determined water vapor absorption cross sections at 1‐nm intervals in the 290‐ to 350‐nm region. We also measured water vapor absorption cross sections at 0.05‐nm intervals surrounding major absorption bands. We provide field evidence to support laboratory water vapor near‐UV absorption measurements and present comparisons of the estimated optical depth spectra of ozone with those of water vapor for the standard U.S. and tropical atmospheres. Our findings suggest that water vapor near‐UV absorption will significantly affect ozone retrieval from UV measurements, particularly in the tropical region. Incorporating cross‐section data into a radiative transfer model, we estimated that the energy budget of water vapor near‐UV absorption was about 0.26 W/m2 for the standard U.S. atmosphere and 0.76 W/m2 for the tropics. Since it was not thought that water vapor could have near‐UV absorption, the effect of such absorption is not currently included in radiation and climate simulation models. Our work on water vapor near‐UV absorption is expected to change the paradigm in atmospheric measurements from UV remote sensing observations and how atmospheric radiation and climate are modeled. Key Points: Water vapor displays structured absorption bands over the 290‐ to 350‐nm range, with cross sections in the range of 10−24 to 10−25 cm2/moleculeField evidence for water vapor near‐UV absorption is presentedWater vapor near‐UV absorption affects O3 retrieval and modeling of atmospheric radiation and climate [ABSTRACT FROM AUTHOR]

This paper discuss a possibility for using a thin-film functional coating based on transparent conducting thin films of aluminum doped zinc oxide (AZO) as a heat-eliminating material on the surface of a spacecraft. The structure of the functional coating has been chosen taking into account the plasmonic properties of AZO and silver and represents the AZO slabs with embedded silver nanoparticles deposited on AZO layer and AZO slabs with embedded silver nanoparticles deposited on thin film fused quartz layer. The paper contains COMSOL finite element simulations of the scattering cross section for thermal radiation in the IR band in the case the investigated coating deposited on a reflective aluminum film, and absorption cross section in the near UV and visible spectral bands when the coating deposited on silicon solar panels. The calculations demonstrate an increase in the scattering cross-section in the spectral band of blackbody radiation by several orders of magnitude, with the maximum in the scattering spectrum of the AZO slabs/ AZO /Al structure corresponding to the maximum intensity of the blackbody thermal radiation, which has been heated to 100 °C in the case the lattice period of the AZO slabs is equal to the resonance wavelength for AZO. Also an increase in the absorption cross-section of AZO slabs/ AZO /Si structure in visible spectral band is observed corresponding to plasmon absorption of embedded silver nanoparticles. • Plasmon effects in ZnO:Al layers can solve the thermal problems for spacecraft. • ZnO:Al is functional material with plasmon resonances in the near IR spectral band. • ZnO:Al is a heat-eliminating material on the surface of a spacecraft. • Metal nanoparticles embedded into the AZO increase the efficiency of solar panels. [ABSTRACT FROM AUTHOR]

This work presents broadband spectrally resolved measurements of the absorption cross-section of NO 2 from approximately 430 to 500 or 580 nm, depending on temperature, with a spectral resolution of approximately 0.06 nm. An ultrafast-laser-absorption-spectroscopy (ULAS) diagnostic was developed and used to provide broadband (up to approximately 900 cm−1 per laser shot) cross-section measurements with sub-nanosecond time resolution. Cross-section measurements were acquired from 430 to 580 nm in a heated gas cell at temperatures of 296 K and 670 K and a pressure of 1.5 bar. Cross-section measurements were also acquired behind reflected shock waves at temperatures near 970 K, 1150 K, and 1450 K at pressures near 1.5 bar. A quantum-cascade-laser-absorption diagnostic for NO was used to measure NO mole fraction at 500 kHz and determine the extent of NO 2 decomposition in shock-tube experiments. The measured cross-sections typically exhibit good agreement with prior measurements available at select wavelengths and conditions as well as with recently developed theoretical predictions at most wavelengths and temperatures studied. A detailed description of the experimental and data processing procedures that enabled the ULAS measurements despite pronounced variations in laser pulse energy and the absence of non-resonant wavelengths within the pulse bandwidth are also presented. • Femtosecond absorption spectroscopy measurements of NO 2 at high temperatures. • Broadband absorption cross-section measurements of NO 2 from 430 to 500 nm. • First broadband absorption cross-section measurements of NO 2 reported at up to 1450 K. [ABSTRACT FROM AUTHOR]

Optical transition and near-infrared upconversion luminescence properties of Er3+ single-doped and Er3+, Yb3+ co-doped YNbO 4 phosphors are reported. Based on the framework of Judd-Ofelt theory and modified Judd-Ofelt calculation method, the optical transition properties of Er3+ and Yb3+ ions in YNbO 4 : Er3+, Yb3+ sample were studied, respectively. The calculated results showed that the absorption cross-section of Er3+ ion at ∼1550 nm is larger than that at ∼980 nm in YNbO 4 : Er3+ phosphor. And, the absorption cross-section of 2F 7/2 → 2F 5/2 transition of Yb3+ in YNbO 4 : 15.0 mol% Er3+, 15.0 mol% Yb3+ sample was calculated to be 138.70 × 10−20 cm2. According to the emission cross section of Er3+ (4I 11/2 → 4I 15/2) and the absorption cross section of Yb3+ (2F 7/2 → 2F 5/2), the energy transfer rates from Er3+ to Yb3+ were quantitatively analyzed via the Föster-Dexter model. Furthermore, 1550 nm was selected as the excitation wavelength, the near-infrared upconversion emission spectra of YNbO 4 : Er3+, Yb3+ samples were measured. It was found that the sample has strong emission at ∼980 nm and the emission intensity was still enhanced with the incorporation of Yb3+. • YNbO 4 : Er3+, Yb3+ phosphors were synthesized via a solid-state reaction method. • The absorption cross section of Yb3+ in YNbO 4 phosphor was confirmed. • The energy transfer rates from Er3+ to Yb3+ in YNbO 4 phosphors were calculated. • The YNbO 4 : Er3+, Yb3+ sample has strong ∼980 nm emission excited by 1550 nm. [ABSTRACT FROM AUTHOR]

Abstract The electronic structures of triplet S 2 ground and excited states are studied by ab initio molecular orbital and configuration interaction calculation. Potential energy curves correlated with S ( 3 P) + S ( 3 P) and S ( 3 P) + S ( 1 D) at the dissociation limit are evaluated, and electronic terms for a total of 11 states are assigned. Transition dipole moments, as a function of internuclear distance, are determined for two allowed transitions to B ″ 3 Π u and B 3 Σ u - excited states. The total absorption cross-sections are computed to estimate isotope-fractionation constants, ε , for four most common isotopologues: 32 S 32 S , 32 S 33 S , 32 S 34 S , and 32 S 36 S by quantum close-coupling (R-matrix) expansion approach and they are found to lie in a mostly opaque to competing absorbers spectral window. We suggest that the photochemistry and isotopic effects of S 2 are of significant importance and provide data showing high sensitivity of mass-independent fractionation to excitation wavelength. Zero-point energy based constants ε ZPE are estimated as well to compare with the obtained isotope effects and two modes for MIF are present in three-isotope plots; large isotopic effects were observed for both 36 S and 33 S with an excitation wavelength-dependent fluctuation. [ABSTRACT FROM AUTHOR]

Spectrally resolved ultraviolet (UV) absorption cross-sections of gas-phase sodium chloride (NaCl), potassium hydroxide (KOH), and sodium hydroxide (NaOH) were measured, for the first time, in hot flue gases at different temperatures. Homogenous gas-phase NaCl, KCl (potassium chloride), NaOH, and KOH at temperatures 1200 K, 1400 K, 1600 K, and 1850 K were prepared in the post-flame zone of laminar flames by seeding nebulized droplets out of aqueous solution of corresponding alkali species. The amount of droplets seeded into the flame was kept constant, so the relative concentration of different alkali species can be derived. The broadband UV absorption cross-section of KCl vapor reported by Leffler et al. was adopted to derive the absorption cross-section curves of NaCl, NaOH, and KOH with the corresponding measured spectrally resolved absorbance spectra. No significant changes in the spectral structures in the absorption cross-sections were found as the temperature varied between 1200 K and 1850 K, except for NaOH at around 320 nm. The difference between the absorption spectral curves of alkali chlorides and hydroxides is significant at wavelengths above 300 nm, which thus can be used to distinguish and obtain the concentrations of alkali chlorides and hydroxides in the broadband UV absorption measurements. [ABSTRACT FROM AUTHOR]

HFC-43-10mee (C 5 H 2 F 10 ) is a substitute for CFC-113, HCFC-141b and methyl chloroform, as well as an alternative to perfluorocarbons with high radiative efficiencies. Recent observations have shown that the global mean tropospheric abundance of HFC-43-10mee has increased steadily from the 1990s to reach 0.211 ppt in 2012. To date, the emission of this compound is not regulated. The radiative efficiency (RE) of HFC-43-10mee has recently been re-evaluated at 0.42 W m −2 ppb −1 , giving a 100-year time horizon global warming potential (GWP 100 ) of 1650. However, the initial RE, from which the new values were derived, originated from an unpublished source. We calculated a new RE of 0.36 W m −2 ppb −1 and a GWP 100 of 1410 from laboratory absorption cross-section spectra of a pure vapour of HFC-43-10mee. Acquisitions were performed in the 550–3500 cm −1 spectral range using Fourier transform spectroscopy. The results were compared with the broadened spectra from the Pacific Northwest National Laboratory (PNNL) database and with theoretical calculations using density functional theory. [ABSTRACT FROM AUTHOR]

This paper presents a method for determination of the size distribution for diamond nanocrystals containing luminescent nitrogen-vacancy (NV) centers using the luminescence intensity only. We also revise the basic photo physical properties of NV centers and conclude that the luminescence quantum yield of such centers is significantly smaller than the frequently stated 100%. The yield can be as low as 5% for centers embedded in nanocrystals and depends on their shape and the refractive index of the surrounding medium. The paper also addresses the value of the absorption cross-section of NV centers. [ABSTRACT FROM AUTHOR]