Total Scattering Cross Section Research Articles

Superscattering of light: fundamentals and applications.

Superscattering, theoretically predicted in 2010 and experimentally observed in 2019, is an exotic scattering phenomenon of light from subwavelength nanostructures. In principle, superscattering allows for an arbitrarily large total scattering cross section, due to the degenerate resonance of eigenmodes or channels. Consequently, the total scattering cross section of a superscatterer can be significantly enhanced, far exceeding the so-called single-channel limit. Superscattering offers a unique avenue for enhancing light-matter interactions and can enable numerous practical applications, ranging from sensing, light trapping, bioimaging, and communications to optoelectronics. This paper provides a comprehensive review of the recent progress and developments in the superscattering of light, with a specific focus on elucidating its theoretical origins, experimental observations, and manipulations. Moreover, we offer an outlook on future research directions in superscattering, including potential realizations of directional superscattering, scattering-free plasmonic superscattering, enhancement of free-electron radiation and the Purcell effect via superscatterers, inelastic superscattering, and superscattering of non-electromagnetic waves.

CVAE-Based Inverse Design of Two-Dimensional Honeycomb Pentamode Metastructure for Acoustic Cloaking

In this work, a method for inverse design of two-dimensional honeycomb pentamode metastructures (HPM) based on the Conditional Variational Auto-Encoder (CVAE) is proposed to achieve acoustic cloaking. The parameter distribution of the perfect acoustic cloak with two-dimensional cylindrical Kohn-Shen-Vogelius-Weinstein (KSVW) mapping is first derived. The CVAE model framework is then established along with its loss function in terms of the design parameters of the HPM. The inverse design performance of the deep generative model is evaluated using a large number of random test samples based on finite element simulations, showing that the equivalent mechanical parameters obtained from inverse design are highly consistent with the target parameters of the perfect acoustic cloak. For the HPM cloak design given by the trained deep generative model, the total scattering cross section (TSCS) is significantly reduced as compared to the case without a cloak, thereby demonstrating the effectiveness of the CVAE-based inverse design of acoustic cloak.

Charged current weak production of Δ(1232) induced by electrons and positrons

The charged current weak production of Δ(1232) from the free proton target induced by the electron/positron in the intermediate energy range corresponding to the beam energy available at JLab and Mainz, has been studied. The results for the differential scattering cross section dσdQ2, the angular distribution dσdΩΔ, and the total scattering cross section σ(Ee) for both the electron and positron induced processes are presented, for the various energies in the range of 0.5–4 GeV. The cross section σ(Ee) is found to be of the order of 10−39 cm2 for the electron/positron energies in the few GeV range. The availability of electron/positron beams having well-defined energy and direction with very high luminosity of the order of 1038–1039 cm−2 sec−1, makes it possible to observe the weak charged current production of Δ(1232) and determine the axial vector form factors CiA(Q2);(i=3–5). The sensitivity of the differential cross section dσdQ2 to the subdominant form factors C3A(Q2) and C4A(Q2) is found to be strong enough, especially in the low Q2 region, which can be used to determine them phenomenologically and to test the various theoretical models proposed to calculate them. Published by the American Physical Society 2024

Investigation of the impact of thermal neutron scattering cross sections and angular distributions on criticality calculations

The present study focuses on the influence of neutron scattering cross section and angular distribution when employing the Thermal Scattering Law (TSL) on criticality calculation benchmarks, in comparison with the Free Gas Model (FGM). The benchmarks sensitive to beryllium oxide (HMT-027) and graphite (HMT-026) as well as some simplified Pressurized Water Reactor (PWR) benchmarks are interpreted using the OpenMC code to assess the influence of TSL. The results indicate that the influence of TSL mainly attributes to both the total scattering cross section and the secondary angular distribution characterized by the average cosine of the scattering angle. The HMT-027 and HMT-026 series benchmarks respectively show the more significant influence of one of these two effects. For the simplified PWR benchmark, employing the TSL of H in H2O weakens the neutron moderation effect, which results in a reduction of around 100 pcm in the calculated keff, while the combined influence of cross section and secondary angular distribution is negligible for the TSL of UO2 fuel.

Superscattering engineering through combined resonant modes

Abstract A sub-wavelength particle with a total scattering cross section that exceeds the single channel limit is referred to as a superscatterer, which can provide ability to control light in nanoscale. A variety of superscatter structures have been suggested, most of them are typically constructed with strong forward scattering but minor backscattering. This unusual behavior can be attributed to the superposition of resonant modes in adjacent angular momentum channels. We reveal the mechanism of super backscattering for subwavelength column, which can be formed by recombining non-adjacent resonant modes, as confirmed by our numerical analysis.

Quantum motion of oxygen and hydrogen in water: Atomic and total kinetic energy across melting from neutron scattering measurements.

We provide a concurrent measurement of the hydrogen and oxygen nuclear kinetic energies in the water molecule across melting at 270K in the solid phase and 276K in the liquid phase. Experimental values are obtained by analyzing the neutron Compton profiles of each atomic species in a deep inelastic neutron scattering experiment. The concurrent measurement of the atom kinetic energy of both hydrogen and oxygen allows the estimate of the total kinetic energy per molecule due to the motion of nuclei, specifically 35.3 ± 0.8 and 34.8 ± 0.8kJ/mol for the solid and liquid phases, respectively. Such a small difference supports results from abinitio simulations and phenomenological models from the literature on the mechanism of competing quantum effects across the phase change. Despite the experimental uncertainties, the results are consistent with the trend from state-of-the-art computer simulations, whereby the atom and molecule kinetic energies in the liquid phase would be slightly lower than in the solid phase. Moreover, the small change of nuclear kinetic energy across melting can be used to simplify the calculation of neutron-related environmental dose in complex locations, such as high altitude or polar neutron radiation research stations where liquid water and ice are both present: for neutron energies between hundreds of meV and tens of keV, the total scattering cross section per molecule in the two phases can be considered the same, with the macroscopic cross section only depending upon the density changes of water near the melting point.

Using Thin Films of Phase-Change Material for Active Tuning of Terahertz Waves Scattering on Dielectric Cylinders.

The scattering of electromagnetic waves by isotropic dielectric cylinders can be dramatically modified by means of vanadium dioxide (VO2) thin-film coatings. Efficient dynamic control of scattering is achieved due to the variations in material parameters realizable by means of external biasing. In this paper, we study the scattering of terahertz waves in a case where the coating shells are made of VO2, a phase-change material, whose thin films may work rather as electromagnetic phase screens in the insulator material phase, but as lossy quasi-metallic components in the metallic material phase. The shells that uniformly cover the dielectric cylinders are investigated. Attention will be paid to the demonstration of the potential of VO2 in the external control of diverse scattering regimes of the dielectric-VO2 core-shell scatterer, while conductivity of VO2 corresponds to rather insignificant variations in temperature. In line with the purposes of this work, it is shown that the different resonant and nonresonant regimes have different sensitivity to the variations in VO2 conductivity. Both the total scattering cross section and field distributions inside and around the core are studied, as well as the angle-dependent scattering cross section.

Total and Double Differential Scattering Cross-Section Measurements of Isotropic Graphite

Total and Double Differential Scattering Cross-Section Measurements of Isotropic Graphite

Neural Network Predictions of Atomic Form Factors and Incoherent Scattering Functions

In order to predict atomic form factors and incoherent scattering functions which are used to calculate the coherent and incoherent total scattering cross sections, a technique based on artificial neural networks of the multilayer type was implemented. In this context, two neural models have been developed and compared with those in the literature. This study revealed both the accuracy of the results obtained and the effectiveness of the designed model. The mean relative error for the least estimated property does not exceed 16.5 %. The software realized in this way give a prediction of the above parameters for the input variables Z: Atomic number, x: sin(ϑ/2)/λ and E: Photon energy, and it provides users with flexibility for prediction. The advantages of this technique lie in its very fast handling, due to its ease of use, and in the two integrated networks, which it guarantees for a variety of input parameters such as atomic number, photon energy, and momentum transfer variable.

Phase function metod for elastic nucleon-nucleon scattering using Hellmann plus Coulomb potential

The phase function method/variable phase approach to potential scattering is exploited to calculate the phase shifts for nucleon-nucleon systems in low and intermediate energy regions by representing nuclear part of the interaction by the Hellmann potential while the electromagnetic part by the Coulomb one. In addition, the differential and total scattering cross sections are estimated with our phase parameters. Results reproduced by the concerned potential are in good agreement with the previous works in the literature.

Nucleon-Nucleon Elastic Scattering for Motion in The Shifted Deng-Fan Potential

The scattering theory's main objective is to comprehend an object by hurling something at it. One can learn details about an object by observing how it bounces off other objects. The potential that exists between the two particles is the thing that one seeks to comprehend. In time-independent approach to scattering, one assumes that the incident beam has been activated for a very long time and that the entire system is in a stationary state. For short-range local potentials, the variable phase methodology is highly useful in solving quantum mechanical scattering problems. Variable phase methodology/phase-function technique has been explicitly utilized for non-relativistic nucleon-nucleon scattering phenomenon with the fundamental central local potential term and without spin-orbit force. Working under this methodology, scattering phase shifts, total scattering cross section and Differential cross section have been investigated for a new nuclear potential model “Shifted Deng-Fan potential”. Real nucleon-nucleon scattering systems (n-p) and (p-p) have been treated for this purpose with partial waves up to l = 2 in the low and moderate energy region. For l > 0 waves, interacting repulsive barrier potential has been incorporated with the existing central part. Our results for the considered potential model show a close contest with that of the experimental data.

Theoretical Investigation of Electron Impact Scattering on Imidazole.

This study presents the results of electron scattering calculations on a biologically important molecule, imidazole, using the UK molecular R-matrix method. The R-matrix calculations are performed using SE, SEP, and CC models, and the resonance detected in the present SEP model is found to be in better agreement with available experimental data than previous theoretical data. The study also reports an inelastic scattering cross section, which comprises dissociative electron attachment (DEA), excitation, and ionization cross section, for the first time. The total scattering cross sections are also reported for the first time. We confirm the presence of the two well-known π* shape resonances predicted earlier experimentally. Due to the scarcity of total scattering cross section (TCS) data for imidazole, we have compared the TCS of imidazole with its isoelectronic target isoxazole and drawn important conclusions. A comparison among the resonances of imidazole with those of isoxazole helps us to conclude that electron attachment to π* molecular orbitals is a general feature displayed by these five-membered heterocyclic compounds. The comprehensive electron scattering studies presented in this work are expected to provide a deeper understanding of electron-induced biochemical processes and fill gaps in the available data. Furthermore, this study is anticipated to inspire further investigations on imidazole and other five-membered heterocyclic ring molecules, which have significant applications in medicine.

Improving working volume and total scattering cross section using polarization convertor stirrer in a reverberation chamber

AbstractIn our paper, a stirrer made of a polarization converter for a reverberation chamber (RC) is proposed. A cylindrical polarization converter (PC) stirrer with two unit structures arranged alternatively is placed in RC to take the place of a traditional metallic stirrer. Because of the scattering property of the PC stirrer, it is possible to enlarge the working volume and improve the scattering performance of the stirrer in the RC while maintaining the field uniformity and field anisotropy coefficient to meet the testing standard of the International Electrotechnical Commission 61000‐4‐21. Metallic stirrer and PC stirrer are both placed in the RC simultaneously to make a measurement for guaranteeing the same testing environment. Some parameters of the RC stirred by the PC stirrer or metallic stirrer have been measured and analyzed, such as field uniformity, field anisotropy, coefficient independent sample number and total scattering cross‐section (TSCS), and so on. Testing results verify that the RC stirred by a PC stirrer outperforms the classic RC stirred by a conventional metallic stirrer in terms of some performance, indicating that the proposal has a significant impact on RC testing technology that requires a larger working volume and better TSCS.

Numerical analysis of the total scattering cross section on a set of sound-permeable spheres

One of the most important subtasks of the problem of acoustic wave scattering on a set of small spherical obstacles is to determine the main characteristic of the scattering phenomenon, namely, the total scattering cross section. Its solution will make it possible to establish at what system parameters the interaction between particles is insignificant and can be neglected (in this case, the problem can be simplified and reduced to the many single particles case), and at what parameters this interaction cannot be neglected. In present work a numerical parametric analysis of the total scattering cross section on a spheres system under the influence of a spherical wave from a monopole radiation source is carried out on the base on an explicit formula for the total scattering cross section on a set of interacting sound-permeable spheres. In order to determine the ratio of the physical parameters of the sphere and the environment, under which the effects of multiple scattering are significant for given types of system configuration, a series of computational experiments was carried out to calculate the main scattering characteristic taking into account multiple scattering, as well as the sums of characteristics for single sound-permeable spheres. It is shown that in all cases considered, the effects of multiple scattering cannot be neglected when determining the total scattering cross section. In the case of air bubbles in water, the type of configuration of the system is an essential factor; for water droplets in the air, both the type of configuration and the number of spheres in it are essential; and for dichloroethane droplets in water, the type of configuration and the number of spheres in it are insignificant factors.

Electromagnetic Wave Scattering by a Multiple Core Model of Composite Cylindrical Wires at Oblique Incidence

A complex cylindrical structure consisting of a group of parallel stratified circular lossy dielectric cylinders, embedded in a dielectric circular cylindrical region and surrounded by unbounded dielectric space, is considered in this paper. The scattering of electromagnetic (EM) plane waves by the aforementioned configuration was studied; the EM waves impinged obliquely upon the structure and were arbitrarily polarized. The formulation used was based on the boundary-value approach coupled with the generalized separation of variables method. The EM field in each region of space was expanded in cylindrical wave-functions. Furthermore, the translational addition theorem of these functions was applied in order to match the EM field components on any cylindrical interface and enforce the boundary conditions. The end result of the analysis is an infinite set of linear algebraic equations with the wave amplitudes as unknowns. The system is solved by the truncation of series and unknowns and then matrix inversion; thus, we provide a semi-analytical solution for the scattered far-field and, as a consequence, for the scattering cross section of the complex cylindrical structure. The numerical results focus on calculations of the electric- and magnetic-field intensity of the far-field as well as of the total scattering cross section of several geometric configurations that fall within the aforementioned general structure. The effect of the geometrical and electrical characteristics of the structure on the scattered field was investigated. Specifically, the cylinders’ size and spacing, their conductivity and permittivity as well as the incidence direction were modified in order to probe how these variations are imprinted on scattering. Moreover, comparisons with previously published results, as well as convergence tests, were performed; all tests and comparisons proved to be successful.

Omnidirectional acoustic cloaking against airborne sound realized by a locally resonant sonic material

We report that a locally resonant sonic material realizes omnidirectional acoustic invisibility in air. To achieve acoustic cloaking in the low-frequency regime, we axisymmetrically placed elastic rods comprised of silicone rubber and lead around a cloaked object. The radii of the rods are designed to minimize their total scattering cross section for a given frequency. The optimization is performed using an algorithm incorporating multiple scattering theory and gradient-based nonlinear programming. We numerically confirmed that the designed cloaking device suppressed the scattering cross section by almost 92% for all incident directions at the target frequency.

Coherent scattering cross sections of some rare earth compounds at small angles below [formula omitted] for 59.54 keV gamma rays

The angle integrated total scattering cross sections of some rare earth oxides were determined experimentally for 59.54 keV gamma rays in the angular ranges of 0–4°, 0–6°, 0–8°and 0–10°. From the experimental total scattering cross sections, the corresponding angle integrated incoherent scattering cross sections obtained from ENDF library (based on the nonrelativistic Hartree–Fock form factor method) was subtracted to obtain the angle integrated coherent scattering cross sections. The angle integrated coherent scattering cross sections show good agreement with that determined from ENDF data. The effective atomic numbers of the selected rare earth oxides were extracted by applying the ratio of cross section method. The variation of angle integrated coherent scattering cross section with the effective atomic number of the selected compounds have been studied.

Electron and Positron Scattering Cross Sections from CO2: A Comparative Study over a Broad Energy Range (0.1-5000 eV).

In this Review, we present a comparative study between electron and positron scattering cross sections from CO2 molecules over a broad impact energy range (0.1–5000 eV). For electron scattering, new total electron scattering cross sections (e-TCS) have been measured with a high resolution magnetically confined electron beam transmission system from 1 to 200 eV. Dissociative electron attachment processes for electron energies from 3 to 52 eV have been analyzed by measuring the relative O– anion production yield. In addition, elastic, inelastic, and total scattering cross section calculations have been carried out in the framework of the Independent Atom Model by using the Screening Corrected Additive Rule, including interference effects (IAM-SCARI). Based on the previous cross section compilation from Itikawa (J. Phys. Chem. Ref. Data, 2002, 31, 749−767) and the present measurements and calculations, an updated recommended e-TCS data set has been used as reference values to obtain a self-consistent integral cross section data set for the elastic and inelastic (vibrational excitation, electronic excitation, and ionization) scattering channels. A similar calculation has been carried out for positrons, which shows important differences between the electron scattering behavior: e.g., more relevance of the target polarization at the lower energies, more efficient excitation of the target at intermediate energies, but a lower total scattering cross section for increasing energies, even at 5000 eV. This result does not agree with the charge independence of the scattering cross section predicted by the first Born approximation (FBA). However, we have shown that the inelastic channels follow the FBA’s predictions for energies above 500 eV while the elastic part, due to the different signs of the scattering potential constituent terms, remains lower for positrons even at the maximum impact energy considered here (5000 eV). As in the case of electrons, a self-consistent set of integral positron scattering cross sections, including elastic and inelastic (vibrational excitation, electronic excitation, positronium formation, and ionization) channels is provided. Again, to derive these data, positron scattering total cross sections based on a previous compilation from Brunger et al. (J. Phys. Chem. Ref. Data, 2017, 46, 023102) and the present calculation have been used as reference values. Data for the main inelastic channels, i.e. direct ionization and positronium formation, derived with this procedure, show excellent agreement with the experimental results available in the literature. Inconsistencies found between different model potential calculations, both for the elastic and inelastic collision processes, suggest that new calculations using more sophisticated methods are required.

Broadband Acoustic Metamaterial Design via Machine Learning

Acoustic metamaterials are engineered microstructures with special mechanical and acoustic properties enabling exotic effects such as wave steering, focusing and cloaking. In this research, we develop a new machine learning framework for predicting optimal metastructures such as planar configurations of scatterers with specific functionalities. Specifically, we implement this framework by combining probabilistic generative modeling with deep learning and propose two models: a conditional variational autoencoder (CVAE) and a supervised variational autoencoder (SVAE) model. As an application of the method, here we design an acoustic cloak considering a minimization of total scattering cross-section (TSCS) for a set of cylindrical obstacles. We work with the sets of cylindrical objects confined in a region of space and streamline the design of configurations with minimal TSCS, demonstrating broadband cloaking effect at discrete sets of wavenumbers. After establishing the artificial neural networks that are capable of learning the TSCS based on the location of cylinders, we discuss our inverse design algorithms, combining variational autoencoders and the Gaussian process, for predicting optimal arrangements of scatterers given the TSCS. We show results for up to eight cylinders and discuss the efficiency and other advantages of the machine learning approach.

A buried piezoelectric spherical particle incident upon by plane shear waves

The dynamic electromechanical coupling in piezocomposites in response to wave propagation and scattering phenomenon is of great importance in engineering sciences, innovative technologies, and nondestructive evaluation. The present work is concerned with the scattering of shear waves by a spherical piezoelectric particle bonded to an infinitely extended isotropic elastic polymer matrix. The particle is assumed to have radial polling direction and spherically isotropic electromechanical properties. An incident shear wave propagates in the positive z-direction, while polarizes along the x-axis. The incident, scattered, and the transmitted electromechanical fields are analytically achieved by the utilization of spherical harmonics followed by the employment of the extended Frobenius series for the interior points of the particle to solve a set of four governing coupled differential equations for the displacement and the electric potentials. The set problem possesses a symmetry with respect to the xz-plane and as it will be shown the mentioned differential equations in conjunction with the particle-matrix interface conditions can be transformed into two systems of linear algebraic equations for the unknown constants which appeared in the Frobenius series. Verification is made in the special case of purely elastic isotropic particle. In the present formulation there is no restriction on the range of the frequency of the incident wave. The effect of the piezoelectric particle properties on the total scattering cross section is investigated. The dynamic stress concentration factors and the dynamic electric displacement concentration factor at the matrix-piezoelectric interface are calculated. Subsequently, the effect of the frequency of the incident wave on the maximum values of the dynamic stress concentration factors and the dynamic electric displacement concentration factor as well as their appurtenant locations are discussed and compared to those of the corresponding static cases.