Total Absorption Cross Section Research Articles

Analysis of high-frequency limit in absorption cross-section for Kerr–Newman–de Sitter black hole

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.

Quasinormal modes, temperatures and greybody factors of black holes in a generalized Rastall gravity theory

We introduce a modification in the energy-momentum conservation violating Rastall’s theory of gravity and obtain a Reissner-Nordström-type black hole solution in spacetime surrounded by a cloud of strings and charge fields. We examine the horizons of the black hole along with the influence of the parameters of the model on it. The scalar quasinormal modes (QNMs) of oscillations of the black hole are also computed using the 6th order WKB approximation method. It is seen that the Rastall parameter β and the newly introduced energy-momentum tensor trace parameter α as well as the charge parameter q and strings field parameter a influence the amplitude and damping of the QNMs. From the metric function, we obtain the temperature of the black hole and study the effects of the four model parameters β, α, q and a on the temperature. We then examine the greybody factors associated with the black hole and the corresponding total absorption cross-section for it. It is seen that the modification we introduced in the Rastall theory has a drastic effect on various properties of the black hole and may lead to interesting outcomes in future when better detection techniques will be available with the LISA and the Einstein Telescope.

Collisions of low- to intermediate-energy electrons with acetonitrile

A systematic investigation was carried out on the elastic scattering of low- to intermediate-energy electrons ( = 0.1–1000 eV eV) by acetonitrile (CH3CN). We calculated differential (DCS), integral (ICS), momentum-transfer (MTCS), and total absorption cross sections from 0.1 to 1000 eV energy range using an absorption-effects-implemented ePolyScat-E3 suite of codes, which applies the Schwinger variational method combined with the Padé-approximants technique. Also, the screen-corrected independent atom model was used to compute DCSs, ICSs, and MTCSs from 10–1000 eV impact energies. Present results are compared to other theoretical and experimental data when available. In general, our DCS and MTCS results show a good agreement with available data, however, the ICSs and the resonance features exhibit fair accordance. Our results show two shape-resonance structures: one at about 3.4 eV and a second at about 7 eV. They are labeled as and , and comprise the and scattering channels, respectively.

Absorption and scattering of a high dimensional non-commutative black hole

In this work, we investigate the scattering of massless plane scalar waves by the high dimensional non-commutative Schwarzschild–Tangherlini black hole. We use the partial wave approach to determine the scattering and absorption cross sections in the incident wavelength range. Our numerical results demonstrate that the bigger the non-commutative parameter, the smaller the maximum value of the related partial absorption cross section, however the tendency is slightly. We also discovered that when the non-commutative parameter is weak, the absorption cross section of the high dimensional black hole oscillates in the low frequency zone. The total absorption cross section oscillates around the geometrical optical limit in the high frequency range, and the scattering characteristics of black holes with various parameters are visibly different. The influence on the differential scattering cross section is particularly pronounced at large angles.

Absorption and scattering of massless scalar wave from Regular Black Holes

In this work, we numerically investigate the scattering and absorption cross section of the massless scalar field from some well-known regular black holes by using the partial wave approach. Our computational results indicate that the larger the parameters, the lower the associated total absorption cross section maxima. When compared to the Schwarzschild black hole, the scattering cross section is enhanced in some regular black hole spacetimes, meanwhile the scattering width is narrow in the forward orientation. Moreover, it is found that the null geodesics of the critical impact parameter and the geometrical optical value in the high frequency regime have similar changing behavior.

Quantum corrections to the quasinormal modes of the Schwarzschild black hole

Based on the minimum measurable momentum concepts associated with the quantum gravity effects acting on the large-scale dynamics of the universe, we study the quantum effect of the EUP on the Hawking evaporation of the black hole. The results show the quantum corrections may shorten the lifetime of the massive black hole. To verify the new EUP on the black hole stability, the scalar field and electromagnetic field are derived and the time evolution of the black hole is analyzed in terms of the time domain integration method, the quantum effect alters the oscillation and decay time of black hole. Furthermore, we use the WKB numerical approximation method to calculate the quasinormal mode frequencies and analyze the influence of the EUP parameter $$\alpha $$ on the scattering problem. This shows that the EUP significantly increases the area of the total absorption cross-section of the black hole.

Investigations on Lanthanide polymers for radiation shielding purpose

The current study involves the X-ray/gamma and neutron/EMI shielding and change in mechanical properties of selected lanthanide polymers such as Lanthanum polymer, Cerium polymer, Praseodymium polymer, Gadolinium texaphyrin polymer, Terbium co-ordination polymer and Erbium phosphate hydrate polymer. The X-ray/gamma, neutron and EMI shielding parameters are studied in detail for all the selected polymers. Among all the selected polymers, Erbium phosphate hydrate polymer shows larger values of mass attenuation coefficient, absorption buildup factor, Zeff, Ne, specific absorbed fractions of energy, radiation protection efficiency, kinetic energy released in matter, relative dose, neutron total interaction cross section and absorption cross section values. Furthermore, the EMI shielding parameter (total shielding effectiveness) was also found to be larger for Erbium phosphate hydrate polymer in near infrared, mid infrared, far infrared, ultra high frequency (UHF), very high frequency, high frequency radio waves, middle frequency radio waves, low frequency radio waves and very low frequency radio waves. This clearly indicates that Erbium phosphate hydrate polymer might be used as a good shielding material for X-ray/gamma, neutrons and EMI radiations. We have also reported the change in mechanical properties of the studied lanthanide polymers due to the interaction with X-rays/gamma rays. The mechanical properties remains unchanged in the region where pair production and photoelectric effect dominates. Change in the mechanical properties is observed in the region where Compton scattering dominates, indicating that the change in mechanical properties due to interaction of radiation is also an important parameter while selecting the shielding materials. Present study may be useful in the selection of new shielding material.

Quasinormal modes and absorption of a massless scalar field for the magnetic Gauss–Bonnet black hole

We study the massless scalar quasinormal frequencies of an asymptotically flat static and spherically symmetric black hole with a nonzero magnetic charge in four-dimensional extended scalar-tensor-Gauss–Bonnet theory. The results show that the real part of the quasinormal frequency becomes larger and the imaginary part becomes smaller with increasing the magnetic charge or the angular harmonic index. The existence of magnetic charges will reduce the damping of scalar perturbation, but increase the frequency. We also study the absorption cross-section of the scalar field in this black hole. We find that its curve will become lower as the magnetic charge increases, i.e. the magnetic charge will weaken the absorption capacity of the black hole. Meanwhile, the high-frequency limit of the total absorption cross-section is just the area of black hole shadow.

Scattering and absorption of a scalar field impinging on a charged black hole in the Einstein-Maxwell-dilaton theory

This study revisits the absorption and scattering process by which a massless scalar field impinges on a charged-dilatonic black hole. First, we review the classical analysis to obtain the deflection angle and the differential scattering cross section in terms of the mass, electric charge and dilatonic charge. Then, using the partial wave method, we determine the total absorption cross section numerically in terms of the decoupling parameter called $M\ensuremath{\omega}$, finding that the amplitude of the dilatonic black hole is lower than the Reissner-Nordstr\"om one for mild frequencies. In the high-frequency limit, the absorption cross section exhibits two different complex behaviors; the fine structure and the hyperfine structure. For the differential scattering cross section, smaller values of $M\ensuremath{\omega}$ lead to more significant amplitudes; the opposite scenario is obtained by increasing the charge-to-mass ratio. To fully grasp the main properties of the charged dilatonic black hole, we consider a different framework where the compact object is impinged by a charged massive scalar field. The superradiant effect is lessened for intermediate frequency concerning the Reissner-Nordstr\"om case. However, this effect does not necessarily imply the existence of any dynamical instability. In order to trigger the superradiant instability, unstable modes must remain trapped outside the event horizon with a mechanism based on the reflecting-mirror boundary conditions. In this way, a charged scalar field plus a charged black hole configure a charged black hole bomb. We provide an analytic formula (lower bound) for the values of the charge field, which can trigger this superradiant instability. We extend this minimal setup by considering the dilaton perturbations while freezing the other degree of freedom. The new perturbation scheme enhances the superradiance scattering and reduces the lower bound of the charge-to-mass ratio to develop a superradiant instability.

Angle-resolved line profiles in the predissociation of D2 : A summation of Fano and Lorentzian profiles

Fano profiles usually refer to the line profiles due to the total photon absorption cross sections. In this work, we measured the angle-resolved line profiles of the $\mathrm{D}(2s,2p)$ fragments from the predissociation of ${\mathrm{D}}_{2}$ near the second threshold using the D-atom Rydberg tagging time-of-flight method. The line profiles of the fragments recoiling at the parallel and perpendicular directions to the polarization direction of the excitation laser were found to be significantly different from each other, as well as with the Fano profiles of total absorption cross sections. Based on the previous theoretical results, we found that the angle-resolved line profiles can be expressed as a summation of Fano and Lorentzian profiles. Using the formula and the previously determined parameters from the so-called \ensuremath{\beta} profiles, we calculated the angle-resolved line profiles, which are in good agreement with the experimental data. Anisotropy parameters arising from the interferences between the continuum and discrete states were found to play a role in the angle-resolved line profiles.

Electron scattering cross sections for diazene (N[formula omitted]H[formula omitted]) and hydrazine (N[formula omitted]H[formula omitted

In this work, a computational study on electron interactions with diazene (N2H2) and hydrazine (N2H4) was performed; two conformations of N2H2 (E–N2H2 and Z–N2H2) were considered. Differential cross sections (DCS), integral cross sections (ICS), and momentum transfer cross sections (MTCS) for elastic scattering as well as total cross sections (TCS) and total absorption cross sections (TACS) were explored at incident energies from 0.1 to 500 eV. A molecular complex optical potential approach combined with Padé approximants was used for describing the electron–molecule collision dynamics and solving the scattering equations. Marked differences were noticed when the DCS for elastic electron–Z–N2H2 scattering were compared to the corresponding results for electron–E–N2H2 (particularly at low incident energies and small angles), a behavior which was assigned to the existence of a permanent dipole moment in the case of the Z–N2H2 molecule; results regarding N2H4 were found to be considerably more similar to those determined for Z–N2H2. In terms of ICS and MTCS, results obtained for E–N2H2 presented a first peak at 1.15 eV (originating from the 2Bg continuum symmetry and being related to the π∗ resonance arising from the nitrogen-nitrogen bond) and another at around 10 eV. These peaks can be related to the −N=N− moiety and to the existence of the N−H bonds, respectively. Interestingly, no peaks were clearly observed in Z–N2H2 ICS and MTCS while only the peak at around 10 eV was (barely) seen in the MTCS of N2H4, even without employing the Born-closure procedure. Hence, conformation plays a major role in probing the resonances for the N2H2 molecule, being the strong dipole moments responsible for masking the structures in the case of Z–N2H2 (as well as eventual additional peaks in N2H4). TACS results were found to be (practically) the same for both conformations of N2H2 at the energy range probed, being systematically lower than N2H4 TACS. In addition, the maxima of absorption was found at 70 eV for N2H4, which is slightly shifted when compared to the maxima probed for E–N2H2 and Z–N2H2 (observed at 80 eV).

Large-scale production by centrifugation of isotopically modified molybdenum for nuclear reactors and its cost evaluation

Molybdenum is considered as one of the substitutes for zirconium in making fuel cladding for safe reactor designs. The isotopically modified molybdenum (IMM) should be used instead of natural molybdenum to achieve higher energy efficiency, reduce uranium consumption, and mitigate the impact on the nuclear fuel cycle. This task can be fulfilled by using the same technology of gas centrifugation for uranium enrichment to remove the isotopes in natural molybdenum with larger thermal neutron absorption cross sections. Optimized double-cascade separation schemes consisting of the Q-cascade model are employed for studying massive production of IMM and evaluating the economic feasibility of production. A simple formula is derived to be able to assess the cost per kilogram of IMM, taking into account various cost-affecting factors. The results demonstrate that it is feasible to produce massively the IMM with a total thermal neutron absorption cross section equivalent to that of zirconium.

Gamma and neutron attenuation characteristics of bricks containing zinc extraction residue as a novel shielding material

In recent years, people are exposed to radiation depending on the technology developed which may cause serious incurable health problems. To protect from radiation exposure, various radiation shielding materials are used in different areas. In this study, zinc extraction residue (ZER), which is released during zinc production containing various heavy metals, was evaluated in clay-based brick manufacturing. The fired bricks were characterized in terms of radiation shielding, bulk density and compressive strength. Clay brick with 50% ZER was fired at 1000 °C. Bulk density and compressive strength of fired brick were found as 2.16 g/cm3 and 12.6 MPa, respectively. The addition of ZER increased the density while reducing the compressive strength. Radiation shielding potential for the samples were evaluated both experimentally (using an Am–Be neutron source and a Cs-137 gamma source) and simulation-wise using the Monte Carlo technique. For this purpose, mass attenuation coefficients of gammas and total absorption cross-section of neutrons were determined through measurements. Additionally, Monte Carlo simulations were carried out under similar irradiation conditions. The MCNP simulation results were checked against those produced from XCOM database for photons and Phy-X/PSD for neutrons. Inclusion of ZER was found to elevate shielding capabilities especially at low photon energies because of the lead content of ZER. In addition, neutron attenuation characteristics of ZER bricks were observed to be relatively lower than that of fired clay brick because of the heavier ingredients existing in ZER extracts.

Investigation on shielding properties of lead based alloys

The current study involves the X-ray/gamma and neutron shielding properties of selected lead based binary/tertiary/quaternary alloys such as Foundary type, Lino type, Molybdochalkos, Mono type, Stereo type, Turne type, Type metal and Woods metal. The X-ray/gamma and neutron shielding parameters are studied in detail for all the selected alloys. Among all the selected alloys, Molybdochalkos shows larger values of mass attenuation coefficient (MAC), absorption buildup factor (ABF), Zeff, Ne, specific absorbed fractions of energy (SAFE), radiation protection efficiency (RPE), kinetic energy released in matter (KERMA) and relative dose. Furthermore, neutron total interaction cross section (σtot) and absorption cross section (σab) values are also larger. This clearly indicates that Molybdochalkos binary alloy is the good absorber of both X-ray/gamma and neutrons.

Physical, structural and optical characterization of Dy3+ doped ZnF2-WO2-B2O3-TeO2 glasses for opto-communication applications

Abstract A series of ZnF2-WO2-B2O3-TeO2 (ZWFBT) glasses doped with different concentration of Dy3+ ions were prepared by using the melt quench method. The non-crystalline behavior of as-quenched ZWFBTDy glasses was approved by XRD spectra. The presence of different functional groups were identified by monitoring FT-IR spectra of ZWFBTDy glasses. The Differential Scanning Calorimetry (DSC) was used to estimate glass transition temperature (Tg) and thermal stability (ΔT) of an un-doped glass along with doped glasses. Physical parameters were estimated for Dy3+ doped ZWFBT glasses by using the formula available in the literature. The energy band gaps of as-quenched ZWFBTDy glasses were estimated by using three different theoretical models such as Mott and Davis relation, Hydrogenic Excitonic Model (HEM), and Urbach analysis. The optical absorption spectra were used to estimate the bonding parameters (δ) for elucidating the kind of bonding amide Dy3+ ions and its nearby ligands in the as-quenched glasses. The obtained experimental data from optical absorption spectra were compared with theoretical data calculated in the ambit of the Judd-Ofelt (J-O) theory. The J-O intensity parameters were estimated and a similar trend was observed ( Ω 2 > Ω 6 > Ω 4 ) for the as-prepared ZWFBTDy glasses. The results obtained using J-O intensity parameters are found consistent with the bonding parameters. The radiative parameters such as branching ratio, radiative transition, radiative lifetime, total radiative transition, absorption, and emission cross-sections were evaluated and discussed. The gain coefficient was evaluated for the NIR transitions of as-quenched ZWFBTDy glasses. The obtained results suggested that the as-prepared ZWFBTDy glasses were auspicious candidates for laser emission and optical communication applications.

Electron interactions with C2H6O2 isomers

In this work, a theoretical investigation on the electron interactions with the C2H6O2 isomers ethylene glycol (ETG) and dimethyl peroxide (DMP) is presented. Differential cross sections (DCS), integral cross sections (ICS), and momentum transfer cross sections (MTCS) for elastic scattering as well as total cross sections (TCS) and total absorption cross sections were determined in the 1–500 eV range. To describe the electron–target interaction and solve the scattering equations, a molecular complex optical potential (MCOP) approach combined with the Padé approximant technique was employed. Regarding ICS results, the resonance found at around 10 eV in previous investigations for electron scattering with ethanol and dimethyl ether was also detected for both molecules studied in this work. Interestingly, DMP exhibited an additional resonance feature at around 5 eV. This resonance (that can also be observed in the MTCS and TCS results for DMP) was assigned to the O−O single bond, having σ∗ character and being related to the Bu scattering symmetry. This work is presented to encourage other investigations involving ETG and DMP.

Preparation of boron carbide nanosheets with high neutron-shielding properties based on reduced graphene oxide aerogel

For this paper, boron carbide nanosheets were synthesized using a simple solid-phase thermal reaction with reduced graphene oxide (rGO) aerogel as a carbon source and amorphous boron powder as a boron source. The phase, structure, morphology, and particle size of the prepared B4C were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nanoparticle size distribution analysis. The effect of the reaction temperature, reaction time and B/C molar ratio on the crystal structure of B4C were also investigated. The results showed that the optimum conditions for the synthesis of B4C nanosheets were a reaction temperature of 1450 °C, a reaction time of 4 h and a B/C molar ratio of 4. The resulting nanosheets are hexagonal in shape, with edge lengths of 200–500 nm and an average thickness of about 100 nm. The crystal structure of the nanosheet is rhombohedral. The formation mechanism of the nanosheets is discussed on the basis of the experimental results. In addition, testing the neutron-shielding properties of the B4C composites showed that neutron transmittance with a B4C nanosheets content of 25 wt% was 94.83% lower (from 56.47% to 2.92%) than with epoxy resin, and the total macroscopic absorption cross-section was 518.41% greater (from 0.2857 ± 0.0023 cm−1 to 1.7668 ± 0.0004 cm−1). Hence, the results of this study identify a lightweight, effective material with excellent neutron-shielding properties.

A quantum wavepacket study of state-to-state photodissociation dynamics of HOBr/DOBr

Photodissociation of HOBr is an important step in the reaction network of the depletion of ozone in stratosphere. Here, we report the first three-dimensional potential energy surfaces for the lowest three singlet states for HOBr, based on high level multi reference configuration interaction calculations. Quantum dynamics calculations are performed with a real wavepacket method, yielding not only absorption spectra but also internal state and angular distributions of the photodissociation fragments. Our results agree quantitatively with the measured total absorption cross sections of HOBr in the ultraviolet region and reproduce well the observed vibrationally cold and rotationally hot OH/OD fragments via photodissociation of HOBr/DOBr at 266 nm. In addition, we predict that the recoil anisotropy parameters for OH/OD are close to the limiting value of a parallel transition, suggesting a rapid dissociation process at 266 nm following an in-plane transition from the ground state (11A′) to the 21A′ state. This is consistent with the experimental conclusion derived from the measured rotational alignment. However, spin and electronic angular momenta need to be taken into account in the future to achieve a more quantitative agreement with experiment. Our work is expected to motivate further experimental investigations for this benchmark system.

Polarization-Independent Reconfigurable Graphene Gas Sensor Using Crescent Plasmonic Antenna

A polarization-independent gas sensor based on crescent plasmonic dipole antenna loaded with graphene monolayer is introduced in this paper for environment monitoring applications. Single, dual, and four arms crescent dipoles are designed, analyzed and investigated. The proposed gas sensor has reconfigurable absorption characteristics in the wavelength range from 900 to 1600 nm which covers the different gases responses. A parametric study on the effect of the sensor dimensions and polarization of the illuminated waves on the total absorption of different gases is investigated. A graphene monolayer is used to enhance the gas molecule absorption in its unbiased state. An enhancement of the total absorption cross section (ACS) values for n = 1.4 is 1.028 × 105 nm2 for the unloaded sensor case and is 1.77 × 105 for the graphene loaded sensor case. The unloaded graphene sensor sensitivity is 630 nm/RIU, and for the graphene loaded case is 677.5 nm/RIU. Dual-polarized crescent dipole consists of two orthogonal arms is designed to maintain the same sensitivity for x- and y-polarized E-field illumination. A polarization independent gas sensor consists of four crescents dipole arms rotated with 45° is explained. An enhancement of gas absorption is achieved by using a sensor array of four-arm dipole sensor. Different array sizes loaded with graphene monolayer are investigated. The total ACS peak value is 7.84 × 106 nm2 for 6 × 6 dipole array is obtained.

Local Heating Control of Plasmonic Nanoparticles for Different Incident Lights and Nanoparticles

This paper investigates the nanoscale control of heating processes in the Au nanostructures from the aspects of light sources, nanoparticle morphologies, multi-layer Au shells, and nanoparticle dimers. The spatiotemporal evolution of the temperature profile inside and around the Au nanoparticles is computed using a numerical framework based on the finite element method. One-temperature model and two-temperature model are used for the calculation of continuous-wave and picosecond pulse laser, respectively. Results show that the maximum temperature increase is linear with the laser energy density, the slopes of which are various for continuous-wave laser and picosecond pulse laser. For the Au cube, ellipsoid, ring, and sphere with the same volume, the maximum resonance wavelengths locate in ~ 580 nm, 610 nm, 500 nm, and 530 nm, respectively. The trend of the maximum temperature increase agrees well with the absorption cross section. With increasing the number of the shell, a red shift occurs from 665 to 690 nm and the total absorption cross section also increases. What needs to be emphasized is that it does not need to heat the surrounding environment while the core region remains a very high temperature, which is very interesting and suitable for photothermal applications such as photothermal catalysis and nanoreaction oven. For the nanoshell dimers, it can be heated selectively by adjusting the incident angle and light wavelength for this dimer system.