Partial Absorption Cross Sections Research Articles

Quasi-normal modes, emission rate, and shadow of charged AdS black holes with perfect fluid dark matter* *Supported by the Doctoral Foundation of Zunyi Normal University of China (BS [2022] 07, QJJ-[2022]-314), and the National Natural Science Foundation of China (12265007). Additionally, S. H. Dong supported by 20230316 and 20240220-SIP-IPN, Mexico, and began this work with permission from IPN for a

In this study, we comprehensively investigated charged AdS black holes surrounded by a distinct form of dark matter. In particular, we focused on key elements including the Hawking temperature, quasi-normal modes (QNMs), emission rate, and shadow. We first calculated the Hawking temperature, thereby identifying critical values such as the critical radius and maximum temperature of the black hole, essential for determining its phase transition. Further analysis focused on the QNMs of charged AdS black holes immersed in perfect fluid dark matter (PFDM) within the massless scalar field paradigm. Employing the Wentzel-Kramers-Brillouin (WKB) method, we accurately derived the frequencies of these QNMs. Additionally, we conducted a meticulous assessment of how the intensity of the PFDM parameter α influences the partial absorption cross sections of the black hole, along with a detailed study of the frequency variation of the energy emission rate. The pivotal role of geodesics in understanding astrophysical black hole characteristics is highlighted. Specifically, we examined the influence of the dark matter parameter on photon evolution by computing the shadow radius of the black hole. Our findings distinctly demonstrate the significant impact of the PFDM parameter α on the boundaries of this shadow, providing crucial insights into its features and interactions. We also provide profound insights into the intricate dynamics between a charged AdS black hole, novel dark matter, and various physical phenomena, elucidating their interplay and contributing valuable knowledge to the understanding of these cosmic entities.

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.

Photo response of Dy164

Background: Little data is available for the pygmy dipole resonance (PDR) in axially deformed nuclei. Photon-scattering experiments are complicated by high level densities in the PDR region and the small energy difference of transitions to the ground state and to excited states.Purpose: We report on an experimental study of the low-energy dipole strength distribution of the well-deformed nucleus $^{164}\mathrm{Dy}$ between 4.0--7.7 MeV.Methods: The low-lying photoresponse of $^{164}\mathrm{Dy}$ has been investigated using the method of nuclear resonance fluorescence using a quasimonochromatic linearly polarized $\ensuremath{\gamma}$-ray beam in the energy range of 4.0--7.7 MeV in steps of 0.2 MeV.Results: For excitation energies between 4 MeV and 5 MeV, sufficiently low level densities allow for the identification of individual states, including level energies, reduced transition widths and branching ratios. Energy-averaged mean decay branching ratios, mean population ratios and partial absorption cross sections were determined above 5 MeV up to the neutron-separation threshold at 7.7 MeV. A Lorentzian-shaped enhancement of the partial photo absorption cross section followed by decays back to the ground-state band is found at 6.10(5) MeV with a width of 0.77(23) MeV. A comparison with results from complementary measurements is performed using the framework of the statistical model.Conclusions: The experimental results for the mean population ratios deviate systematically from the statistical model simulation by 30(6)%. However, they are in agreement within one standard deviation of the simulation.

Massive and charged scalar field in Kerr-Newman spacetime: Absorption and superradiance

We consider the propagation of a generic scalar field around a rotating and charged black hole. Using the partial wave method, we find, numerically, the total and partial absorption cross sections for different incidence angles. We investigate the low- and high-frequency limits, finding semi-analytical approximations for the absorption cross section, which we compare with our numerical results. Finally, we consider the superradiant regime, showing that, for charged fields, planar waves can be superradiantly scattered.

Absorption of planar waves in conformal gravity space–time

Conformal gravity (CG) has attracted considerable interest as a compelling alternative to general relativity. We investigate the massless scalar planar wave scattering in Mannheim–Kazanas (MK) space–time of CG theory. We give different transmission coefficient as parameter $$\gamma r_0$$ and $$\kappa r_0^2$$ changed. Using partial-wave method, we obtain the absorption cross section, we find for larger angular momentum quantum numbers l, the corresponding maximum values of partial absorption cross section are smaller, the smaller of $$\gamma r_0$$ are, the larger the partial absorption cross section are, while parameter $$\kappa r_0^2$$ display the inverse situation.

Ultimate Absorption in Light Scattering by a Finite Obstacle.

Based on fundamental properties of the light scattering by a particle under a plane, linearly polarized wave illumination, we rigorously prove the existence of the ultimate upper limit for the light absorption by any partial mode and calculate this limit explicitly. The limit is a certain simple universal function of the incident light wave number, and the multipolarity of the corresponding partial mode solely. It does not depend on the optical constants of the scatterer, its size, or even its shape. First, we obtain this result for the scattering by a spherical particle. Then, we generalize it to an arbitrary finite obstacle. The results are valid for any polarization of the incident wave, any angle of its incidence, and any type of the scatterer (homogeneous, stratified, or with smoothly variable refractive index). We also prove that the maximal partial absorption cross section for any finite scatterer cannot exceed the corresponding value for a homogeneous sphere in 3D and circular cylinder in 2D. As an example, the results are applied to maximize the absorption cross section of a spherical core-shell structure.

Absorption cross section and Hawking radiation from Bardeen regular black hole

By using the partial wave method, we investigate the absorption of Dirac field from the Bardeen regular black hole. We numerically carry out the absorption cross section, we find that the larger angular momentum quantum numbers $$l$$ are, the smaller the corresponding maximum values of partial absorption cross section are. When the magnetic monopole charge $$\beta $$ increases, the absorption cross section and the power emission spectra of Hawking radiation increase, but the absorption probability and the luminosity decrease.

Absorption and Scattering Cross Section of Regular Black Holes

By using the partial wave method, we investigate the absorption of massless scalar wave from regular black hole. We numerically carry out the absorption cross section and find that the larger angular momentum quantum number l is, the smaller the corresponding maximum value of partial absorption cross section is. Comparing with Schwarzschild case, the absorption cross section of regular black holes is strengthened in both low and high frequency regions, and the absorption cross section oscillates around the geometric optical value in the high frequency region. Generally speaking, the scattering flux is strengthened and its scattering width becomes narrower in the forward direction. There are obvious contrast of scattering properties of different type of regular black hole.

Ozone Photodissociation: Isotopic and Electronic Branching Ratios for Symmetric and Asymmetric Isotopologues

We present new calculations of the branching ratios between the various electronic and isotopic photodissociation channels of ozone. Special emphasis is placed on the isotopic/isotopologue differences because the contribution of the ozone photodissociation to the oxygen isotope and ozone isotopologue enrichments or fractionations is important for atmospheric applications. These branching ratios, which depend on photon energy, have been calculated with a full quantum mechanical wavepacket propagation approach: the multiconfiguration time-dependent Hartree (MCTDH) method. Five ozone isotopologues are considered: three symmetric, (16)O(3) (noted 666), (16)O(17)O(16)O (676), and (16)O(18)O(16)O (686); two asymmetric, (16)O(2)(17)O (noted 667) and (16)O(2)(18)O (668). The 668 and 667 asymmetric isotopologues can dissociate into either 66 + 8 or 68 + 6 for 668 and into 66 + 7 or 67 + 6 for 667. In the ranges of the Chappuis and Hartley bands, the dissociation is very fast and electronic and isotopic branching ratios are obtained from the wavepacket fluxes through complex absorbing potentials (CAPs) located perpendicular to the dissociation channels of the potential energy surfaces (PESs) of the A (1)B(1) (Chappuis) and B 3(1)A' (Hartley/Huggins) electronic states. In the range of the Huggins band the dissociation is much slower and the isotopic branching ratios of 667 and 668 asymmetric isotopologues, (e.g; 668 → 66 + 8 or 86 + 6) are obtained from the ratios of two partial absorption cross sections corresponding to the selective excitation of one or the other of the two isomers of C(s) symmetry, which dissociate respectively into 66 + 8 and 86 + 6. We find that the photodissociation of the 668 asymmetric isotopologue favors the 68 + 6 channel with a propensity varying between 52% (Hartley) and 54% (Huggins) as a function of the photon energy. The electronic branching ratios to the singlet channel (O(3) + hυ → O((1)D) + O(2)((1)Δ)) are all close to 90% above ≈32,000 cm(-1). Below this energy, the singlet channel is energetically closed and only the triplet channel (O(3) + hυ → O((3)P) + O(2)((3)Σ)) is open. These branching ratios are required to calculate the photolysis rates of each ozone isotopologue, which in turn contribute to the atomic oxygen and the ozone isotopic enrichments in the atmosphere.

Absorption of a massless scalar wave from a Schwarzschild black hole surrounded by quintessence

By using the partial wave method, we investigate the absorption of a massless scalar wave from a Schwarzschild black hole surrounded by quintessence. We obtained the expression of absorption cross sectionThen we numerically carry out the absorption cross section and we find that the larger the angular momentum quantum number l is, the smaller the corresponding maximum value of the partial absorption cross section is, and that the total absorption cross section tends to the geometric-optical limit σhfabs ≈ πb2c. We also find that higher value of ωq (state parameter of quintessence) corresponds to the higher value of absorption cross section σabs.

Photodissociation Dynamics of 2-Bromopropane Using Velocity Map Imaging Technique

Photodissociation dynamics of 2-bromopropane in the A band was investigated at several wavelengths between 232 and 267 nm using resonance-enhanced multiphoton ionization technique combined with velocity map ion-imaging detection. The ion images of Br ((2)P(3/2)) and Br* ((2)P(1/2)) were analyzed to yield corresponding total translational energy and angular distributions. The total translational energy distributions showed that the channel leading to Br carried more internal energy in the 2-C(3)H(7) moiety than the channel leading to Br*. The anisotropy parameters of beta (Br) were obtained to be between 0.68 and 1.49, and beta (Br*) between 0.73 and 1.96, indicating that the Br* product originates from direct excitation of the (3)Q(0) state and the (1)Q(1) --> (3)Q(0) nonadiabatic transition, and the Br product from direct excitation of the (1)Q(1) or (3)Q(1) state and the (3)Q(0) --> (1)Q(1) nonadiabatic transition. The curve crossing probabilities were determined to be increase with the wavelength. As compared with the case of CH(3)Br, the two heavier branched CH(3) groups significantly enhance the Br ((2)P(3/2)) production from nonadiabatic contribution. The curve crossing from the (3)Q(0) to the (1)Q(1) surface is much higher than that of the reverse from the (1)Q(1) to the (3)Q(0) surface, which may have resulted from the difference in shape between the potential energy surfaces of the (3)Q(0) and (1)Q(1) states. Finally, based on the experimental data, the partial absorption cross sections of the A band for the (3)Q(0), (3)Q(1), and (1)Q(1) states were extracted.

Absorption Cross Section and Decay Rate of Stationary Axisymmetric Einstein–Maxwell Dilaton Axion Black Hole

The low energy absorption cross section and the decay rate of the stationary Axisymmetric Einstein–Maxwell Dilaton Axion black hole for massless scalar particles is calculated analytically. It is shown that the partial absorption cross section increases as the rotating parameter a and the absolute value of the dilaton D decreases. It is also shown that the partial absorption cross section is not always positive due to superradiance factor ω–mΩ. However, the decay rate of this black hole is always positive.

Low-Energy Absorption Cross Section for massive scalar and Dirac fermion by (4 n)-dimensional Schwarzschild Black Hole

Motivated by the brane-world scenarios, we study the absorption problem when the spacetime background is (4+n)-dimensional Schwarzschild black hole. We compute the low-energy absorption cross sections for the brane-localized massive scalar, brane-localized massive Dirac fermion, and massive bulk scalar. For the case of brane-localized massive Dirac fermion we introduce the particle's spin in the traditional Dirac form without invoking the Newman-Penrose method. Our direct introduction of spin enables us to compute contributions to the jth-level partial absorption cross section from orbital angular momenta l = j±1/2. It is shown that the contribution from the low l-level is larger than that from the high l-level in the massive case. In the massless case these two contributions are exactly same with each other. The ratio of low-energy absorption cross sections for Dirac fermion and for scalar is dependent on the number of extra dimensions as 2−(n+3)/(n+1). Thus the ratio factor 1/8 is recovered when n = 0, which Unruh found. The physical importance of this ratio factor is discussed in the context of the brane-world scenario. For the case of bulk scalar our low-energy absorption cross section for S-wave is exactly same with area of the horizon hypersurface in the massless limt, which is an higher-dimensional generaliztion of universality. Our results for all cases turn out to have correct massless and 4d limits.

Ab initio quantum mechanical investigation of the photodissociation of HI and DI

The photoabsorption spectra of HI and DI are computed using ab initio potential curves and transition dipole moments. Partial absorption cross-sections and quantum yields for the production of the ground state ( 2 P 3/2 ) and the excited spin–orbit state ( 2 P 1/2 ) of iodine are calculated using the time-dependent wave packet formalism as functions of the excitation energy. Very good overall agreement with experimental data is obtained for the band total absorption spectrum and for the I( 2 P 1/2 ) quantum yield. The spin–rotational coupling of the a 3Π 0 + and A 1Π 1 states is estimated for the first time and is shown to play a negligible role in the HI photodissociation.

Adiabatic and diabatic dynamics in the photodissociation of CH2BrCl

The photodissociation dynamics of chlorobromomethane (CBM) were investigated between 193 and 242 nm by resonance-enhanced multiphoton ionization (REMPI) with time-of-flight mass spectrometry (TOFMS). Translational energy distributions, anisotropy parameters, and Br:Br* branching ratios were determined at 193 and 235 nm to explore the non-adiabatic dynamics near the avoided crossing. Additional measurements were made at intermediate wavelengths to characterize the wavelength dependence of the Br and Br* anisotropy parameters. The non-adiabatic crossing probabilities calculated by applying a one-dimensional Landau–Zener model were relatively insensitive to the excitation wavelength, indicating that the avoided crossing between 3A′ and 4A′ potentials lies in the exit channel. Additionally, we have determined the partial absorption cross sections for the excited states that contribute to the ultraviolet absorption spectrum of CBM.

X-ray Raman scattering involving electronic continuum resonances

Theory of resonant x-ray elastic and inelastic scattering involving electronic continuum resonances is presented. As for excitation to discrete states the resonant x-ray spectral shape is found to depend strongly on the frequency of incoming photons and on the scattering angle. Contrary to excitation to discrete states, the energy scale of this dependence is defined by the finite delay time of the core-excited electron. It is shown that also the partial absorption cross sections for a continuum resonance can be obtained when the x-ray absorption spectrum is measured in the resonant inelastic x-ray scattering mode. The connection between frequency and angular dependences and the symmetries of the continuum and discrete states involved in the x-ray scattering is derived. The limiting factors for the spectral function under different circumstances are given.

Spectrometer with vertical dispersion mode for studying chemical shifts in X-ray emission lines with the use of synchrotron radiation: preliminary experiment

The spectrometer proposed uses white synchrotron radiation for fluorescence excitation. The fluorescence analysis is carried out by a double crystal diffractometer in the vertical dispersion mode. We simulate experimental data taking the uranium L α1 emission line ( ε = 13.6 keV, Δε = 11.3 eV) and Kurchatov Synchrotron Radiation Source parameters. We take into account the following parameters: the partial absorption cross section of the element under investigation μ part( ε), the SR spectral distribution, the Gaussian vertical photon angle distribution σ z′ph ( ε), and the Gaussian vertical electron linear and angle distributions σ zel and σ z′el . The emission X-ray line has been taken to have a Lorentz form. The transmission coefficient of the double crystal spectrometer in high dispersion position has been taken to have a Gauss-form σ Dar. The following results have been achieved. A measurement accuracy Δε ε ≅ 10 −6 can be achieved when measuring for ∼ 100 s with E = 2.5 GeV and I = 100 mA. Here Δε is the statistic uncertainty of the line position and ϵ is the emission line energy. The natural line width will not be increased by the spectrometer convolutions by more than 20%, so the line form can be investigated very carefully. Based on piezoelectric transducers, the diffractometer is now being commissioned. A preliminary experiment in vertical dispersion mode has been performed and fitted with the theory.

Photodissociation dynamics of jet-cooled ClNO on S1(1 1A″): An experimental study

We report measurements of photofragment yield (PHOFRY) spectra and NO E, V, R distributions following dissociation of jet-cooled ClNO on the S1(1 1A″) electronic surface. The dissociative S1(1 1A″)←S0(1 1A′) transition shows diffuse vibrational structure with a progression in ν1, the NO stretch. The absorption and PHOFRY spectra consist of two bands, corresponding to excitations into S1(000) and S1(100), whose widths are 1300±100 and 1000±70 cm−1, respectively. The relative partial absorption cross sections are S1(000):S1(100)=2.3:1.0. The narrowing of the absorption bands with increasing ν1 quanta is a consequence of the mismatch between ν1 and the free NO vibrational frequency. Dissociations on S1(000) and S1(100) yield NO in v″=0 and 1, respectively. The NO(X2∏) rotational distributions in v″=0 and 1 are inverted, peaking at J″∼30.5 with widths of 10±1 J″, and they do not vary significantly when the photolysis laser is scanned across the absorption band. The evolution of NO vibrational and rotational excitations appear to be largely uncoupled. In NO v″=0 and 1, the upper spin–orbit state 2∏3/2 is more populated than the lower state 2∏1/2. For both v″=0 and 1, the Λ-doublet ∏(A″) component of NO(2∏1/2) is more populated than the ∏(A′) component by a ratio of ∼3:1, as expected for excitation to a π* orbital of a″ symmetry, but this propensity is much lower for NO(2∏3/2), possibly due to perturbations with another surface. The absorption spectra and NO V, R distributions are in good agreement with recent dynamical calculations on a three-dimensional (3-D) potential-energy surface (PES) calculated ab initio. The vibrational distribution appears to be determined near the Franck–Condon (FC) region, while final-state interactions affect the rotational distributions at larger Cl–NO separations.

Multiple Scattering of Electrons by an Infinite Lattice Plane II. On the Properties of the Planar Scattering Matri

AbstractThe symmetry properties of both the angular momentum representation and the plane wave representation of the planar scattering matrix are derived and discussed. The generalized optical theorem is obtained from the current balance of the muffin‐tin layer. For the case without absorbing medium the absorption matrix of the muffin‐tin layer is calculated in terms of the partial absorption cross sections of the muffin‐tins.