Energy Absorption Cross Section Research Articles

Spectroscopic investigation and laser behaviour of Yb-doped laser ceramics based on mixed crystalline structure (ScxY1-x)2O3

We report on the spectroscopic and laser characterization of Yb-doped (ScxY1-x)2O3 ceramics with different Y3+/Sc3+ balance (x=0, 0.273, 0.508 and 0.742) and ~6 at.% Yb concentration, fabricated by solid-state vacuum sintering of laser-ablated mixed sesquioxide nanoparticles. The optical transmittances of 2-mm-thick samples with x=0, 0.273 and 0.508 were above 80% at a wavelength of 600 nm and 82% at 1100 nm which is very close to the theoretical limit. The lifetime of the 2F5/2 Yb3+ energy level, absorption and emission cross sections result to be influenced by the Sc3+ content. In particular, the upper state lifetime decreased from 781 μs to 614 μs with an increase in Sc2O3 concentration from 0 mol.% to 74.2 mol.%. Moreover, the main emission peaks of Yb3+ near 1040 nm and 1080 nm shift toward longer wavelength with an increase in Sc3+ content and progressively broaden until Y3+/Sc3+ balance reaches ~1. Concerning the laser tests, all samples showed good performance under quasi-CW laser diode end-pumping at 929 nm. For the mixed compositions, a maximum output power of 5.95 W with an optical-to-optical conversion efficiency of 58.8% was achieved in (Yb0.058Sc0.508Y0.434)2O3 ceramics. Most interestingly, we measured an end-to-end tuning range of 117.7 nm for the sample (Yb0.062Sc0.273Y0.665)2O3, which is to the best of our knowledge the broadest tuning range found in literature for an Yb doped laser ceramics. This represents the first highly efficient laser operation of compositionally disordered Yb-doped (ScxY1-x)2O3 ceramic matrices.

Study of total, absorption, and 3He and 3H production cross sections in 4He-proton collisions

Light ion breakup cross sections are important for studies of cosmic ray interactions in the inter-stellar medium or radiation protection considerations of energy deposition in shielding and tissues. Abrasion cross sections for heavy ion reactions have been modeled using the Glauber model in the large mass limit or Eikonal form of the optical potential model. Here we formulate an abrasion model for 4He fragmentation on protons using the Glauber model avoiding the large mass limit and include a model for final state interactions. Calculations of energy dependent total, absorption, elastic and breakup cross sections for 4He into 3He or 3H with proton targets are shown to be in good agreement with experiments for energies from 100 to 100,000 MeV/u. The Glauber model for light nuclei with and without a large mass limit approximation is shown to be in fair agreement above 300 MeV/u, however important differences occur at lower energies.

Kinetic theory of electroconductivity of metal nanoparticles in the condition of surface plasmon resonance

In recent years, there has been increasing interest in the study of the optical properties of metallic nanostructures. This interest is primarily related to the practical application of such nanostructures in quantum optical computers, micro- and nanosensors. These applications are based on the fundamental optical effect of excitation of surface plasmons. Surface plasmons are electromagnetic excitations of electron plasma of metals at the metal-dielectric interface, which are accompanied by fluctuations in the surface charge density. The consequence of this phenomenon is surface plasmon resonance (SPR) – an increase in the energy absorption cross-section of a metal nanoparticle as the light frequency (laser irradiation) approaches to the frequency of the nanoparticle SPR. The SPR frequency for metallic nanoparticles in a dielectric matrix is found. Using the kinetic subdivision, the components of the optical power tensor for ellipsoidal metal nanoparticles were developed.

Study of Doppler broadening Compton scattering and cross section determination for the elements Fe, Zn, Ag, Au and Hg

To assess the contribution of Doppler broadening and examine theCompton profile, the Compton energy absorption cross sections aremeasured and calculated using formulas based on a relativisticimpulse approximation. The Compton energy-absorption crosssections are evaluated for different elements (Fe, Zn, Ag, Au and Hg)and for a photon energy range (1 - 100 keV). With using these crosssections,the Compton component of the mass–energy absorptioncoefficient was derived, where the electron momentum prior to thescattering event caused a Doppler broadening of the Compton line.Also, the momentum resolution function was evaluated in terms ofincident and scattered photon energy and scattering angle. The resultsof cross sections for the coherent and incoherent processes arecompared with theoretical values and reported values of otherresearchers. The present results are in agreement with the theoreticalvalues.

Photoluminescence and thermoluminescence investigations of Yb:YAG nanoparticles by dual-surfactant functionalization and microwave calcination method

A novel synthesis approach is proposed to prepare strong NIR emitting Yb3+ doped YAG (Yb:YAG) nanoparticles at different Yb3+ concentrations by a modified refluxer assisted homogeneous precipitation using dual polymeric surfactant functionalization approach. Ultrafast microwave calcination has achieved Yb:YAG nanoparticles in pseudo-spherical morphology under the influence of polymeric dual SDS-PEG surfactants, evidenced from HR-TEM observation. XRD pattern of Yb:YAG nanoparticles calcined at 900 °C resulted in cubic phase formation without the evolution of YAlO3 and Y3AlO4 intermediate phases. XPS analysis revealed the presence of Yb3+ and Yb2+ mixed valence states in high-Yb doped YAG, whereas only Yb3+ is seen in moderately-Yb doped YAG nanoparticles. UV–Visible diffuse reflectance spectrum exhibit characteristic optical absorption at 940 nm is attributed to 2F7/2 → 2F5/2 electronic transitions of Yb3+ ions. From these spectral data, optical parameters such as Stark energy splitting (ΔE), absorption coefficient (α), refractive index (n) and absorption cross section (σabs) are estimated. Photoluminescence spectra of moderately (5 at%) doped Yb:YAG nanoparticles showed strong near infrared emission at 1030 nm due to Yb3+ ions that confirmed by XPS analysis. Also, the stimulated emission cross section (σem) is calculated using Fuchtbauer-Ladenburg equation. The fluorescence decay lifetime result also implies that the moderately doped YY-5S sample exhibits higher decay lifetime of 2.08 ms. In addition, present work explores the thermally stimulated luminescence properties of Yb:YAG nanoparticles for the first time by high energy γ-ray irradiation at different dose rates. TSL kinetic parameters such as structural factor (μg), order of kinetics (b), trap depth in terms of activation energy (E) and frequency factor (s) are estimated.

Lorentz invariance of absorption and extinction cross sections of a uniformly moving object

The energy absorption and energy extinction cross sections of an object in uniform translational motion in free space are Lorentz invariant, but the total energy scattering cross section is not. Indeed, the forward-scattering theorem holds true for co-moving observers but not for other inertial observers. If a pulsed plane wave with finite energy density is incident upon an object, the energies scattered, absorbed, and removed from the incident signal by the object are finite. The difference between the energy extinction cross section and the sum of the total energy scattering and energy absorption cross sections for a non-co-moving inertial observer can be either negative or positive, depending on the object's velocity, shape, size, and composition. Calculations for a uniformly translating, solid, homogeneous sphere show that all three cross sections go to zero as the sphere recedes directly from the source of the incident signal at speeds approaching c, whether the material is a plasmonic metal (e.g., silver) or simply a dissipative dielectric material (e.g., silicon carbide).

Gamma ray interaction studies of organic nonlinear optical materials in the energy range 122 keV–1330 keV

The mass attenuation coefficients (μm) for organic nonlinear optical materials measured at 122–1330keV photon energies were investigated on the basis of mixture rule and compared with obtained values of WinXCOM program. It is observed that there is a good agreement between theoretical and experimental values of the samples. All samples were irradiated with six radioactive sources such as 57Co, 133Ba, 22Na, 137Cs, 54Mn and 60Co using transmission arrangement. Effective atomic and electron numbers or electron densities (Zeff and Neff), molar extinction coefficient (ε), mass energy absorption coefficient (μen/ρ) and effective atomic energy absorption cross section (σa,en) were determined experimentally and theoretically using the obtained μm values for investigated samples and graphs have been plotted. The graph shows that the variation of all samples decreases with increasing photon energy.

Photon interaction study of organic nonlinear optical materials in the energy range 122–1330 keV

In the present study, the mass attenuation coefficient (µm) of six organic nonlinear optical materials has been calculated in the energy range 122–1330keV and compared with the obtained values from the WinXCOM program. It is found that there is a good agreement between theoretical and experimental values (<3%). The linear attenuation coefficients (µ) total atomic cross section (σt, a), and total electronic cross section (σt, el) have also been calculated from the obtained µm values and their variations with photon energy have been plotted. From the present work, it is observed that the variation of obtained values of µm, µ, σt, a, and σt, el strongly depends on the photon energy and decreases or increases due to chemical composition and density of the sample. All the samples have been studied extensively using transmission method with a view to utilize the material for radiation dosimetry. Investigated samples are good material for radiation dosimetry due their low effective atomic number. The mass attenuation coefficient (µm), linear attenuation coefficients (µ), total atomic cross section (σt, a), total electronic cross section (σt, el), effective atomic numbers (Zeff), molar extinction coefficient (ε), mass energy absorption coefficient (µen/ρ) and effective atomic energy absorption cross section (σa, en) of all sample materials have been carried out and transmission curves have been plotted. The transmission curve shows that the variation of all sample materials decreases with increasing photon energy.

Comment on: MALDI ionization mechanisms investigated by comparison of isomers of dihydroxybenzoic acid.

Ionization mechanism of matrix-assisted laser desorption/ionization was recently investigated by Kirmess et al. (J. Mass Spectrom. 2016, 51, 79). The authors compared the ion yields of dihydroxybenzoic acid isomers between experimental measurements and theoretical models and claimed that the predictions of chemical and physical dynamics model are in good agreement with experimental data, but the predictions of thermal model are not. Here, we show that wrong S1-S1 energy pooling rate constants and absorption cross sections were used in the aforementioned article. In addition, we suggest the authors to list the values of many parameters used in their calculations and describe how they obtained these values because these values are completely unknown.

Strong gravitational lensing and black hole quasinormal modes: towards a semiclassical unified description

We examine in a semiclassical framework the deflection function of strong gravitational lensing, for static and spherically symmetric black holes, endowed with a photon sphere. From a first-order WKB analysis near the maximum of the Regge-Wheeler potential, we extract the real phase shifts from the S-matrix elements and then we derive the associated semiclassical deflection function, characterized by a logarithmic divergent behavior. More precisely, using the complex angular momentum techniques, we show that the Regge poles and the associated greybody factor residues, for a massless scalar field theory, from which one can recover the black hole quasinormal complex frequencies as well as the fluctuations of the high energy absorption cross section, play naturally the role of critical parameters in the divergent behavior of the semiclassical deflection function. For very high frequencies, we finally recover the logarithmic part of the classical strong deflection limit, which clarifies analytically the fundamental link between quasinormal modes and strong gravitational lensing, suggested in recent works.

Semi-empirical relationship for the energy absorption buildup factor in some biological samples

Energy absorption buildup factors in the energy range of 0.2 MeV to 2 MeV using a geometric progression fitting approximation in some selected essential amino acids, fatty acids and carbohydrate molecules have been obtained. A semi empirical relation-ship describing energy absorption buildup factors as a function of penetration depth, Compton scattering and energy absorption cross-section is used. This semi empirical method was defined in an earlier work on water and soft tissue by one of the present authors. We used this method for the calculating energy absorption buildup factor in biological samples. The results are compared with the energy absorption buildup factors data of the geometric progression fitting method. Good agreement between semi empirical and geometric progression fitting methods has been observed, so that average deviation is less than 2 % for all samples.

ERRATUM: AN UPPER BOUND FROM HELIOSEISMOLOGY ON THE STOCHASTIC BACKGROUND OF GRAVITATIONAL WAVES (2014, ApJ, 784, 88)

We would like to point out that prior to this publication several authors have considered excitation of solar/stellar oscillations by gravitational waves. The very idea of employing the Sun as a detector for gravitational waves dates back at least to the discussion on the excitation of a 160 min solar oscillation by gravitational radiation (Walgate 1983). This discussion triggered a series of papers that refuted this speculative idea (Bonazzola et al. 1984; Kuhn & Boughn 1984; Carroll et al. 1984; Fabian & Gough 1984; Kosovichev 1984; Deruelle 1984). Furthermore, Boughn & Kuhn (1984) and, more recently, Khosroshahi & Sobouti (1997) studied the excitation of solar/stellar oscillations by gravitational waves. While Khosroshahi & Sobouti (1997) focused on computing energy absorption cross sections for polytropic models and did not report upper limits on a background of gravitational waves, Boughn & Kuhn (1984) did present such limits (as the only ones of the aforementioned authors) assuming an upper bound on the mean squared velocity of a few solar gand p-mode oscillations. The latter fact was not pointed out in the published version of this paper and we would like to correct this here. For ease of comparison, Figure 1 shows the upper limits of Boughn & Kuhn (1984) together with the upper bounds of the published paper. The upper limits presented by Boughn & Kuhn (1984) were given for individual frequencies in the range of 105.8–2116.7 Hz m . The estimate at 105.8 Hz m agrees well with our estimates around this frequency. We note that damping rates are uncertain (up to orders of magnitude) in the frequency range 110 » –1500 Hz m (cf. grey shaded area in Figure 1) and cannot be reliably calculated due to convection–pulsation interactions (Dupret 2002; Belkacem et al. 2009; Chaplin et al. 1997; Houdek 2006; Dupret et al. 2006; see also the published version of this paper). As shown by the present paper, visibility effects can influence the resulting upper bounds by The Astrophysical Journal, 810:84 (2pp), 2015 September 1 doi:10.1088/0004-637X/810/1/84

Studies on mass energy-absorption coefficients and effective atomic energy-absorption cross sections for carbohydrates

We measured here the mass attenuation coefficients (μ/ρ) of carbohydrates, Esculine (C15H16O9), Sucrose (C12H22O11), Sorbitol (C6H14O6), d-Galactose (C6H12O6), Inositol (C6H12O6), d-Xylose (C5H10O5) covering the energy range from 122 keV up to 1330 keV photon energies by using gamma ray transmission method in a narrow beam good geometry set-up. The gamma-rays were detected using NaI(Tl) scintillation detection system with a resolution of 8.2% at 662 keV. The attenuation coefficient data were then used to obtain the total attenuation cross-section (σtot), molar extinction coefficients (ε), mass-energy absorption coefficients (μen/ρ) and effective (average) atomic energy-absorption cross section (σa,en) of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.

Enhanced optical absorption and electric field resonance in diabolo metal bar optical antennas

Resonance behaviors of the fundamental resonance mode of diabolo metal bar optical antennas are investigated by using finite-difference time-domain (FDTD) numerical simulations and a dipole oscillator model. It is found that as the waist of the diabolo metal bar optical antenna is reduced, optical energy absorption cross section and near field enhancement at resonance increase significantly. Also reduction of the diabolo waist width causes red-shift of the resonant wavelengths in the spectra of absorption cross-section, scattering cross-section, and the near electric field. A dipole oscillator model including the self-inductance force is used to fit the FDTD numerical simulation results. The dipole oscillator model characterizes well the resonance behaviors of narrow waist diabolo metal bar optical antennas.

Trends in organic hydroperoxide photodissociation and absorption cross sections between 266 and 377 nm

Organic hydroperoxides have atmospheric roles in secondary organic aerosol formation and maintaining OH radical concentrations. Monitoring OH from CH3CH2OOH and (CH3)3COOH at 266, 291, 331, 362, and 377nm yields trends in energy disposal and absorption cross sections. Nascent OH radicals emerge similarly, but with less translational energy from the heavier parent. Cross sections are new for CH3CH2OOH and extend the range for (CH3)3COOH, which has implications for modeling atmospheric OH concentrations. Lower cross sections and higher OH rotation for (CH3)3COOH <331nm could be due to a higher trans barrier for torsion about the O–O bond, compared to CH3OOH and CH3CH2OOH.

Photon interaction, energy absorption and neutron removal cross section of concrete including marble

The gamma and neutron shielding properties of different types of concretes have been investigated. The effective atomic number, Zeff, and the effective electron density, Ne,eff, for photon interaction and energy absorption have been calculated for a wide range of photon energy for concrete where marble concentrations used 0%, 5%, 10%, and 20%. The macroscopic fast neutron removal cross-sections and mean free paths have also been calculated by NXcom program. The moderator effect on neutron attenuation coefficient has been discussed. Also, the transmission of neutron has been obtained as a function of thickness of concrete for all concrete types. It was found that increasing marble rate in the concrete leads to decrease of neutron removal cross section and improvement of shielding against gamma rays.

A semi-empirical approach to the geometric progression (GP) fitting approximation in estimating photon buildup factor in soft tissue, water, and dosimetric materials

Photon buildup factors for soft tissue, water, and dosimetric materials have been computed in the energy range of 0.2 to 2 MeV using geometric progression (GP) fitting approximation. The results for soft tissue and water have been compared with the values obtained through Monte Carlo code MCNP4C. Data obtained from GP fitting method quite well obey a semi empirical relation which is a function of penetration depth, Compton scattering and energy absorption cross section. With the help of this semi-empirical approximation, buildup factors for gamma and X-rays in soft tissue, water, and dosimetric materials consisting of elements Hydrogen (H), Carbon (C), Nitrogen (N) and Oxygen (O), can be easily estimated in the energy range of 0.2 to 2 MeV up to penetration depths of 10 mfp. Key words: Buildup factor, geometric progression (GP) fitting method, Monte Carlo method, radiation shielding.

Semi-empirical relationship for photon buildup factor in soft tissue and water

Buildup factor of gamma and X-ray photons in the energy range of 0.2-2 MeV in water and soft tissue is computed using Monte Carlo code MCNP4C. The results are compared with the buildup factor data of pure water. A new relationship estimating buildup factor as a function of penetration depth, Compton scattering and energy absorption cross sections is introduced. The new relationship estimates buildup factor with 5 % deviation compared with the existing data.

Absorption on horizon-wrapped branes

We compute the low energy absorption cross section of space-time scalars on a static D2-brane, in global coordinates, wrapped on the S 2 of an AdS 2×S 2×CY 3 geometry. We discuss its relevance for the construction of the dual quantum mechanics of Calabi-Yau black holes.

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.