Atomic Number Dependence Research Articles

Determination of effective atomic number, electron density and Kerma of some ferroelectric materials using mass attenuation coefficients in the energy range 1 keV -100 GeV

The effective atomic number Zeff and the corresponding effective electron density Nel of ferroelectric materials (BaCoF4, LiNbO3, KNbO3, BaTiO3, PbZrO3, PbTiO3, KNbO3, Bi4Ti3O12, KHPO4, PbBi2Nb2O9, SrBi2Ta2O9, Ba0.73Sr0.27TiO3 and Mg3B7O13Cl) has been calculated in the extended energy region from 1 keV – 100 GeV using WinXCom program. The total photon interaction with coherent and incoherent one can distinguish three energy regions are approximately E<1 keV, 10 keV<E<1 GeV and E>10 GeV. The main photon interaction processes in these regions are photoelectric absorption, incoherent (Compton) scattering and pair production. Zeff and Nel values also have been obtained for different processes such as coherent and incoherent scattering pair production in nuclear and electric field, photoelectric absorption and the variations are shown graphically. The variations are due to the presence of different elements in a compound. The behaviour of the energy dependence of electron density is similar to the energy dependence of effective atomic number. The photoelectric absorption is dominant for total coherent process for Kinetic energy released per unit mass (Kerma). Direct method is one of the method helpful to calculate effective atomic number for all types of materials, for all energies greater than 1 keV.

External Bremsstrahlung Studies on Films of Lead Monoxide Filled Polycarbonate Composite

The development of high-Z (high atomic number) radiation shielding materials is vital in order to protect personnel who work with harmful gamma radiation sources. At the same time, the emission of external bremsstrahlung (EB) radiation in those shielding materials when the radiation source emits beta particles as well as gamma radiation is also of prime concern.The production of EB in films of lead monoxide (PbO) loaded polycarbonate (PC) composite at eleven different filler levels (FLs) varying, in terms of weight fraction, from 0.0 % up to 10.0 % were investigated experimentally by using beta particles from strontium-90/yttrium-90 (90Sr/90Y) radioactive source. A nonlinear relation is observed between EB intensity and target thickness. The effective atomic numbers of the prepared PbO-filled PC composite films (at different FLs) were determined via EB measurements, followed by calculations, and the values obtained were compared with the modified atomic numbers which were determined for the same composite films (at different FLs) using the Markowicz and Van Grieken equation, and it was found that they are in good agreement. Finally, the atomic number dependence of EB in these composite films (PbO-filled PC composites) has been studied. It is obtained that the intensity of EB spectra depends on the square of the atomic number of the target material.

Detailed Analysis of Spectra from Ga-like Ions of Heavy Elements Observed in High-Temperature Plasmas

This study has systematically investigated the atomic number (Z) dependence of spectra from gallium-like (Ga-like) ions of heavy elements. We have mainly analyzed the experimental spectra recorded in high-temperature plasmas produced in the Large Helical Device (LHD) for various elements with atomic numbers from 57 onward. The measured wavelengths are compared with theoretical values calculated with a multi-configuration Dirac Fock code. As a result, we have successfully obtained Z-dependent wavelengths of several prominent transitions of Ga-like ions, including a magnetic dipole (M1) transition. Many of them have been experimentally identified for the first time in this study. The present results manifest the significant effects of configuration interaction and spin–orbit interaction for highly charged heavy ions.

Local structure analysis of disordered materials via contrast variation in scanning transmission electron microscopy

The crystallographic structures of disordered materials are typically analyzed using diffractometry techniques, such as x-ray diffraction (XRD), neutron diffraction (ND), and electron diffraction (ED). Here, we demonstrate a novel technique to analyze the local structure of disordered materials via scanning transmission electron microscopy (STEM) under a contrast variation scheme. Contrast variation is a scheme used for the analysis of bulk materials, which combines two different diffractometry techniques with discrete scattering factors, such as ND and XRD. The STEM image contrasts of annular dark-field (ADF) and annular bright-field (ABF) imaging, which are characterized by different atomic number dependences, are simultaneously utilized. Simulated STEM images of amorphous SiO2 are examined using Fourier transform and autocorrelation operations, revealing that the Fourier transforms of ADF and ABF images are consistent with the results of conventional XRD/ED and ND techniques, respectively. The autocorrelation of the ABF image indicates the short-range ordering of light elements, which cannot be accomplished using conventional TEM, ED, and XRD techniques. As such, employing the contrast variation scheme in STEM imaging paves the way for analyzing the local crystallographic structure of non-monoatomic materials.

Superalkali-alkalide ion pairs δ+(M-HMHC)-M’ δ - (M, M’ = Li, Na and K) serving as high-performance NLO molecular materials

For the stable superalkali-alkalide ion pairs in alkalide solutions, a DFT study was performed to investigate the nonlinear optics (NLO) responses of δ +(M−HMHC)-M’ δ - (M, M’ = Li, Na and K). The NLO responses display obvious alkali metal atomic number dependence (M’). From δ +(M−HMHC)-Li δ - to δ +(M−HMHC)-K δ -, the increases of the static and dynamic first hyperpolarizabilities constitute a 1 ∼ 3 orders of magnitude improvement.

Band and optical properties of arsenene and antimonene lateral heterostructure by first-principles calculations

Construction of heterostructures can circumvent the shortcomings of 2D material components and has potential for applications in optoelectronic devices . Therefore, further development and construction of novel 2D materials is highly important. In this paper, a seamless lateral heterostructure (LHS) based on arsenene (As) and antimonene (Sb) along armchair (AC) and zigzag (ZZ) interfaces is predicted, and the band structures and optical absorption properties with the different interfaces are calculated from first principles . An indirect to direct band structure transition can be observed when the LHS interface changes from AC to ZZ. Additionally, the band gaps of the different (AC and ZZ) heterostructure types exhibit strong atomic number dependences, and can be narrowed from 1.1 to 0.45 eV and from 0.57 to 0.50 eV, respectively. The partial density of states (PDOS) and the conduction band minimum-valence band maximum (CBM-VBM) characteristics clarify the contributions from the different orbits to the band structures around the Fermi level. It should be noted that As/Sb lateral heterostructures have unique optical absorption characteristics in the mid-infrared range. Our predictions highlight the potential applications of As and Sb LHSs in electronics and optoelectronics. These results provide another 2D material with potential applications in mid-infrared optoelectronic devices. • Predict a lateral heterostructure made from As and Sb with armchair and zigzag interfaces. • Indirect to direct band structure change occurs with armchair to zigzag variation. • The lateral heterostructure band gaps narrowed to 0.50 eV for zigzag. • Unique optical absorption characteristics are found in the mid-infrared range.

First measurement of coherent ρ0 photoproduction in ultra-peripheral Xe–Xe collisions at [formula omitted] TeV

The first measurement of the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Xe–Xe collisions at sNN=5.44 TeV is presented. This result, together with previous HERA γp data and γ–Pb measurements from ALICE, describes the atomic number (A) dependence of this process, which is particularly sensitive to nuclear shadowing effects and to the approach to the black-disc limit of QCD at a semi-hard scale. The cross section of the Xe+Xe→ρ0+Xe+Xe process, measured at midrapidity through the decay channel ρ0→π+π−, is found to be dσ/dy=131.5±5.6(stat.)−16.9+17.5(syst.) mb. The ratio of the continuum to resonant contributions for the production of pion pairs is also measured. In addition, the fraction of events accompanied by electromagnetic dissociation of either one or both colliding nuclei is reported. The dependence on A of cross section for the coherent ρ0 photoproduction at a centre-of-mass energy per nucleon of the γA system of WγA,n=65 GeV is found to be consistent with a power-law behaviour σ(γA→ρ0A)∝Aα with a slope α=0.96±0.02(syst.). This slope signals important shadowing effects, but it is still far from the behaviour expected in the black-disc limit.

Effect of Nd3+ ions on radiation attenuation properties of PbF2–TeO2–WO3 glass system for shielding applications

This study aims to investigate the utility of using 15PbF2–(60x)TeO2–25WO3–xNd2O3 (0.1≥x≥1.5) glasses in the nuclear shielding applications for mixed radiation fields at energies ranging from 15keV to 15MeV. The effect of Nd3+ ions on gamma attenuation properties of the present glass system was discussed in detail. The radiation attenuation features were investigated for the present glass system by using Monte Carlo radiation transport simulation via Geant4 toolkit. The simulation results were theoretically approved by using Phy-X approach over the entire considered energy range. The obtained results indicate that the values of Zeff and Neff were both highest in the in the τ/ρ dominated energies due to the atomic number dependence of the cross sections of the τ/ρ absorption processes. Moreover, FNRCS values were 0.1152, 0.1152, 0.1153, and 0.1153cm−1 for PWTN1, PWTN2, PWTN3, and PWTN4 respectively. Finally, an extensive comparative study is also presented between the studied glass system and standard traditional shielding materials. The study suggests PWTN4 is the best photon shield amongst the studied PWTN-glasses.

X-Ray Spectroscopy in the Microcalorimeter Era. II. A New Diagnostic on Column Density from the Case A to B Transition in H- and He-like Iron

Abstract The Soft X-ray Spectrometer on board Hitomi, with the unprecedented resolving power of R ∼ 1250, allowed the detection of members of the Fe xxv Kα complex emission spectra from the center of the Perseus Cluster. In this paper, we introduce a novel method of measuring the column density using the optically thin (Case A) to optically thick (Case B) transition for one- and two-electron systems. We compare the Fe xxv K α line ratios computed with CLOUDY with that from the Hitomi observations in the outer region of the Perseus core using collision strengths from different atomic data sets, and obtain good agreement. We also show the effect of turbulence on Fe xxv Kα line ratios and interplay between column density and metallicity. Additionally, we discuss the atomic number dependence of transition probabilities for allowed and unallowed transitions, which causes highly charged He-like systems, such as Fe xxv, to behave fundamentally differently from He i.

Momentum distribution of the electron pair from the charged lepton flavor violating process μ−e−→e−e− in muonic atoms with a polarized muon

The $\mu^-e^-\to e^-e^-$ process in a muonic atom is one of the promising probes to study the charged lepton flavor violation (CLFV). We have investigated the angular distribution of electrons from the polarized muon of the atomic bound state. The parity violating asymmetric distribution of electrons is analyzed by using lepton wave functions under the Coulomb interaction of a finite nuclear charge distribution. It is found that the asymmetry parameters of electrons are very sensitive to the chiral structure of the CLFV interaction and the contact/photonic interaction. Therefore, together with the atomic number dependence of the decay rate studied in our previous work, the angular distribution of electrons from a polarized muon should be a very useful tool to constrain the model beyond the standard model.

Differential electron scattering cross-sections at low electron energies: The influence of screening parameter

For quantitative electron microscopy the comparison of measured and simulated data is essential. Monte Carlo (MC) simulations are well established to calculate the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) intensities on a non-atomic scale. In this work we focus on the importance of the screening parameter in differential screened Rutherford cross-sections for MC simulations and on the contribution of the screening parameter to the atomic-number dependence of the HAADF-STEM intensity at electron energies ≤ 30 keV. Materials investigated were chosen to cover a wide range of atomic numbers Z to study the Z dependence of the screening parameter. Comparison of measured and simulated HAADF-STEM intensities with different screening parameters known from the literature were tested and failed to generally describe the experimental data. Hence, the screening parameter was adapted to obtain the best match between experimental and MC-simulated HAADF-STEM intensities. The Z dependence of the HAADF-STEM intensity was derived.

Atomic number dependence of Z contrast in scanning transmission electron microscopy

Annular dark-field (ADF) imaging by scanning transmission electron microscopy (STEM) is a common technique for material characterization with high spatial resolution. It has been reported that ADF signal is proportional to the nth power of the atomic number Z, i.e., the Z contrast in textbooks and papers. Here we first demonstrate the deviation from the power-law model by quantitative experiments of a few 2D materials (graphene, MoS2 and WS2 monolayers). Then we elucidate ADF signal of single atoms using simulations to clarify the cause of the deviation. Two major causes of the deviation from the power-law model will be pointed out. The present study provides a practical guideline for the usage of the conventional power-law model for ADF imaging.

Effective Atomic Number Dependence of Radiological Parameters of Some Organic Compounds at 122 KeV Gamma Rays

Mass attenuation coefficient is a fundamental parameter of radiation interaction, from which the other radiological parameters like half Value Layer [HVL], tenth Value Layer [TVL], total atomic and electronic cross-sections, mass energy absorption coefficient, KERMA, CT number and effective atomic number are deduced. These parameters are extensively required in a number of fields such as diagnostic radiology, gamma ray spectroscopy, fluorescence analysis and reactor shielding. In the present work, mass attenuation coefficients are determined experimentally for some organic compounds at 122 keV incident photons using narrow-beam transmission geometry to establish a relation between effective atomic number (Zeff) and other deduced parameters. The experimental data for all these parameters are compared with the values deduced from WinXcom software package and are found to agree within experimental estimated errors. This study gives some insight about the photon interaction in some organic compounds whose effective atomic numbers match with some human body fluids.

Improved analysis for μ−e−→e−e− in muonic atoms by photonic interaction

Studies of the charged lepton flavor violating process of $\mu^-e^-\to e^-e^-$ in muonic atoms by the four Fermi interaction [Y. Uesaka \textit{et al}., Phys. Rev. D {\bf 93}, 076006 (2016)] are extended to include the photonic interaction. The wave functions of a muon and electrons are obtained by solving the Dirac equation with the Coulomb interaction of a finite nuclear charge distribution. We find suppression of the $\mu^-e^-\to e^-e^-$ rate over the initial estimation for the photonic interaction, in contrast to enhancement for the four Fermi interaction. It is due to the Coulomb interaction of scattering states and relativistic lepton wave functions. This finding suggests that the atomic number dependence of the $\mu^-e^-\to e^-e^-$ rate could be used to distinguish between the photonic and the four Fermi interactions.

Analytical dependence of effective atomic number on the elemental composition of matter and radiation energy in the range 10–1000 keV

Abstract In the present paper, a universal analytical dependence of effective atomic number on the composition of matter and radiation energy is proposed. This enables one to consider the case of a strong difference in the elemental composition with respect to their atomic numbers over a wide energy range. The contribution of photoelectric absorption and incoherent and coherent scattering during the interaction between radiation and matter is considered. For energy values over 40 keV, the contribution of coherent scattering does not exceed approximately 10% that can be neglected at a further consideration. The effective atomic numbers calculated on the basis of the proposed relationships are compared to the results of calculations based on other methods considered by different authors on the basis of experimental and tabulated data on mass and atomic attenuation coefficients. The examination is carried out for both single-element (e.g., 6C, 14Si, 28Cu, 56Ba, and 82Pb) and multi-element materials. Calculations are performed for W1−xCux alloys (x = 0.35; x = 0.4), PbO, ther moluminescent dosimetry compounds (56Ba, 48Cd, 41Sr, 20Ca, 12Mg, and 11Na), and SO4 in a wide energy range. A case with radiation energy between the K- and L1-absorption edges is considered for 82Pb, 74W, 56Ba, 48Cd, and 38Sr. This enables to substantially simplify the calculation of the atomic number and will be useful in technical and scientific fields related to the interaction between X-ray/gamma radiation and matter.

Extreme ultraviolet spectroscopy and atomic models of highly charged heavy ions in the Large Helical Device

We report recent results of extreme ultraviolet (EUV) spectroscopy of highly charged heavy ions in plasmas produced in the Large Helical Device (LHD). The LHD is an ideal source of experimental databases of EUV spectra because of high brightness and low opacity, combined with the availability of pellet injection systems and reliable diagnostic tools. The measured heavy elements include tungsten, tin, lanthanides and bismuth, which are motivated by ITER as well as a variety of plasma applications such as EUV lithography and biological microscopy. The observed spectral features drastically change between quasicontinuum and discrete depending on the plasma temperature, which leads to some new experimental identifications of spectral lines. We have developed collisional-radiative models for some of these ions based on the measurements. The atomic number dependence of the spectral feature is also discussed.

Neutron production by cosmic-ray muons in various materials

The results obtained by studying the background of neutrons produced by cosmic-ray muons in underground experimental facilities intended for rare-event searches and in surrounding rock are presented. The types of this rock may include granite, sedimentary rock, gypsum, and rock salt. Neutron production and transfer were simulated using the Geant4 and SHIELD transport codes. These codes were tuned via a comparison of the results of calculations with experimental data: in particular, with data of the Artemovsk research station of the Institute for Nuclear Research (INR, Moscow, Russia), as well as via an intercomparison of results of calculations with the Geant4 and SHIELD codes. It turns out that the atomic-number dependence of the production and yield of neutrons has an irregular character and does not allow a description in terms of a universal function of the atomic number. The parameters of this dependence are different for two groups of nuclei-nuclei consisting of alpha particles and all of the remaining nuclei. Moreover, there are manifest exceptions from a power-law dependence, for example, argon. This may entail important consequences both for the existing underground experimental facilities and for those under construction. Investigation of cosmic-ray-induced neutron production in various materials is of paramount importance for the interpretation of experiments conducted at large depths under the Earth's surface.

Remarkable NLO responses of hyperalkalized species: the size effect and atomic number dependence

The large first order static hyperpolarizabilities (βo) of hyperalkalized species establish their strong NLO responses.

Electron affinity and ionization potential of two-dimensional honeycomb sheets: A first principle study

We perform first principle calculations based on density functional theory to study the electron affinity and ionization potential of two-dimensional structures of carbon family, group-III-nitride family and transition-metal dichalcogenide family. We found and explained the atomic number dependence of electron affinity and ionization potential.

Electron backscattering from solid targets: Elastic scattering calculations

Analytical expression of the target atomic number dependence of the numerical coefficient in the Nigam atomic screening factor is proposed here to approximate the Rutherford elastic scattering cross sections for slow electron beams impinging on selected solid targets (from Be to Au) in the primary energy range 1–4keV. Applications are then proposed in terms of Monte Carlo calculation of backscattering coefficient. In this respect, tabulations of backscattering coefficients are here reported for slow electrons in solid targets of interest pointing out a reasonable agreement with the data available in the literature. Analytical expressions of the target atomic number dependence of the electron backscattering coefficient is also suggested for selected electron primary energies ranging from 1 to 4keV allowing thus an accurate determination of backscattering coefficients for low-energy electrons in solid targets without any resort in Monte Carlo type calculations.