Atomic Cross Sections Research Articles

Sub-Doppler resonances caused by photoionization of atoms in thin gas cells

By analogy with the well-tested method of high-resolution spectroscopy in thin gas cells for the processes of optical pumping of atoms, this work shows the possibility of detecting narrow sub-Doppler optical resonances caused directly by straight photoionization of atoms (or molecules) in such cells. The structure of the established nontrivial resonances substantially depends on the probability of photoionization of atoms and dimensions of such a cell, the internal thickness of which is many times smaller than its diameter. Of particular interest is the broadening of the considered sub-Doppler resonances, which is determined directly by the photoionization cross section of atoms and the intensity of radiation causing ionization. Under certain conditions, such photoionization broadening can be measured experimentally with high accuracy, as a result of which it is possible to obtain new important information about ionization processes in atoms and molecules. Keywords: sub-Doppler resonances, photoionization of atoms, thin gas cell, transit-time relaxation of atoms.

Study of Alpha Particle Impact Double Ionization Cross Sections of Cu Atom

Semi-classical binary encounter approximation has been used for the study of ionization cross sections of Cu atom at ground state. Projectile, alpha particle, with energy varying from threshold to 360 keV/amu are considered for direct double ionizations cross section. Out of the two path ways of ionization we have ruled out the indirect process (like excitation-auto ionization, Auger effect) of double ionization. We considered direct - ionization of outer shells of Cu atom. Vriens accurate expression of cross section for energy transfer ΔE(σΔE ) and Hertree-Fock velosity distribution function for the target electrons are used. The theoretical value of double ionization cross sections at impact energy 300 keV/amu is 0.98 x 10-16 cm2 which is same as experimental values at that impact energy. Above energy of 300 keV/amu, the calculated results underestimates the experimental data and at 360 keV/amu their magnitude are 0.77 x 10-16 and 1.0 x 10-16 respectively. Above impact energy of 75keV/amu, all the theoretical results have ratio factor within 2. Out of the total number of theoretical data 75% are under valid range of ratio factor 2 and among the valid range 41% have ratio factor below 1.325 and hence calculated results of double ionization cross section lie in the acceptable range. The linear correlation coefficient (R square) and standard deviation (SD) of linear fit are 0.6984 and 0.7883 respectively. In low energy range the theoretical results are more apart from corresponding experimental values and possess relatively more error compared to intermediate and higher energy region. Calculated results are in satisfactory agreement with experiment in intermediate and high energy range.

A study on radiation shielding potentials of green and red clayey soils in Turkey reinforced with marble dust and waste tire

The increasing radiation applications in our daily life makes it essential to protect ourselves from the harms of radiation by using alternative, cheap and natural materials. The present study aimed to analyze the radiation shielding abilities of green and red clayey soils from Oltu/Erzurum in Turkey, reinforced with waste tires and marble dust. For the purpose to investigate the shielding features of the samples, radiation attenuation parameters were determined by using EpiXS software, which can calculate partial or total cross-sections, partial or total mass attenuation coefficients, electron densities, effective atomic numbers, and buildup factors for energy absorption and exposure between 1keV and 1GeV. We compared the obtained mass attenuation coefficients and total atomic cross-section values of the samples with those of a widely used shielding material, ordinary concrete, to make a meaningful evaluation about the shielding potentials of the samples. To validate obtained values by EpiXS, we also calculated the mass attenuation coefficients of the samples by XCOM code, and compatible results were obtained. Among all the studied clayey soil samples, green clay reinforced with marble dust and waste tire has the highest shielding capability. It can also be mentioned that reinforcement with marble dust and waste tire improves the shielding ability of the clayey soils.

Gamma-Ray Attenuation Characteristics of Some Essential Amino Acids for 57Co, 192Ir, 18F, and 116mIn Sources

Purpose: In different tissues of the body, proteins are important parts that are made up of building blocks called amino acids. Considering the wide applications of radioactive sources in industry and medicine, the need to study the attenuation characteristics of amino acids is determined. Materials and Methods: To study the attenuation characteristics of five types of amino acids, MCNPX Monte Carlo code and XMuDat program were used. Linear and mass attenuation coefficients, half and tenth value layers, mean free path, effective atomic and electronic cross-sections, effective atomic numbers and effective electron densities were calculated. 57Co, 192Ir, 18F, and 116mIn gamma sources were considered for this study. To validate the theoretical results, the obtained values were compared with the available experimental data. Results: The difference between the theoretical and experimental results was less than 11%. The results showed that with increasing photon energy, the linear and mass attenuation coefficients and effective atomic and electronic cross-sections decreased, while the half and tenth value layers and mean free path quantities increased. Furthermore, the linear attenuation coefficients, the effective atomic and electronic cross-sections, as well as the effective atomic number values increased with increasing amino acid density, while the effective electron density behaves independently of the amino acid density. Conclusion: The presented theoretical methods produced data similar to experimental results with fair accuracy, so by using these methods, attenuation properties of other amino acids can be obtained over a wide range of energies.

Calculate Effective Atomic Number, Mass and Cross-Section Attenuation Coefficients for Nonanoic Acid by Using Gamma-Ray Sources

The effective atomic number (Z effective), total atomic cross-section (б Total) electron density (N effective) have been Measured depending on the mass attenuation coefficient (μ/ρ). By using Gamma-ray radiation (γ), emitted from sources (57𝐶𝑜, 133𝐵𝑎, 22𝑁𝑎, 137𝐶𝑠, 54𝑀𝑛, 𝑎𝑛𝑑 60𝐶𝑜) with energies from (0.122, 0.356, 0.511, 0.662, 0.84, 1.17, 1.275 𝑎𝑛𝑑 1.33𝑀𝑒𝑉) respectively. using the Sodium Iodide Scintillation Detectors NaI (Tl) at 662 keV and resolution about 8.2% have been measured the mass attenuation coefficients for the sample “Nonanoic acid its common name Pelargonic acid” it’s chemical formula C9H18O2. The data from the mass attenuation coefficient were then employed to study Zeffective, Neffective, and бtotal of the sample. In the presence of gamma-ray energy, it was discovered that the effective atomic number and effective electron densities first drop and they tend to remain nearly constant. The experimental values obtained by Zeffective and Neffective were in excellent agreement with the theoretical values. The theoretical data that is accessible is obtained from XCom, which is available online. The study's findings aid in understanding how (μ/ρ) values change when Zeff and Neff values vary in the case of H, C, and O based biological molecules such as fatty acids.

Some approaches to the calculation of the normalized Mott cross section, displacement cross section, and the Mott correction to the Bethe formula

A new exact representation for the normalized Mott cross section is obtained. Some earlier exact and approximate methods for its calculation are compared with the method proposed in this work. It is demonstrated that applying the suggested rigorous method, along with the approximate method of Lijian et al., is most preferable for the above calculations. Some modifications of Lijian’s method are proposed. Based on these modifications and the Lijian method itself, new analytical expressions are obtained for the Mott corrections to the Bethe stopping formula and the primary displacement cross section by fast electrons. It is shown that the highest fitting accuracy of the displacement cross sections is provided by the twice modified Lijian method. • A new exact representation for the normalized Mott cross section is proposed. • The modified and twice modified Lijian−Qing−Zhengming methods are suggested. • Based on these methods, a new analytical expression for Mott’s correction is obtained. • We also get in this way a new expression for the atomic displacement cross section.

Neutron/gamma radiation shielding characteristics and physical properties of (97.3−x)Pb−xCd–2.7Ag alloys for nuclear radiation applications

In this work, the shielding performance of (97.3–x)Pb–xCd–2.7Ag (x = 10, 18, and 30) ternary alloys against neutrons and gamma rays has been investigated. The microstructure, thermal and mechanical properties of the ternary alloys were examined. The total mass attenuation coefficients, for prepared alloys were determined at 662, 1173, and 1332 keV photon energies using NaI (Tl) scintillation detector. The theoretical values of were calculated using WinXCom program depending on the mixture rule. The estimated values were compared with the measured values for all investigated alloys. Atomic cross-section, σ a, electronic cross-section, σ e, effective atomic number, Z eff , effective electron number, N eff , and GP fitting parameters (b, c, a, Xk, and d) were determined. The exposure buildup factor, EBF, have been also calculated. Fast neutron attenuation for the prepared samples have been investigated via the macroscopic effective removal cross-section () calculation. Also, thermal neutron attenuation has been evaluated via neutron scattering calculator. The results show that the alloys containing 10 and 30% Cd compromise between superior tensile strength and Young modulus, while the pasty range, heat of fusion and ductility decreased with increasing Cd content. Moreover, the prepared ternary alloys have a high attenuation ability for gamma rays as the standard Pb. The increase of Cd ratio also significantly enhances the thermal neutron attenuation by amazing way along with the increase in the attenuation rate of fast neutrons.

A model potential for computing total ionization cross sections of atoms and molecules by electron impact

A model potential for computing total ionization cross sections of atoms and molecules by electron impact

Electromagnetic-Ray Absorption Using B2O3-PbO-Na2O Glass Mixtures as Radiation Protection Shields

In this work, Lead Borate glass system doped with sodium is prepared and fabricated using the melt-quenching technique. The glasses are prepared based on the empirical formula of xPbO, (80-x) B2O3, 20Na2O (where x=0, 10, 20, 30, 40, and 50). The densities of the samples are measured with the Archimedes method by using Benzene as an immersion liquid. The radiation shielding parameters of the prepared glass samples have been measured experimentally and calculated theoretically. The experimental mass attenuation coefficients are obtained by using a shielded NaI(Tl) detector at photon energies 511, 662, and 1173 keV of the radioactive sources 22Na, 137Cs, and 60Co respectively, where collimators of aperture diameter 3 mm are used to ensure that the detector absorbs a narrow beam of gamma rays. The calculated mass attenuation coefficients (µm), half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), effective electron density (Neff), atomic cross-section (σa), electron cross-section (σe) radiation protection efficiency (RPE) are performed theoretically by using WinXCom and Phy-X/PSD computer programs in the energy range from 1 keV to 1 GeV. The calculated parameters of the investigated glasses have been compared with the measured experimental values

Fullerite C60 optical constants in the C 1s NEXAFS region

Using data on the absorption cross sections the refraction coefficient spectral dependence n(E) and the spectra of the remaining optical coefficients (reflection coefficient, phase shift, and atomic form factor) in the fullerite C60 C 1s near edge X-ray absorption fine structure (NEXAFS) region (280–350 eV) were determined. For the n(E) calculations the Kramers-Kronig integral relations (KKRs) were used. The KKR computations were performed using data on atomic carbon absorption cross sections in the 10–30000 eV range and on solid and gaseous C60 – in the 0–120 eV. Absorption cross section spectrum in the fullerite C60 C 1s NEXAFS region were measured.

Photoionization, Rayleigh, and Raman scattering cross sections for the alkali atoms

An extensive set of photoionization, Rayleigh and Raman scattering cross sections have been presented for the alkali atoms: lithium, sodium, potassium, rubidium, and cesium. This set consists of 16 photoionization cross sections and 47 Rayleigh and Raman scattering cross sections for each atom. Results are presented for incident photon energies from 0.01 to 0.5 Hartrees. These cross sections have been calculated with a fully relativistic atomic structure model. Polarization effects have been accounted for through the use of a semi-empirical dipole polarization potential and modified dipole operator. The computational method utilizes a principal value integral over the target continuum to deal with pole terms that arise for incident photon energies above the ionization threshold. The cross sections are valid for incident photon energies both above and below the ionization threshold.

Determining the ratio of the number of recoil electrons to the number of photoelectrons using a new method

The problem in question is relevant due to discrepancy between the results of theoretical and known experimental studies of various interactions of ionizing emission photons with substances, in particular, photo effect and Compton scattering of these photons. The study aimed at carrying out specific measurements using a new method of simultaneously determining the ratio of the number of recoil electrons to the number of photoelectrons. Analysis of the results showed that there are significant discrepancies between theoretical calculations and experimental data. New values of simultaneously measured ratios of cross-sections for heavy atoms using a method invented by the author, and old measurements of these ratios for light atoms usingWilson cloud chamber, when compared with theoretical calculations, show that a significant (by one order and more) one-direction discrepancy is seen for X-ray and gamma emissions over a range of energies in question.It is shown that these discrepancies might be attributed to the fact that an atomic electron is in a free state for a while. Compton scattering occurs with a free electron; photo effect involves only bound electrons. Therefore, Compton scattering cross section is proportional to a period of time, during which electron was in a free state, whereas photo effect cross section is proportional to a time period, during which electron was in a bound state. The article materials might be helpful to perform both fundamental, and applied studies on interaction of light quanta with substance including modelling the phenomena under examination.

Remarks on bosonic super-WIMP search experiments

Bosonic super--weakly interacting massive particles (WIMPs), including pseudoscalar and vector particles, are dark-matter candidates. To date, many underground experiments searches for super-WIMPs have been performed in the mass range of a few $\mathrm{keV}/{c}^{2}$ to $1\text{ }\text{ }\mathrm{MeV}/{c}^{2}$. All these searches utilize the absorption process of a super-WIMP by a target atom in the detector, which is similar to the photoelectric effect. We consider another process---namely, a Compton-like process. As an example, we compare the cross section of a germanium atom for the absorption process with that of a Compton-like process. Our findings indicate that the cross section for the Compton-like process becomes dominant relative to that for the absorption process for mass above approximately $150\text{ }\text{ }\mathrm{keV}/{c}^{2}$ for both pseudoscalar and vector super-WIMPs. In particular, the cross section for the Compton-like process for a vector super-WIMP becomes increasingly greater than that for the absorption process by 1 to 2 orders of magnitude in the $400\text{ }\text{ }\mathrm{keV}/{c}^{2}$ to $1\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ mass range, respectively. By including the Compton-like process, which has not been used in any other super-WIMP search experiments, the experimental upper limits can be improved.

Ion bombardment technique induced alterations in the surface chemical composition and shielding parameters of polymeric material

At present, ion beam technology is one powerful technique to improve the physico-chemical properties of polymeric material. In this work, ultra high molecular weight polyethylene samples were bombarded with 1 MeV He-ion beam at fluences ranging from 1×1013 to 5×1014 ions/cm2. The changes in the chemical composition of the treated layer caused by the ion beam were investigated. The hydrogen escapes due to the ion beam irradiations were measured by the nuclear reaction analysis (NRA) technique using the 1H(15N, αγ)12C reaction. The oxygen uptake has been studied by the Rutherford backscattering spectrometry (RBS) and Fourier transform infrared spectrometer (FTIR) techniques. The partial and total mass attenuation coefficients of photons at energies 81, 356, 511 and 1332 keV were estimated using the XCOM program (version 3.1). The obtained results showed that the hydrogen release was increasing with an increase in ion fluence. Moreover, important oxygen uptake of bombarded samples was also observed. These effects led to significant improvements in the surface characteristics of the treated materials such as changes in the shielding parameters. The changes in the mass attenuation coefficients (μ/ρ) were calculated relying on the incoming photon energies and the atomic concentrations of the elements that are present in the target material. The total atomic cross-sections and effective atomic numbers were calculated by using the data of the total mass attenuation coefficients. A decrease in both the total atomic cross-section and effective atomic numbers was noticed with an increase in the ion beam fluence.

Evaluation of radiation interaction parameters of some shape memory alloys

Abstract In this study, effective atomic number (Zeff), atomic (σta) and electronic cross section (σte) values of some shape memory alloys (SMA) were calculated at energies 5.9, 6.1, 8, 11.2, 25, 59.543, 75, 112, 149 keV. It has been observed that the obtained values of the calculated parameters vary depending on the photon intensity, chemical constitution and density of the alloys. Calculations were made using the WinXCom program and the graph of the change according to the energy of the obtained results was drawn. The results of this study are thought to be beneficial in the application of various fields.

Bomb Model of Radiosensitization by Metallic Nanoparticles

Metallic nanoparticles (NPs) have been shown to be effective in enhancing radiotherapy through photoelectric effect due to the large photoelectric interaction cross-sections of high atomic number atoms. Experiments, however, demonstrated a strong radiosensitizing effect of Gold and Gadoliniums NPs in vivo that is beyond the calculated macroscopic dose enhancement, and even beyond the microdosimetric properties of the Auger electrons following a photoelectric interaction. We propose to describe NPs in cells as a bomb to kill the cell at a probability during a photoelectric event, depending on biological properties of the cell.The biological damage caused by NPs may be categorized into local and non-local. The non-local part corresponds approximately to the macroscopic dose enhancement. Based on the reported in vivo NP concentration, the calculated contribution of this part is negligibly small, especially for MV beams. The local part of the damage is caused by the electron cascade near the NP surface following a photoelectric interaction. We model this effect as a bomb, which gives an upper limit of cell killing for a known NP concentration inside a cell or cell nucleus. We performed a Monte Carlo simulation of irradiating a Gd-based NP with a 250 kVp beam and a 6 MV FFF beam, and calculated the photoelectric interaction probability of GdNP per gray of dose to surrounding medium (water) and the distribution of the number of Auger cascade electrons generated per ionization. The increase in α of the Linear-Quadratic survival model can be calculated using the following equation for the mean number of lethal lesions due to local damage: Nlocal = Nionization·p = NNp·p1Gy·D·p = Δα·D where Δα = NNp·p1Gy·p, Nionization is the total number of NP ionizations that occur in the target (e.g., the nucleus), p is the probability of killing which is set to a value ≤1 when the number of electrons generated per ionization is > 1, and 0 otherwise, NNP is the average number of NPs in the target, D is the dose to the surrounding water due to the X-rays without NPs, and p1Gy is the probability of ionizing an NP when D is 1 Gy.Based on reported in vivo GdNP concentrations of ∼5.5 ppm, for 250 kVp X-rays, the upper limit on the increase in α will be 0.0008 Gy-1 for a 100 μm3 effective DNA volume. If the entire cell of a typical volume of 1000 μm3 is taken to be the target, the upper limit on the increase in α will be 0.008 Gy-1 and 9e-6 Gy-1, respectively for a typical 250kVp beam and a 6MV FFF beam. Radiosensitization may be predicted based on the NP concentrations in cells and the cell properties.The NP radiosensitization effect, which cannot be accounted for by macroscopic dose enhancement alone and has been failed to be described by many other microdosimetry studies, could be potentially described using a bomb model of NP. One of the consequences of this model is that the β does not change due to the presence of NP, which fits most experimental observations.

Gamma radiation shielding traits of B2O3–Bi2O3–CdO–BaO–PbO glasses

This paper evaluates the γ-radiation shielding traits of some new types of borate glasses of composition (70–x)B2O3–10Bi2O3–10BaO–10CdO–xPbO (where 0 ≤ x ≤ 20 mol%) prepared using melt quenching method. As-quenched samples were characterized to determine the effects of various PbO contents on their γ-radiation shielding properties. XRD patterns of the samples verified their amorphous nature. The Phy-X and XCOM was used to compute the mass attenuation coefficients of the glasses and then compared with the experimental data. The γ-radiation shielding performance of the proposed glasses were evaluated in terms of diverse attenuation parameters like mean free path, half and tenth value layer, atomic cross-section, electronic cross-section, effective atomic number and effective electron density. The γ-radiation shielding performance of the glasses were significantly improved with the increase of PbO contents. This new borate glass system is established to be advantageous for the radiation shielding applications.

Comparative study on results of calculating the effective atomic number by means of various methods in the photon energy region of 250–700 keV

The article presents the results of calculations of the effective atomic number Zef for the total atomic cross-section of multi-element substances LiF, MgSO4, CaSO4·2H2O, CaCO3, 3CdSO4·8H2O, CaSO4, ZnSO4, SrSO4, CdSO4, C4H6BaO4, BaSO4, CdWO4, Gd2O2S, PbWO4, PbO, UO2, UO at photon energies 272.9, 310.5, 320.07, 469.1, 514, and 661.6 keV. The calculation methods differ in parameters and formulas for the approximation of the total atomic cross-section of the interaction of photons with atoms of the substance. An analytical formula is proposed to calculate Zef. For CaSO4·2H2O and the W (65%) Cu alloy, the calculations were carried out in the range of 10–700 keV. Comparison of our results to experimental data and calculations according to the AUTO-Zeff program is carried out.

Study Total Atomic Cross-Sections, Effective Atomic Numbers, and Electron Densities for Palmitic Acid by Using Sources of Gamma Ray

The effective atomic number (Z effective), total atomic cross-section (б Total) electron density (N effective) have been Measured depending on the mass attenuation coefficient (μ/ρ). By using Gamma-ray radiation (γ), emitted from sources (57𝐶𝑜, 133𝐵𝑎, 22𝑁𝑎, 137𝐶𝑠, 54𝑀𝑛, 𝑎𝑛𝑑 60𝐶𝑜) with energies from (0.122, 0.356,0.511,0.662,0.84,1.17,1.275 𝑎𝑛𝑑 1.33𝑀𝑒𝑉) respectively. using the Sodium Iodide Scintillation Detectors NaI(Tl) at 662 keV and resolution about 8.2% have been measured the mass attenuation coefficients for the sample “Palmitic acid” it’s chemical formula C16H32O2. The data from the mass attenuation coefficient were then employed to study Z effective, N effective, and б total of the sample. In the presence of gamma-ray energy, it was discovered that the effective atomic number and effective electron densities first drop and they tend to remain nearly constant. The experimental values obtained by Z effective and N effective were in excellent agreement with the theoretical values. The theoretical data that is accessible is obtained from XCom, which is available online. The study's findings aid in understanding how (μ/ρ) values change when Zeff and Neff values vary in the case of H, C, and O based biological molecules such as fatty acids.

Gamma photon-neutron attenuation parameters of marble concrete by MCNPX code

The present study aims to investigate the gamma photon-neutron attenuation parameters of the marble concrete such as the linear attenuation coefficient (), Mass Attenuation Coefficient (MAC), Half Value Layer (HVL), neutron removal cross-section (∑R), and Exposure Buildup Factor (EBF) by MCNPX Monte Carlo code to examine the possibility of utilizing selected samples against gamma photon-neutron. The six types of marble concrete were exposed to different energies ranging from 511 to 1332 keV. The shielding effectiveness of the selected marble concrete was compared to each other and the obtained results show that the increment of the penetration depth causes an increase in the value of EBF and the sharp peak is monitored at 200 keV. The ∑R (neutron removal cross-section) values were also reported for all types of marble concrete. The outcomes depict that ∑R is strongly relevant to the weight fractions of light elements of the selected shielding materials. Furthermore, the variations of (total atomic cross-section) were reviewed and discussed versus wide energy ranges. Findings in all sections confirmed that NM-15 has the best gamma photon shielding quality in comparison with the other types of marble concrete, while NM-0 and NM-15 show the highest neutron proficiency.