Partial Cross Sections Research Articles

New 209Bi photodisintegration data and physical criteria of data reliability

The well-known problem of noticeable disagreements between photoneutron cross sections from various experiments was discussed in detail for 209Bi. Data for partial photoneutron reactions cross sections obtained at Livermore (USA) using quasimonoenergetic annihilation photons and the method of neutron multiplicity sorting were analyzed using the objective physical criteria and the experimental-theoretical method for evaluation. Because of significant systematic uncertainties involved in the method for determining the neutron multiplicity, experimental data do not satisfy the criteria of reliability and differ noticeably from the evaluated data. The new experimental data for 209Bi (γ, in) reactions with i = 1–4 were obtained using quasimonochromatic laser Compton-scattering (LCS) γ-ray beams at the NewSUBARU synchrotron radiation facility and the novel technique of direct neutron-multiplicity sorting with a flat-efficiency detector. It was found that new σ(γ, 1n), σ (γ, 2n), and σ (γ, 3n) contradict noticeably to the Livermore data. It was shown that at the same time the new 209Bi photoneutron cross-sections are in good agreement with data evaluated using experimental-theoretical method and assuring the reliability of those.

Convergent close-coupling approach to proton collisions with helium

SynopsisWe develop a two-center wave-packet convergent close-coupling approach to proton collisions with helium including electron exchange. The convergence of the final results is studied in terms of the included projectile- and target-centered pseudostates. We present electron-capture and single- and double-ionisation cross sections in the projectile energy range from 15 keV to 1 MeV. We also provide partial cross sections for electron capture and direct excitation into the n = 2 shell states of hydrogen and helium, where n is the principal quantum number of the final state. Our results are in good agreement with available experimental data and other calculations.

Monte Carlo simulation of γ and fission transfer reactions using extended ℛ-matrix theory

This paper comes back on the accuracy of the surrogate-reaction method (SRM) historically used for neutron-induced average partial cross sections inference from measured surrogate-reaction probabilities. The SRM level of performance is examined in relation to a reasonably accurate reference calculation performed with the 𝒜𝒱𝒳𝒮ℱ-ℒ𝒩𝒢 code [1] through a challenging test case : the 240Pu* compound system. This paper argues on some ingredients of the reference calculation [2] and returns some hints about the failure now well-known of the neutron-induced γ average cross section inference. It shows also that in some special cases, the SRM can be poorly accurate also in terms of neutron-induced fission average cross section inference.

Compression bearing capacity of rolled H-beam end with partial cross-section loss

Compression bearing capacity of rolled H-beam end with partial cross-section loss

Hygrothermal performance of timber-concrete composite panels – theoretical investigation

The concrete layer as a part of the timber-concrete composite (TCC) element makes it possible to maintain the accumulated heat and thus reduce the energy required for heating. Especially for buildings used for a sauna, swimming pools or wellness. In the TCC cross-section due to uneven thermal and humidity deformation of both materials, additional stresses occur. It can lead to the failure of partial cross-sections or composite connection. The aim of the research is to investigate the influence of changing humidity and temperature conditions of the environment on the composite adhesively bonded TCC panels without the influence of other phenomena such as mechanical stress or the effect of concrete shrinkage. The paper presents the results of the preliminary theoretical investigation before the realization of measurements on prepared specimens.

Theoretical partial ionization cross sections by electron impact for production of cations from CH3OH, CO2 and NH3

In the present article, the Plane Wave Born Approximation (PWBA) along with Generalised Oscillator Strength (GOS) proposed by Weizsacker-Williams has been employed to calculate the partial ionization cross sections due to electron impact for production of cations (CH3OH+, CH2OH+, CH2O+, CH3+, CH2+ CHO+, CH+, C+, CO+, OH+, H2+ and H+) from methanol, for production of cations (CO2+, CO+, O+ and C+) from carbon dioxide and for production of cations (NH3+, NH2+, NH+, N+ and H+) from ammonia from the ionization threshold to 1 keV. The use of GOS given by Weizsacker-Williams breaks the expression of cross section into two terms, Bethe cross section and Mott cross section. Both terms depend on Optical Oscillator Strength (OOS). Furthermore, binary encounter theory has also been used. By summing all the partial ionization cross sections, total ionization cross sections are also obtained. The calculated cross sections are compared with the previously available experimental data and theoretical cross sections. The present calculations are found in remarkable agreement with available experimental data and other previous theoretical results.

Electron impact ionization cross sections of hydrogen fluoride molecule.

Partial and total ionization cross sections of hydrogen fluoride molecule are determined from the ionization threshold to high energy (5 KeV) by using a modified Jain-Khare semiempirical approach. Partial single and double differential cross sections with their sums (total) through direct and dissociative ionization have been also evaluated at fixed primary electron energies 100 eV, 200 eV, and 500 eV. There is no other data for partial ionization cross sections and differential ionization cross sections for comparison. In this paper, the total ionization cross sections data have compared with available experimental data and/or with other theoretical data which are available from intermediate to high energy. It is found that the present result gives a better account for the ionization cross sections up to higher energies.

Reliability of Neutron Yield Cross Sections on 12C–127I Isotopes in Proton-Induced Reactions Evaluated Using GEANT4 Package for Proton Therapy Applications

The work is aimed at studying the reliability of proton-induced neutron yield cross sections on 12C–127I biological tissue isotopes using the GEANT4 Monte Carlo simulation package, which is commonly applied for dosimetry calculations in proton therapy. Because of the lack of experimental results on the neutron yield for most of the isotopes considered, the simulated cross sections are first compared with theoretical data acquired using the TALYS nuclear reaction package, and the partial reaction cross sections calculated in TALYS are in turn analyzed in comparison with available experimental results. The mismatch between theory and experiment allows one to suggest a significant uncertainty in the calculation of the neutron doses associated with the isotopes under consideration.

Electron capture in collisions of Li3+ ions with ground and excited states of Li atoms**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFA0402300), the National Natural Science Foundation of China (Grant No. 11774037), International Atomic Energy Agency, China (Grant No. 23196/R0), and the Science Challenge Project of China (Grant No. TZ2016001).

The electron capture processes in collisions of Li3+ ion with Li(1s22s) and Li(1s22p0,1) are investigated by using the two-center atomic orbital close-coupling method in the energy range from 0.1 keV/u to 300 keV/u. The interaction of the active electrons with the target ion is represented by a model potential. The present results for the Li3+–Li(1s22s) system are compared with the available theoretical data and general agreement is obtained for the high collision energies. It is also found that the total and partial electron capture cross sections are sensitive to the initial charge cloud alignment in the low energy region.

Energy Correlations of α-Particles in the 8Be-Nucleus Ground-State Formation Channel of the 12C(γ,3α) and 16O(γ,4α) Reactions

The method of diffusion chamber in the magnetic field making use of a bremsstrahlung beam with a maximum photon energy of 150 MeV is applied to study the 12C(y,3a) and 16O(y,4a) reactions. A resonance identified as the ground state of 8Be nucleus is found in the distribution of events over the energy of the relative motion of two a-particles. The partial cross-sections of the 8Be nucleus formation channels are measured. It is shown that the mechanism of interaction between a y-quantum and a virtual a-particle pair takes place in this case.

Intruder dominance in the 02+ state of Mg32 studied with a novel technique for in-flight decays

The development of advanced γ-ray tracking arrays allows for a sensitive new technique to investigate elusive states of exotic nuclei with fast rare-isotope beams. By taking advantage of the excellent energy and position resolution of the Gamma-Ray Energy Tracking In-beam Nuclear Array, we developed a novel technique to identify in-flight isomeric decays of the 0⁺₂ state in 32Mg populated in a two-proton removal reaction. We confirm the 0⁺₂→2+1γ-ray transition of ³²Mg and constrain the 0⁺₂ decay lifetime, suggesting a large collectivity. The small partial cross section populating the 0⁺₂ state in this reaction provides experimental evidence for the reduced occupancy of the normal configuration of the 0⁺₂ state, indicating the intruder dominance of this state.

Resonant states 0+ of the Boron isotope 8B from the Jost-matrix analysis of the partial cross-sections

The available [Formula: see text]-matrix parametrization of experimental data on the excitation functions for the elastic and inelastic [Formula: see text] scattering at the collision energies up to 3.4[Formula: see text]MeV is used to generate the corresponding partial-wave cross-sections in the states with [Formula: see text]. Thus, obtained data are fitted using the semi-analytic two-channel Jost matrix with a proper analytic structure and some adjustable parameters. Then the spectral points are sought as zeros of the Jost matrix determinant (which correspond to the [Formula: see text]-matrix poles) at complex energies. The correct analytic structure makes it possible to calculate the fitted Jost matrix on any sheet of the Riemann surface whose topology involves not only the square-root but also the logarithmic branching caused by the Coulomb interaction. In this way, two overlapping [Formula: see text] resonances at the excitation energies [Formula: see text] and [Formula: see text][Formula: see text]MeV have been found.

59 POLYGENIC RISK SCORES ANALYSES IN ANTIPSYCHOTIC-INDUCED WEIGHT GAIN

The nuclear astrophysics setup at the Institute for Nuclear Physics, University of Cologne, Germany is dedicated to measurements of total and partial cross sections of charged-particle induced reactions at astrophysically relevant energies. These observables are key ingredients for reaction network calculations of various stellar scenarios, and crucial for the understanding of the nucleosynthesis of elements. The experiments utilize the high-efficiency γ-ray spectrometer HORUS, and the 10 MV FN-Tandem accelerator. An updated target chamber as well as further experimental methods established in the last years will be presented which allow to measure cross sections down to the nb region. The reliability of the measured cross sections is proven by a 89Y(p, γ)90Zr commissioning experiment. Additionally, an application for nuclear astrophysics will be presented. The results of a 93Nb(p, γ)94Mo experiment will be discussed as well as their deviations compared to formerly reported results.

Mutual Neutralization in Li+−D− Collisions: A Combined Experimental and Theoretical Study

Abstract We present a combined experimental and theoretical study of the mutual neutralization (MN) process in collisions of lithium ions (Li+) with deuterium anions (D−) at collision energies below 1 eV. We employ a merged-beam apparatus to determine total and state-to-state MN cross sections. We perform nuclear dynamics calculations using the multichannel Landau–Zener model based on accurate ab initio molecular data. We obtain an excellent agreement between the experimental and theoretical results over the energy range covered in this work. We show that the basis sets used in the ab initio calculations have a limited influence on the total cross section, but strongly impacts the results obtained for the partial cross sections or the reaction branching ratios. This demonstrates the important role of high-precision measurements to validate the theoretical approaches used to study gas-phase reactive processes. Finally, we compute MN rate coefficients for Li+ + H− and Li+ + D−, and discuss their significance for astrochemistry models.

Resonance cross-section formula for low-energy elastic scattering

A simple analytical formula for partial wave cross section describing low-energy elastic scattering in the presence of a shape resonance located near the elastic threshold is proposed. The formula is based on the extension of the regularized method of analytical continuation in the coupling constant (RAC) recently proposed by Hor\'a\ifmmode \check{c}\else \v{c}\fi{}ek and co-workers. The RAC method provides the complex energies of resonances and virtual states requiring as input information a set of real bound state energies of a perturbed system for which standard highly sophisticated numerical codes may be employed. No scattering calculations are needed. These parameters define the low-energy partial wave resonance scattering cross section. Cross sections are calculated for the $2{s}^{2}\ensuremath{\varepsilon}p\phantom{\rule{0.16em}{0ex}}^{2}P^{0}$ state of beryllium and $3{s}^{2}\ensuremath{\varepsilon}p\phantom{\rule{0.16em}{0ex}}^{2}P^{0}$ of magnesium. The results compare well with recently published data.

Residues of the S-matrix for several [formula omitted] resonances from the Jost function analysis

Parameters of the O16 resonances 0+, 1−, 2+, 3−, and 4+ as well as the corresponding residues of the S-matrix are extracted from experimental data on elastic α12C scattering. This is done by locating zeros of the Jost function at complex energies. The Jost function is constructed by fitting the corresponding partial cross sections for the elastic α12C-scattering. These cross sections are obtained from the available R-matrix analysis of the raw experimental data. An exact semi-analytic representation for the Jost function is used, where all the factors responsible for the branching of the Riemann surface are given explicitly. The remaining unknown functions in this representation are approximated by several terms of the Taylor series where the expansion coefficients serve as the data-fitting parameters. Such an approximation does not affect the correct analytic structure of the Jost function, and thus the corresponding analytic structure of the S-matrix also remains correct.

Phase diagrams of liquid-phase mixing in multi-component metal-organic framework glasses constructed by quantitative elemental nano-tomography

Several distinct mixing processes and resulting microstructures have recently been reported in multicomponent glasses prepared from multiple metal-organic frameworks. Here, two illustrative examples of multicomponent zeolitic imidazolate framework (ZIF) glasses, the (aTZIF-4-Co)0.5(agZIF-62)0.5 blend and the ag[(ZIF-67)0.2(ZIF-62)0.8] flux melted glass, are studied. These materials are characterized by quantitative X-ray energy dispersive spectroscopy in the scanning transmission electron microscope. By advancing a partial ionization cross section methodology using standards of arbitrary morphology, quantitative nanoscale elemental analysis throughout the glass volume is achieved. In turn, phase diagrams describing the mixing states are presented, offering mechanistic insight into the formation of the observed microstructures. Significant miscibility was observed in ag[(ZIF-67)0.2(ZIF-62)0.8]. These findings establish phase-segregation and interdiffusion as two processes in multicomponent glass formation, which explains the different outcomes observed in blending and flux melting.

Reliability of Photonuclear Data: Various Experiments and Evaluations

The well-known problem of reliability of partial photoneutron cross-section data obtained using beams of quasimonoenergetic annihilation photons was discussed. Noticeable disagreements between data from various experiments were analyzed using physical data reliability criteria. The experimentally-theoretical method for evaluating of reaction cross sections satisfied physical criteria was used and new reliable data were obtained for many nuclei. The disagreements between newly evaluated cross sections and data from the IAEA Digital Photonuclear Data Library were discussed.

Ratio method for estimating uncertainty in calculated gamma cascades

The assessment of uncertainty on deduced quantities obtained through both measurement and modeling must include contributions from both components. There are several methods to estimate the uncertainty due to modeling, such as the parametric uncertainty and that stemming from model bias. However, in the case where experimental data exists for partial cross sections, such as discrete gammas emitted in the de-excitation of the product nucleus following the reaction, the discrepancy between the measured and modeled gamma cascades provides more information and allows for uncertainty estimation that can account for all types of model and data uncertainty. This work presents a method for estimating that uncertainty, using ratios of gammas to get a measure of the accuracy of different parts of the modeled gamma cascade. The gamma with the lowest intensity uncertainty is shown to be the best for determining the channel cross section with realistic uncertainties, indicating that it should be used rather than the most intense gamma or a sum of gammas. This method provides both a simple procedure for calculating realistic uncertainties and identifies the best gamma for use in converting a set of measured partial gamma cross sections to the deduced total channel cross section.

Jost-matrix analysis of the resonance 5He∗(3 2+) near the dt-threshold

Partial cross-sections of the [Formula: see text] and [Formula: see text] collisions in the quantum state [Formula: see text] near the [Formula: see text]-threshold, taken from an available [Formula: see text]-matrix analysis, are fitted using the semi-analytic multi-channel Jost matrix with proper analytic structure and some adjustable parameters. Then the spectral points are sought as zeros of the Jost matrix determinant (which correspond to the [Formula: see text]-matrix poles) at complex energies. The correct analytic structure makes it possible to calculate (analytically continue) the fitted Jost matrix on any sheet of the Riemann surface whose topology involves not only the square-root but also the logarithmic branching caused by the Coulomb interaction. As a result of such an analytic continuation, it was found that the previously established [Formula: see text]-resonance (at [Formula: see text]) and its shadow pole (at [Formula: see text]) both are split in overlapping pairs. Apart from studying the properties of a specific nuclear state, it is also proved for a general multi-channel problem that the Coulomb forces change the topology of the Riemann surface as well as destroy the so-called mirror symmetry of the [Formula: see text]-matrix.