Total Inelastic Cross Sections Research Articles

Calculations of positron scattering from small molecules

Recently, convergent close-coupling calculations have been completed for positron scattering from the carbon and oxygen atomic targets. These, together with previously completed calculations for atomic hydrogen, are utilized to perform positron scattering calculations for molecular hydrogen (H2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {H}_2$$\\end{document}), molecular oxygen (O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {O}_2$$\\end{document}), diatomic carbon (C2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {C}_2$$\\end{document}), carbon monoxide (CO), carbon dioxide (CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {CO}_2$$\\end{document}), ozone (O3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {O}_3$$\\end{document}), water (H2O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {H}_2\\hbox {O}$$\\end{document}), and methane (CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {CH}_4$$\\end{document}) through a modified independent atom approach. For these molecules, positronium-formation, direct ionization, electron-loss, elastic, total electronic excitation, total inelastic, and total cross sections are obtained for energies between 0.1 and 5000 eV. There is, in general, good agreement between the current results and past experiments for most transitions, particularly at high energies where this approach is expected to be most accurate.Graphic

Study of Electron Collisions with Isoprene, 1,2-Butadiene, and Their Isomers.

Isoprene, 1,2-butadiene, and their isomers play an important role in aerosols in the atmosphere, interstellar media, and extraterrestrial life. Since electrons are everywhere, studying how electrons interact with these molecules is an important part of studying such environments. To date, however, little investigation has been conducted in this area. Bearing this in mind, we conducted a thorough investigation to report the various electron scattering cross sections of isoprene, 1,2-butadiene, and their isomers. The methods used for this purpose are reliable within the limits of adopted model potentials. The optical potential method was used to get the total elastic and inelastic cross sections, while the complex scattering potential ionization contribution method was used to get the total ionization cross section from the inelastic contribution. The results from these approximations are pretty close to the results from earlier experiments and theories. Furthermore, most of these isomers are being explored for the first time. Besides, their isomeric effect is also discussed. A correlation between the cross sections of molecules is demonstrated, which can be used to predict cross sections of those molecules where previous data are not available.

Convergent close-coupling calculations of positron scattering from atomic carbon

We report on the extension of the single-center convergent close-coupling method to positron scattering on multielectron atoms, along with the development of a technique for separating the direct ionization and positronium-formation channels in single-center calculations. We have performed calculations of positron scattering on carbon and present total elastic, momentum transfer, excitation, direct ionization, total ionization, total inelastic, positronium-formation, stopping power, and total cross sections from threshold to 5000 eV. We also present oscillator strengths, the scattering length, the hidden Ramsauer-Townsend minimum, the energy of the positron-carbon virtual state, and the mean excitation energy. Agreement with electron-scattering experiment and positron-scattering theory for several cross sections has been demonstrated for high energies. However, discrepancies exist between different theoretical methods at lower energies and for the ionization and positronium-formation processes.

Electron interactions with analogous of DNA/RNA nucleobases: 3-hydroxytetrahydroFuran and α-Tetrahydrofurfuryl alcohol

We report quantitative results for electron induced molecular processes for DNA/RNA nucleobase analogous bio-molecules, 3-hydroxytetrahydrofuran (C4H8O2, 3hTHF) and α-tetrahydrofurfuryl alcohol (C5H10O2, THFA), which are similar in structure and functional group to backbone of DNA and RNA. We have employed spherical complex optical potential (SCOP) formalism to compute total elastic (Qel) and inelastic (Qinel) cross sections and used Complex Scattering Potential-ionization contribution (CSP-ic) method to obtain total ionization (Qion) and summed total excitation (∑Qexc) cross sections. These results obtained for a wide energy range (10 eV - 5 keV) may serve as the input parameters in predicting damage in biomolecular systems induced by secondary electrons caused by primary ionization radiation. We have observed a correlation between maximum Qion and molecular polarizability volume (α), ionisation energy (IE) and number of valence electrons (Nv). This work includes an attempt to estimate ∑Qexc for these molecules in normal state.

From 232Th(n, n’γ) cross sections to level production and total neutron inelastic scattering cross sections

To probe the neutron inelastic scattering off 232Th, an experiment took place at the EC-JRC Geel conducted with the experimental setup GRAPhEME to detect emitted γ-rays. The prompt γ-ray spectroscopy method was used and 70 experimental 232Th(n, n’γ) cross sections were obtained from the experimental data. Combining these cross sections, nuclear-structure data available in databases and hypotheses to complete the latter, neutron inelastic level production cross sections in 232Th and the total inelastic cross section were calculated. For the first time, the total inelastic cross section of an actinide nucleus was derived on the total neutron energy range from experimental data only. Comparisons of (n, n’) cross section data with evaluated data reveal a good agreement between them all above 300 keV of neutron energy. TALYS calculations are compatible but lower than the evaluated data.

On the need for precise nuclear structure data for high quality (n, n’γ) cross-section measurements

The necessary improvement of evaluated nuclear data for nuclear applications development is possible through new and high-quality measurements, often combined with appropriate nuclear-reaction modelling. In particular, improving inelastic cross-section evaluations requires new and high-quality data. We measure (n, n’γ) cross-sections using prompt γ-ray spectroscopy and neutron energy determination by time-of-flight. To extract, from these partial data, the total inelastic cross-section, we rely on theoretical model as well as nuclear structure data such as γ ray emission probabilities. This structure information, tabulated in databases, comes with uncertainty. This directly affects the precision of our results, regardless of how good the measurement is. In this paper, we will present the issue of limited precision structure data and its impact on nuclear reaction data quality in the case of neutron inelastic scattering measurements. We will also discuss how to foresee and mitigate the issue.

Electron impact inelastic molecular processes for deuterated compounds

In this theoretical work, electron induced inelastic molecular processes for deuterated molecules HD, D2, D2O, SiDx (x = 1–3), NDx (x = 1–3) and CDx (x = 2–4) are studied and quantified from ionisation threshold to 5 keV. The total inelastic cross section (Qinel) are computed using Spherical Complex Optical Potential (SCOP) and total ionisation cross sections (Qion) and total electronic excitation cross sections (∑Qexc) have been evaluated through the Complex Spherical Potential – ionisation contribution (CSP-ic) method. Electron driven inelastic effects for deuterated hydrogen (HD) are investigated for the first time in this study. This is the first report of total Qion for HD, SiDx (x = 1–3), NDx (x = 1,2), CDx (x = 2,3) molecules and maiden study of Qinel and ∑Qexc for all these molecules. Further, isotope effect is studied for these targets and using various correlation analyses, dipole polarizability for ND and SiDx (x = 1–3) molecules are predicted.

Feshbach resonances of nonzero partial waves at different collision energies

Taking the ultracold 85Rb–87Rb collision system as an example, we investigated the Feshbach resonances of nonzero partial waves above the threshold. The self-energy at the threshold, which represents the coupling strength between open and closed channels, is considered a critical parameter to quantitatively describe the properties of Feshbach resonances. The total elastic and inelastic cross sections are calculated as functions of the magnetic field B and collision energy E col, ranging from 0.1 to 600 μK. For a large absolute value of the self-energy at the threshold, the resonance decays rapidly with increasing collision energy, and narrow resonances of nonzero partial waves can be clearly resolved in the contour plot of the inelastic cross section versus the collision energy and magnetic field. It was found that the resonance tail appeared at the given magnetic field when the cross section decreased from the maximal value of the resonance peak to the minimum value, where a long resonance tail indicates an appreciable resonance in a relatively large region of collision energy. This relationship between the self-energy and the properties of Feshbach resonances still exists in the thermally averaged inelastic rate coefficient. The bound-state energies for nonzero partial waves split owing to the spin–spin interaction, which results in multiple nearly-overlapping resonances. Both the spin–spin and second-order spin–orbit effects are included. However, multiple nearly-overlapping resonances for nonzero partial waves are difficult to resolve in thermally averaged rate coefficients.

Analytically solvable model of scattering of relativistic charged particles in solids

We propose an analytically solvable model of the differential and total inelastic cross sections, mean free paths, and energy losses of charged projectiles (electrons, positrons, protons, ions, etc) within a unified framework. It is applicable within a broad range of incident energies (from 30–50 eV up to GeV in a case of an electron). Only the optical data are used as an input, without any ad-hoc correction terms, splitting into close and distant collisions, or fitting and adjustable parameters. We demonstrate that the derived expressions are in a very good agreement with other more complex numerical models and experimental data. Application of the derived formulae greatly saves computational time of evaluation of cross sections with respect to the numerical integration required by other models.

Nucleon inelastic scattering cross sections on O16 and Si28

This paper reports cross-section measurements of the ($n,{n}^{\ensuremath{'}}$) and ($p,{p}^{\ensuremath{'}}$) reactions on $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$ at Geel Electron Linear Accelerator and at the 9-MV Tandem Accelerator of Horia Hulubei National Institute for Physics and Nuclear Engineering, respectively. The main purpose was to measure the neutron- and proton-induced inelastic $\ensuremath{\gamma}$-production cross sections for all observed transitions in $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, followed by the calculation of the corresponding total inelastic cross section. The results are compared with theoretical calculations performed using the talys 1.9 code, evaluated nuclear data, and previously reported experimental data. The broader goal of this work is to study whether and to what extent the neutron-induced inelastic cross sections of these nuclei can be inferred from those obtained using suitable charged particle reactions. We show that, by making use of the formal similarities between the neutron- and the proton-target optical model potentials and isospin symmetry in mirror nuclei, one can develop a procedure that combines experimental proton-induced inelastic cross sections with theoretical calculations to infer neutron inelastic cross sections. For $^{16}\mathrm{O}$ and $^{28}\mathrm{Si}$, the precision associated with this procedure is around 10--20% for most of the incident energy range.

New 23Na evaluation in the resolved resonance range taking into account both differential and double differential experiments

In 2012 CEA produced a entire new evaluation of sodium nuclear data for the release of the JEFF-3.2 evaluated nuclear data library. During the evaluation process performed with the CONRAD code, several differential measurements (total and discrete inelastic cross-sections) have been used. However double differential data (elastic angular distribution) that were yet available in the EXFOR database were not incorporated in the analysis at that time. The experimental elastic angular distribution were discarded because of it was impossible to obtain a good agreement for both angle-integrated cross-sections and double differential ones. The underlying cause of this disagreement is expected to be due to the attribution of quantum numbers to resonance and related channel amplitudes. Indeed these numbers are imposed during the analysis but impact differently angular distributions and angle-integrated cross-sections. An automated search for an accurate set of quantum numbers has been implemented in order to produce a reliable quantum numbers set. In this paper we present a new evaluation of Na-23 taking into account both differential and double differential measurements. The analysis performed with the CONRAD code reached the level of agreement with experimental data for the total and inelastic cross-sections but this time with a significant improvement for the elastic angular distributions. This new evaluation produced in the ENDF-6 format has then been tested and validated on critical facilities calculation (MASURCA and ZPPR) in different configurations (nominal and voided) in order to assess its performances.

Improved integrated nucleus-nucleus inelastic cross sections for light nuclides in Geant4

We propose a new root-mean-square radius parameterization for light nuclei A≤30 suitable for use in Geant4 calculations of nucleus-nucleus total hadronic inelastic scattering cross sections. The new approach takes into account the proton-neutron asymmetry of the reactants, and was fit to 360 measured total inelastic cross sections from the EXFOR database. Measured nuclear radii are better described in the new approach than the current Geant4 implementation, particularly for unstable nuclides, and there is better agreement with measured cross sections for both stable and unstable nuclides. The improved parameterization should help in carbon-ion therapy applications in particular.

Identification of characteristic features in scattering cross sections for the electrons colliding with silver, platinum, and gold atoms

A semi-relativistic approach is employed to calculate elastic differential, integral, and momentum transfer cross sections as well as total (elastic plus inelastic) cross sections for the scattering of electrons from silver, platinum, and gold atoms in the energy range 0.1–100 eV. The projectile-target interaction is composed of real (i.e. the sum of static, exchange, and polarization) and imaginary (i.e. absorption) potential. The total optical potential is then used in the solution of the Dirac equation for the scattered electrons. The characteristic features [Ramsauer-Townsend (RT) minimum and shape resonance] which are required for the fundamental understanding of the dynamic processes at the atomic level, are identified in the low energy region. The value of the RT minimum has been correlated with the scattering length to the dipole polarizability of the target atom. The calculated cross sections are compared with available theoretical calculations and experimental measurements in this energy region.

Scattering of e∓ from ytterbium atoms

The differential, total, momentum transfer and viscosity cross sections for the elastic scattering of electrons and positrons by ytterbium atoms have been calculated. We have also calculated the total inelastic and ionization cross sections. In addition, the Sherman function S(θ) and the inelastic mean free paths have been determined for the scattering of both projectiles. The critical minima in the elastic differential cross sections (DCS) were determined from the analysis of the DCS and S(θ). These investigations have been carried out within the framework of two different theoretical approaches at the impact energies 1 eV–0.5 GeV for both projectiles. In the atomic domain the solution involves a complex projectile-atom optical potential while in the nuclear domain only the nuclear potential has been employed. Both approaches employ the Dirac partial wave analysis. Our results are in reasonable agreement with available experimental data and other theoretical findings. To the best of our knowledge, for positron scattering, there are no experimental data available in the literature.

On a measurement approach to support evaluation of thermal scattering law data

Inelastic thermal neutron scattering in materials that act as neutron moderators, reflectors, and filters results in shaping the neutron spectrum at low energies. This phenomenon is described using differential scattering cross sections calculated from three components including the bound atom (i.e., nuclear) scattering cross section of the neutron, the ratio of the outgoing and incoming neutron energy, and the thermal scattering law (TSL), i.e., S(α,β), where α and β represent dimensionless momentum and energy exchange variables, respectively. To date, no TSL libraries are generated using measured data. However, valuable information may be derived from measurements and “targeted” experiments that can validate TSL data and the related inelastic scattering cross sections. As a demonstration, a suite of coordinated measurements and experiments is described that was designed and used to support the evaluation of the TSL for “nuclear” graphite. This experimental suite includes neutron powder diffraction (for structure analysis), positron annihilation (for nano porosity assessment), inelastic neutron scattering measurements using a chopper spectrometer, transmission experiments using neutrons with energy below the Bragg cutoff thereby accessing the total (inelastic) cross section, and a slowing-down-time experiment to observe the developing neutron spectrum in the material. This experimental suite was key to understanding the difference in TSL between “nuclear” and “ideal” graphite and for the inclusion of “nuclear” graphite in the ENDF/B-VIII.0 nuclear data library release.

Angle-Resolved Electron Scattering from H2O near 0°

An electron beam, characterized by a high-angular discrimination (≃0.7°), has been used to measure the total (elastic plus inelastic) cross section of H_{2}O in the energy range 3-100eV. Broad coincidence is found with recent experiments, including a pronounced shoulder in the 6-12eV region. However, at energies ≲6 eV, the present cross sections are ≃30% higher. Furthermore, forward scattering has been probed in the angular range 0°-3.5° and measures of the average (rotationally and vibrationally summed) differential elastic cross sections for incident energies ≤12 eV are obtained at a scattering angle ≃1^{∘}. The measurements, which provide the first test of theoretical predictions in an angular region experimentally unexplored until now, are found to be within 1 standard deviation of corresponding abinitio R-matrix calculations.

Three-quark force effect in proton\u2013proton scattering at 7, 8 and 13 TeV

Considering that the proton has an outer pion cloud of radius sim 0.87 fm and an inner core of radius sim 0.44 fm where the valence three quarks are confined and in the framework of optical limit approximation of Glauber, the proton–proton elastic scattering differential cross section, total cross section, the ratio of real part to imaginary part of elastic scattering amplitude in the forward direction, the total elastic and inelastic cross sections are calculated for LHC energy at sqrt{s}=7,;8,;13 TeV. The three-quark force is included. A good agreement is obtained with the experimental data at LHC energy 7, 8 and 13 TeV of last measurements of TOTEM Collaborations. Only for the differential cross section a disagreement is obtained for q^{2}>1;(mathrm{GeV}/c)^{2}, where the complete Glauber polynomial is needed. We tried to confirm the results of radii of two- and three-quark force and the gluon quant energy which were obtained before at ISR energy.

Calculation of electron scattering cross sections for Anthracene, Pyridine and Warfarin molecules over energy range 10–30000 eV

This paper reports electron impact total cross section, total elastic, total inelastic and differential cross sections for molecules Anthracene, Pyridine and Warfarin having been computed using the independent atom model with screening-corrected additivity rule over an incident energy range of 10–30000 eV. The calculations are performed with relativistic (Dirac) partial-wave for scattering by applying a local central interaction potential V(r). A model spherical complex optical potential is used for calculations. Good agreement is achieved in intermediate and high-energy zones.

Electron impact total ionization cross sections of diboranes - B2H4 and B2H6

We report calculated total ionization cross sections of diborane molecules (B2H4 and B2H6) from threshold to ∼2 keV by two methods viz., Complex Scattering Potential-ionization contribution (CSP-ic) and Binary Encounter Bethe (BEB) formulations. In the CSP-ic method, total ionization cross sections Qion are extracted from total inelastic cross sections denoted by Qinel. In BEB, the Qion are obtained as the sum of molecular orbital cross sections. The results obtained through both methods are compared and are found to be in good mutual accord (except the atomic-sum estimate on B2H6), but both the theoretical results differ considerably from only available measurement on B2H6. There are no previous data for B2H4. Comparisons with corresponding hydrocarbon molecules are also afforded. Our work suggests fresh measurements on B2H6 and new experiments on B2H4.

Electron interactions with astro chemical compounds

In present work electron induced processes with important astro-compounds found in the tholins of Titan are investigated. We report calculated total elastic cross sections Qel, total inelastic cross sections Qinel, total ionization cross sections Qion, total excitation cross sections ∑Qexc and total cross sections QT for hydrogen cyanide (HCN), cyanoacetylene (HCCCN), vinyl cyanide (CH2CHCN), methanimine (CH2NH) and ethanimine (CH3CHNH) on electron impact for energies from ionization threshold to 5 keV. We have employed the Spherical Complex Optical Potential (SCOP) formalism to investigate elastic as well as inelastic processes and used Complex Scattering Potential – ionization contribution (CSP-ic) method to derive ionization cross sections. In absence of any theoretical or experimental data of ionization cross sections except for HCN and HCCCN, we have computed Qion using the Binary- Encounter- Bethe (BEB) method for all these molecules and have found reasonable agreement. This is the maiden attempt to report various total cross sections for all these astro-molecules except HCN and HCCCN.