Elastic Cross Research Articles

Elastic and Inelastic Cross Sections for Low-Energy Electron Collisions with ClF Molecule Using the R-Matrix Method

The ClF molecule belongs to an interhalogen family and is important in laser physics and condensed phase molecular dynamics. The elastic and excitation scattering cross sections are obtained in a fixed nuclei approximation using the UKRmol+ codes based on R-matrix formalism. The scattering calculations were performed in the static-exchange (SE), static-exchange-plus-polarisation (SEP), and close-coupling (CC) models. Three CC models with different target states were employed, namely, the 1-state, 5-states, and 12-states. In the CC model, the target states were represented by configuration interaction (CI) wavefunctions. A good agreement of dipole and quadrupole moments of the ground state was obtained with the experimental values, which indicates a good representation of the target modelling. The study predicted the existence of a shape resonance in the SE, SEP, and 5-states CC models. This resonance vanished in the 12-states CC model. The excitation cross sections from ground to the lowest two excited states were also reported. The elastic differential and momentum transfer cross sections were obtained in the 12-states CC models. The contribution of long-range interactions to elastic scattering was included via Born closure approach. The quantities like collision frequencies and rate coefficients were also presented over a wide range of electron temperatures. The ionization cross sections were computed using the binary-encounter-Bethe (BEB) model. The results were reported in C2v point group representation.

Unitarisation dependence of diffractive scattering in light of high-energy collider data

We study the consequences of high-energy collider data on the best fits to total, elastic, inelastic, and single-diffractive cross sections for pp and poverline{p} scattering using different unitarisation schemes. We find that the data are well fitted both by eikonal and U-matrix schemes, but that diffractive data prefer the U-matrix. Both schemes may be generalised by means of an additional parameter; however, this yields only marginal improvements to the fits. We provide estimates for ρ, the ratio of the real part to the imaginary part of the elastic amplitude, for the different fits. We comment on the effect of the different schemes on present and future cosmic ray data.

Relativistic study on the scattering of electrons and positrons from atomic iron at energies 1 eV – 10 keV

This paper reports on the differential, integral, momentum transfer and viscosity cross sections along with spin polarisation for elastically scattered electrons and positrons from iron atoms in the incident energy () range eV. In addition, we report here systematically the details of the critical minima in the elastic differential cross sections, and the absorption and total cross sections. An optical model using a complex optical potential, composed of static, exchange, polarisation and imaginary terms, is used to solve the Dirac relativistic equation in partial-wave analysis. A comparison of our evaluated cross sections with the available experimental data and other theoretical findings shows a reasonable agreement over the studied energy range.

Three-nucleon force effects in the FSI configuration of the d(n, nn)p breakup reaction

We investigated three-nucleon (3N) force effects in the final state interaction (FSI) configuration of the d (n,nn) pd(n,nn)p breakup reaction at the incoming nucleon energy E_nEn= 200 MeV. Although 3N force effects for the elastic nucleon-deuteron scattering cross section at comparable energies are located predominantly in the region of intermediate and backward angles, the corresponding 3N force effects for the integrated FSI configuration breakup cross section are found also at forward scattering angles.

Analytical Expressions for the Differential Elastic Scattering Cross Sections of Nonidentical Nuclear Particles with Channel Spin 1 and 2

In this paper, general analytical expressions are obtained for the differential elastic scattering cross sections of two nuclear particles with allowance for spin-orbit splitting for channels with the half-integer spins 3/2 and 5/2, which are parameterized with respect to the orbital quantum number l. This representation makes it possible to take into account explicitly a definite, energy-dependent number of scattering partial waves and to consider the relative contribution of each partial wave. The obtained expressions can be used when performing phase shift analysis in elastic scattering of nonidentical particles, for example, N2H, N6Li, 2H7Li, and 2H9Be at low energies.

Analytical Expressions for the Differential Elastic Scattering Cross Sections of Nonidentical Nuclear Particles with Channel Spins 3/2 and 5/2

Analytical Expressions for the Differential Elastic Scattering Cross Sections of Nonidentical Nuclear Particles with Channel Spins 3/2 and 5/2

Coherent and Incoherent Elastic Photoproduction of π0 Meson on Light Nuclei

The paper presents calculations of the cross sections of the elastic photoproduction for π0 meson on 6Li, 7Li and 9Be nuclei in terms of the impulse approximation using the intermediate coupling p-shell model. Measurements are performed in the excitation energy region of Δ(1232)3/2+ resonance. The algorithm of the cross section selection is proposed for γ7Li → π07Li reaction. These calculation results are in good agreement with the experimental data on the elastic photoproduction cross sections for π0 meson on 7Li nucleus obtained by other authors [2].

Quantum-Mechanical Theory of Elastic Scattering and Cross Section Determination of Particle Interactions in Plasma

A quantum-mechanical description of the theory of elastic scattering and a technique for determining the cross sections of particle interactions in plasma are described. An asymptotic solution of the Schrodinger equation for the elastic interaction of plasma particles is presented. Algorithms for determining phase shifts based on the Modified Effective Range Theory (MERT) are given. The Born approximation is considered to determine the amplitude of the scattered waves and the scattering cross section of the particles. Data are presented on the cross sections for scattering of electrons by atoms and ions in argon.

Several Effects Unexplained by QCD

Several new experimental discoveries in high energy proton interactions, yet unexplained by QCD, are discussed in the paper. The increase of the cross sections with increasing energy from ISR to LHC, the correlation between it and the behavior of the slope of the elastic diffraction cone, the unexpected increase of the survival probability of protons in the same energy range, the new structure of the elastic differential cross section at rather large transferred momenta (small distances) and the peculiar ridge effect in high multiplicity inelastic processes are still waiting for QCD interpretation and deeper insight in vacuum.

Elastic Scattering of Mo-Mo, Mo-S and S-S Atomic Pairs in the Relative Kinetic Energy Range of 2–200 eV

The interatomic binary potentials of Mo-Mo, Mo-S and S-S, approved by Molecular Dynamics, were used to calculate elastic phase shifts and cross sections of the atomic pairs in the relative kinetic energy range of 2–200 eV. It is expected the obtained differential and integral cross sections to be of help to describe sputtering of MoS2 nanometer layers in design of perspective devices of nanoelectronics and photonics.

Correlation between left main coronary artery bifurcation angle and non-calcified plaque and its hydrodynamics

Objective To investigate the correlation between the angle and distribution of non-calcified plaque of left main coronary bifurcation and its hydrodynamic theory. Methods Retrospective analysis of 55 patients suspected of coronary heart disease who had undergone coronary computed tomographic angiography from January 2014 to June 2016. Angle, quadrant distribution, distance from bifurcation reference plane, minimal lumen area and extravascular elastic membrane cross section area of left main coronary bifurcation were measured. Then we calculated the plaque burden. The left main coronary bifurcation lesions were divided into plaque group and non-plaque group. Student's t test was used to compare the two groups.The left main coronary bifurcation lesions were divided into ≥70° group and<70° group, Chi-square test and Fisher exact test were used to compared the two groups. Pearson correlation analysis was used to analyse the bifurcation angle and plaque distance. The data of non-plaque group was imported into the MIMICS,3-MATIC and abaqus CFD software to establish the hydrodynamic model, which was used to analyze the changes of pressure and velocity at different angles. Results Plaque group has 25 patients whose average value of the bifurcation angle was (55.95±14.77)°;non-plaque group has 30 patients whose average value of the bifurcation angle was(55.95±14.77)°.Angle difference was statistically significant between plaque and non-plaque group(t=2.893, P=0.006);Plaque difference was statistically significant between ≥70° and<70° groups. The distance was negatively correlated with bifurcation angle(r=-0.773, P<0.001). Following the increase of bifurcation angle, the vascular wall area of high pressure and low speed region growed The green region of low-wall pressure with irregular distribution appeared in the lateral wall of the vessel that opposite to the red region of the bifurcation, and this region had lager gradient variability of wall pressure. Conclusion With the increase of coronary bifurcation angle, the possibility of plaque formation increases, the distance from plaque to bifurcation increases,the plaques tend to appear in the lateral wall of the blood vessels. Key words: Coronary vessels; Tomography, X-ray computed; Hydrodynamic

Collision cross sections and transport coefficients of O−, O2−, O3− and O4− negative ions in O2, N2 and dry air for non-thermal plasmas modelling

The ions interaction data such as interaction potential parameters, elastic and inelastic collision cross sections and the transport coefficients (reduced mobility and diffusion coefficients) have been determined and analyzed in the case of the main negative oxygen ions (O−, O2−, O3− and O4−) present in low temperature plasma at atmospheric pressure when colliding O2, N2 and dry air. The ion transport has been determined from an optimized Monte Carlo simulation using calculated elastic and experimentally fitted inelastic collision cross sections. The elastic momentum transfer collision cross sections have been calculated from a semi-classical JWKB approximation based on a (n−4) rigid core interaction potential model. The cross sections sets involving elastic and inelastic processes were then validated using measured reduced mobility data and also diffusion coefficient whenever available in the literature. From the sets of elastic and inelastic collision cross sections thus obtained for the first time for O3−/O2, O2−/N2, O3−/N2, and O4−/N2 systems, the ion transport coefficients were calculated in pure gases and dry air over a wide range of the density reduced electric field E/N.

Singular lensing from the scattering on special space\u2013time defects

It is well known that certain special classes of self-gravitating point-like defects, such as global (non gauged) monopoles, give rise to non-asymptotically flat space–times characterized by solid angle deficits, whose size depends on the details of the underlying microscopic models. The scattering of electrically neutral particles on such space–times is described by amplitudes that exhibit resonant behaviour when thescattering and deficit angles coincide. This, in turn, leads to ring-like structures where the cross sections are formally divergent (“singular lensing”). In this work, we revisit this particular phenomenon, with the twofold purpose of placing it in a contemporary and more general context, in view of renewed interest in the theory and general phenomenology of such defects, and, more importantly, of addressing certain subtleties that appear in the particular computation that leads to the aforementioned effect. In particular, by adopting a specific regularization procedure for the formally infinite Legendre series encountered, we manage to ensure the recovery of the Minkowski space–time, and thus the disappearance of the lensing phenomenon, in the no-defect limit, and the validity of the optical theorem for the elastic total cross section. In addition, the singular nature of the phenomenon is confirmed by means of an alternative calculation, which, unlike the original approach, makes no use of the generating function of the Legendre polynomials, but rather exploits the asymptotic properties of the Fresnel integrals.

Propagation of Uncertainties of the Nucleon-Nucleon Potential to the Neutron-Deuteron Elastic Scattering Cross Section

Faddeev formalism is used to study the propagation of theoretical uncertainties from the two-nucleon force to three-nucleon scattering observables. Predictions are obtained with the One-Pion-Exchange Gaussian interaction, for which correlations between its parameters are known. Within the Monte Carlo approach we are able to estimate uncertainties of three-nucleon observables arising from the imprecise knowledge of the One-Pion-Exchange Gaussian potential parameters. We found that the uncertainties of this type are small for three-nucleon elastic scattering cross section at investigated here energies up to the nucleon laboratory energy of 200 MeV. They remain smaller than the dominant theoretical uncertainty arising from using various models of nucleon-nucleon interactions. We also compare the above-mentioned results with other types of theoretical uncertainties, that is with the ones stemming from order truncation errors and regulator dependencies, present in calculations based on the chiral interaction.

Low-energy positron collisions with CH2O⋯ H2O complexes

We present calculated elastic integral cross section (ICS) for low-energy positron scattering by formaldehyde-water complexes (hydrogen-bonded pairs CH2O⋯ H2O). We considered four different structures for the complex obtained by classical Monte Carlo simulations in water environment at room temperature. We also present results for formaldehyde in gas phase. The calculations used the Schwinger multichannel method and were carried out in the static-polarization level of approximation, for energies from 0.5 eV to 10 eV. We also employed the Born-closure procedure to account for the long range potential due to the permanent dipole moment of the complexes and the formaldehyde molecule. We compared our results obtained in gas and liquid phases to investigate the effect of microsolvation in the ICS. We also compared our results for the formaldehyde molecule with the results available in the literature.

Abstract ID: 88 Quantum versus classical Monte Carlo simulation of low energy electron transport in condensed media

Purpose Monte Carlo simulations are being applied to study radiation interactions and energy deposition on sub-micron length scales within cells, e.g., DNA, in diverse contexts across medical physics. While these classical trajectory Monte Carlo simulations ignore the quantum wave nature of the electron, quantum effects may become non-negligible as electron energy decreases below 1 keV, with electron wavelength becoming considerable relative to the size of biological targets. This work investigates quantum mechanical (QM) treatments of low energy electron transport in condensed media and compares results with those from the corresponding classical trajectory Monte Carlo (MC) model. Methods For QM calculations, a simplified model of electron transport in water is developed consisting of a plane wave (representing an electron) incident on a collection of ∼103 point scatterers (molecules) representing a water droplet. Scatterer positions are random but are constrained by a minimum scatterer-to-scatterer separation, dmin, in some simulations. Cross sections for isotropic elastic and inelastic (absorption) interactions are varied. QM calculations involve numerically solving the system of ∼103 coupled equations for the electron wavefield incident on each scatterer. Results are averaged over 105 droplets with different point scatterer positions but otherwise same parameters (incident electron energy, cross sections). Average QM droplet incoherent cross sections and scattering event densities are compared with analogues computed within the corresponding classical MC model, and estimates of relative errors on MC results are computed. Results Relative errors on MC results vary with electron wavelength, droplet shape and structure (dmin), and interaction cross section. Relative errors on droplet differential cross sections generally differ from errors on scattering event density. The introduction of inelastic scatter generally increases relative errors (compared to calculations with the same elastic scatter cross section) with some exceptions (e.g. longer wavelength, relatively large inelastic cross section). Accounting for structure (non-zero dmin) enhances differences between QM and MC results. Conclusions The quantum wave nature of electrons may be non-negligible for simulations of electron transport within small-scale biological targets. Future work will involve the development of more realistic models of electron transport in condensed media.

Low energy cross sections for electron scattering from tetrafluoroallene

We report elastic, total, excitation, differential and momentum-transfer cross sections for scattering of low-energy electrons by tetrafluoroallene (C3F4) using the close-coupling (CC) approximation in the R-matrix method with Quantemol-N. We have tested various target models initially to check for the convergence of the result and the final results are provided with the best target model. We have detected shape resonances of symmetry 2 E(2B1,2B2) at 3.08 eV and 3.71 eV with a close-coupling and static exchange models which is seen as a sharp feature in the elastic and momentum transfer cross sections. We also detected other resonances of symmetry 2 E at 11.26 eV and of symmetry 2A2 at 11.12 eV below the ionization threshold of the target respectively. The present elastic and total cross sections are compared with the elastic and total cross sections of allene (C3H4), propene (C3H6) and hexafluoropropene (C3F6) as there were no results available for C3F4. The effect of fluorination is clearly seen with the shape resonance for C3F4 getting slightly shifted to higher energies compared to allene. Finally, we also report the ionization cross section calculated using the Binary-Encounter Bethe (BEB) method. The present calculation is a maiden attempt to find cross sections for C3F4 molecule which could be useful for fluorocarbon plasma modeling.

Electron collisions with F2CO molecules

In this paper we present elastic differential, integral, and momentum-transfer cross sections for electron collisions with carbonyl fluoride $({\mathrm{F}}_{2}\mathrm{CO})$ molecules for the incident electron's energy from 0.5 eV to 20 eV. The Schwinger multichannel method with pseudopotentials was employed to obtain the cross sections in the static-exchange and static-exchange plus polarization approximations. The present results were compared with the available data in the literature, in particular, with the results of Kaur, Mason, and Antony [Phys. Rev. A 92, 052702 (2015)] for the differential, total, and momentum-transfer cross sections. We have found a ${\ensuremath{\pi}}^{*}$ shape resonance centered at 2.6 eV in the ${B}_{1}$ symmetry and other resonance, in the ${B}_{2}$ symmetry, located at around 9.7 eV. A systematic study of the inclusion of polarization effects was performed in order to have a well balanced description of this negative-ion transient state. The effects of the long-range electric dipole potential were included by the Born closure scheme. Electronic structure calculations were also performed to help in the interpretation of the scattering results, and associate the transient states to the unoccupied orbitals.

Elastic $qq$ Cross Sections at Finite Chemical Potential in the Nambu--Jona-Lasinio Lagrangian

We discuss the elastic qq cross sections at finite chemical potential in the Nambu–Jona-Lasinio model. We comment the generic features of the cross sections as functions of the chemical potential, temperature and collision energy. Finally, we discuss their relevance in the construction of a relativistic transport model for heavy-ion collisions based on this effective Lagrangian.

On the feasibility to perform integral transmission experiments in the GELINA target hall at IRMM

Shielding experiments are relevant to validate elastic and inelastic scattering cross sections in the fast energy range. In this paper, we are focusing on the possibility to use the pulsed white neutron time-of-flight facility GELINA to perform this kind of measurement. Several issues need to be addressed: neutron source intensity, room return effect, distance of the materials to be irradiated from the source, and the sensitivity of various reaction rate distributions through the material to different input cross sections. MCNP6 and TRIPOLI4 calculations of the outgoing neutron spectrum are compared, based on electron/positron/gamma/neutron simulations. A first guess of an integral transmission experiment through a 238 U slab is considered. It shows that a 10 cm thickness of uranium is sufficient to reach a high sensitivity to the 238 U inelastic scattering cross section in the [2-5 MeV] energy range, with small contributions from elastic and fission cross sections. This experiment would contribute to reduce the uncertainty on this nuclear data, which has a significant impact on the power distribution in large commercial reactors. Other materials that would be relevant for the ASTRID 4th generation prototype reactor are also tested, showing that a sufficient sensitivity to nuclear data would be obtained by using a 50 to 100cm thick slab of side 60x60cm. This study concludes on the feasibility and interest of such experiments in the target hall of the GELINA facility.