Low-energy electron scattering with H2O and NH3 molecules.

Purpose: We describe here a novel full-differential Monte Carlo (MC) event-by-event simulation, for modelling electron and positron histories in liquid and gaseous water, with impact energies ranging from the water excitation threshold (7.4 eV) to 10 keV. This new track-structure code is named EPOTRAN, an acronym for Electron and POsitron TRANsport in water. Material and methods: All the processes induced by both electrons and positrons are studied in detail via theoretical differential and total cross sections, calculated within the quantum mechanical framework by using the partial-wave method. Elastic and inelastic interactions are then successively reviewed, including in particular an original description of the positron-induced capture process leading to Positronium formation. Results: Total and differential cross sections are reported and compared with a large set of existing measurements. Rather good agreement is generally observed over the considered energy range. Conclusions: This work reports the theoretical cross sections used in a special purpose Monte Carlo simulation suitable for electron and positron transport in gaseous and liquid water. This MC code should represent an accurate tool for dose calculation at the nanometric scale, by providing a detailed spatial distribution of energy deposits. Furthermore, positron trajectory studies made possible by this approach should prove useful for evaluating the real contribution of the positron range on the overall spatial resolution of PET (Positron Emission Tomography) imaging.

We report calculated total elastic cross sections Qel, total ionisation cross sections, Qion, summed total excitation cross sections ∑Qexc and total cross sections QT for CH3SH upon electron impact for energies from ionisation threshold to 5 keV. We have employed Spherical Complex Optical Potential (SCOP) formalism to calculate total elastic cross section Qel, and total inelastic cross section Qinel and used Complex Scattering Potential – the ionisation contribution (CSP-ic) method to extract the ionisation cross sections, Qion, from the calculated Qinel. The calculated total cross sections are examined as functions of incident electron energy and are compared with available data wherever possible and overall good agreement is observed. In this work Qel, Qion, and ∑Qexc are reported for the first time for CH3SH in this energy range.

(e,2e) ionization cross-sections for C4H4O, C4H8O and C6H8O

New evaluations of the neutron cross sections for 14N and 16O have been made for ENDF/B-VI. The evaluations are based at low energies on R-matrix analyses of reactions in the 15N and 17O systems, and at higher energies on GNASH calculations and experimental data evaluations, including covariance analyses. The 15N system R-matrix analysis includes data from reactions among the channels n+14N, p+14C, and α+11B at energies corresponding to excitations in 15N below Ex=13 MeV. The resonance structure of all cross sections in this energy range is fairly well reproduced. New data indicate a different J-value for the first resonance, however. Sub-threshold S-wave levels required to explain the large n+14N total and elastic cross sections near zero energy give scattering lengths that differ significantly from the previous values. The R-matrix analysis of the 17O system includes many new measurements of the n+16O total cross section, done primarily at Oak Ridge and at Karlsruhe. The resonance structure of all the cross sections [total, (n,n), (n,α), and (α,α)] is well represented by the fit in the region below En = 6.5 MeV. The new total cross section information gives different positions for some of the resonances and implies a different normalization for the (n,α) cross sections than that obtained in the ENDF/B-IV analysis. The evaluations at energies above the ranges of the R-matrix analyses incorporate results from a number of experiments performed since the previous ENDF/B evaluations. Especially important are new measurements of the total cross sections and differential elastic, inelastic, and gamma-ray production cross sections.

We study the positron--nitrogen-molecule scattering process under the rovibrational coupling method to include the effect of rotational and vibrational motion of the nuclei dynamically during the scattering process. Here we compute the angle integrated elastic and (state-to-state) rotational excitation, elastic and (state-to-state) vibrational (summed over rotational) excitation, and total (summed over rotational and vibrational) cross sections for the incident positron energy between 0.0 and 10 eV. However, in present paper we concentrate our discussion on the results in the lower-energy region, especially below 3.0 eV. To calculate the cross sections we use the model correlation polarization potential to include the distortion effect of the target electronic state in the presence of the positron. The calculated total cross sections are compared with the theoretical calculations and experimental results. The present theoretical results agree quite well with the recent theoretical and measured values. The vibrational and rotational elastic and excitation cross sections are also compared with the existing theoretical results. The state-to-state potential coupling and dynamical coupling effects on different cross sections are studied.

The elastic proton-helium differential cross section has been determined for incident laboratory energies from 45 to 400 GeV in the range $0.003\ensuremath{\le}|t|\ensuremath{\le}0.52$ (${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ by means of the internal-gas-jet-target technique. The differential cross section drops 4-5 orders of magnitude to the first dip at $|t|\ensuremath{\simeq}0.22$ (${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. The shrinkage in the slope of the differential cross section is found to be twice as fast as that in the proton-proton case. The slope parameter at $|t|\ensuremath{\simeq}0$ is described by the formula $b=24+1.13\mathrm{ln}s$, where $b$ is in (${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{\ensuremath{-}2}$ and $s$ is in ${\mathrm{GeV}}^{2}$. The elastic proton-helium cross section is normalized to the known elastic proton-proton cross section using data taken with a helium and hydrogen mixture as a target. The proton-helium total cross section is determined from the optical theorem. The total cross section rises by 4% between 100 and 400 GeV. Results are presented on the real part of the elastic-scattering amplitude and on the total elastic cross section. The experimental differential cross sections are compared to Glauber-model predictions.

An experiment has been carried out to examine the inelastic nuclear interaction properties of high-energy electrons and muons in emulsion. A study was made of interactions produced by 10.5-GeV muons and 10.0- and 16.0-GeV electrons. Total and differential cross sections have been measured and compared with calculations carried out with the formulation of Hand and Wilson for inelastic lepton scattering. On the basis of the calculations, the ratio of electron to muon total cross sections was found to be 3.5:1, whereas experimentally the ratio was measured to be 2.18\ifmmode\pm\else\textpm\fi{}0.40 for the 10-GeV leptons. To explain the total cross section for electrons, an average scalar-photon contribution equal to 12% of the transverse-photon cross section is needed, which is consistent with other experiments. The muon cross section was found to be significantly larger than expected, and it cannot be explained by a similar scalar-photon contribution. The energy dependence of the total cross sections is in agreement with theory, as are the angular distributions of the scattered leptons.

We report electron impact total cross sections, Q(T), for e-N(2)O scattering over an extensive range of impact energies approximately from 0.1 eV to 2000 eV. We employ an ab initio calculation using R-matrix formalism below the ionization threshold of the target and above it we use the well established spherical complex optical potential to compute the cross sections. Total cross section is obtained as a sum of total elastic and total electronic excitation cross sections below the ionization threshold and above the ionization threshold as a sum of total elastic and total inelastic cross sections. Ample cross section data for e-N(2)O scattering are available at low impact energies and hence meaningful comparisons are made. Good agreement is observed with the available theoretical as well as experimental results over the entire energy range studied here.

We calculate total hadron-hadron cross sections at high energies using the Low-Nussinov two-gluon model of the Pomeron. The gluon exchange is represented by a phenomenological potential including screened color-Coulomb, screened confining, and spin-spin interactions. We use bound-state wave functions obtained from a potential model for mesons, and a Gaussian wave function for a proton. We evaluate total cross sections for collisions involving pion, kaon, rho, phi, D, J/psi, psi', Upsilon, Upsilon', and the proton. We find that the total cross sections increase with the square of the sum of the root-mean square radii of the colliding hadrons, but there are variations arising from the spin-spin interaction. We also calculate the total cross sections of a mixed-color charmonium state on a pion and on a proton. The dependence of the total cross section on the size and the color state of the charmonium is investigated.

This work includes the determination of the differential cross sections (DCSs), total cross sections (TCSs), and momentum transfer cross sections (MTCSs) for electron scattering by potassium atoms, as well as the derivation of the spin polarisation parameter S (). These calculations are made to describe the interaction between an electron and a target atom in the energy range (5–500 eV). Theoretical work was done by combining the static potential with the polarisation potential over large distances and the Perdew -Zunger correlation potential over short ones. "The total results show close agreement when compared to the experimental and theoretical conclusions provided by the others".

A theoretical analysis of the collisions of particles with deuterons is carried out in the high-energy approximation. This approximation, which corresponds to a generalized form of diffraction theory, takes explicit account of double collision processes as well as single ones. It is used to express the amplitudes for elastic and inelastic scattering by deuterons in terms of the elastic-scattering amplitudes of the neutron and proton and the deuteron wave functions. The resulting expressions are used to evaluate the differential cross section for elastic scattering, and the angular distribution of inelastic scattering (i.e., the differential cross section for deuteron breakup integrated over final energies of the incident particle). The contributions to these cross sections of the various single and double scattering processes and the terms which represent their interference are exhibited individually. Expressions are derived for the total cross section of the deuteron and for its elastic and inelastic total scattering and absorption cross sections. The difference between the various types of deuteron cross sections and the sum of the corresponding cross sections for the free neutron and proton is explained in some detail. Spin-dependent interactions are treated, and for incident particles of spin \textonehalf{} an expression is given for the deuteron total cross section in terms of the general spin-dependent scattering amplitudes of the neutron and proton. The theory is applied to antiproton-deuteron collisions in the energy range from 0.13 to 17.1 BeV. The results for the total and absorption cross sections which are calculated for a variety of models of the deuteron wave function are found to be in good agreement with the measurements. The magnitudes of such effects as double scattering and the interference of single-and double-scattering amplitudes are seen to be appreciable.

We present a theoretical study of the ionization of nitrogen atom by a singly charged sodium ion using the classical trajectory Monte Carlo method. Although we suffer from a lack of cross section data of this collision system, the knowledge of the basic cross sections is essential in fusion science, because this reaction has potential applications in the diagnostic of magnetically confined fusion plasmas. In our investigations, the Na+–N collision system is reduced to a three-body problem. The interaction between the collision partners is described by the Garvey-type model potential. The results of our study provide insight into the dynamics of singly charged sodium–nitrogen interactions. The total cross sections are presented in the impact energy range between 10 keV and 10 MeV and compared them with the available experimental data. The single and double differential cross sections are presented at 30, 40, 50 and 60 keV energies related to the energies of the plasma diagnostic used in the nuclear fusion.

Electron-impact cross sections for excitation of the 7 $^{2}$${\mathit{S}}_{1/2}$, 8 $^{2}$${\mathit{S}}_{1/2}$, 5 $^{2}$${\mathit{D}}_{3/2}$, and 6 $^{2}$${\mathit{D}}_{3/2}$ states of rubidium have been measured from threshold to 1000 eV. The optical-excitation-function method has been employed in a crossed atom- and electron-beam apparatus. Relative, total (cascade including) experimental cross sections are made absolute by comparison with the known total cross section of the Rb D1 line. Total excitation cross sections are compared with theoretical calculations employing first Born approximation and theoretical branching ratios. Born cross sections for the 7 $^{2}$${\mathit{S}}_{1/2}$ and 8 $^{2}$${\mathit{S}}_{1/2}$ states are obtained from the literature, while Born cross sections for the 5 $^{2}$${\mathit{D}}_{3/2}$, 6 $^{2}$${\mathit{D}}_{3/2}$, and all cascading states are calculated in this paper. At high energies, the measured total $^{2}$${\mathit{D}}_{3/2}$ state cross sections show 1/E behavior and converge to first Born theory; for Eg100 eV, experiment and theory agree within 6.7% for 5 $^{2}$${\mathit{D}}_{3/2}$ and within 3.7% for 6 $^{2}$${\mathit{D}}_{3/2}$. The total cross sections for the $^{2}$${\mathit{S}}_{1/2}$ states do not converge to Born theory even at 1000 eV, and it is shown that this cannot be attributed to cascading. At low energies, $^{2}$${\mathit{S}}_{1/2}$ and $^{2}$${\mathit{D}}_{3/2}$ state total excitation cross sections have similar shapes with sharply peaked maxima at about 0.9 eV above threshold. After cascading is corrected using first Born theory, estimated experimental cross sections for direct excitation of higher fine-structure states of rubidium are given.

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.

We report normalized experimental and theoretical differential cross sections for elastic electron scattering by ${\mathrm{C}}_{4}$H${}_{4}$O (furan) molecules from a collaborative project between several Brazilian theoretical groups and an experimental group at California State Fullerton, USA. The measurements are obtained by using the relative flow method with helium as the standard gas and a thin aperture target gas collimating source. The relative flow method is applied without the restriction imposed by the relative flow pressure condition on helium and the unknown gas. The experimental data were taken at incident electron energies of 1, 1.5, 1.73, 2, 2.7, 3, 5, 7, 10, 20, 30, and 50 eV and covered the angular range between ${10}^{\ifmmode^\circ\else\textdegree\fi{}}$ and ${130}^{\ifmmode^\circ\else\textdegree\fi{}}$. The measurements verify observed ${\ensuremath{\pi}}^{*}$ shape resonances at $1.65\ifmmode\pm\else\textpm\fi{}0.05$eV and $3.10\ifmmode\pm\else\textpm\fi{}0.05$ eV scattering energies, in good agreement with the transmission electron data of Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004)]. Furthermore, the present results also indicated both resonances dominantly in the $d$-wave channel. The differential cross sections are integrated in the standard way to obtain integral elastic cross sections and momentum transfer cross sections. The calculations employed the Schwinger multichannel method with pseudopotentials and were performed in the static-exchange and in the static-exchange plus polarization approximations. The calculated integral and momentum transfer cross sections clearly revealed the presence of two shape resonances located at 1.95 and 3.56 eV and ascribed to the ${B}_{1}$ and ${A}_{2}$ symmetries of the ${C}_{2v}$ point group, respectively, in very good agreement with the experimental findings. Overall agreement between theory and experiment regarding the differential, momentum transfer, and integral cross sections is very good, especially for energies below 10 eV.