Collision cross-sections for scattering of electrons from NO molecule

Electron-NO scattering is investigated in the energy range 2–1000eV by using a parameter-free spherical complex optical potential (SCOP) approach in the fixed nuclei approximation. The real part of the optical potential consists of three potentials namely, the static, the exchange and the polarization. For the imaginary part of the SCOP, we employ a semi-empirical model absorption potential. The molecular charge density function is calculated from a single-configuration molecular orbital based on Slater type orbitals. The various potential terms are then determined from these charge density functions. Calculations of the elastic (with and without absorption effects), total absorption, momentum transfer and differential cross-sections are obtained and compared with the available theoretical results and experimental measurements.     

Studies on vibrational excitation differential cross-sections of low-energy electron scattering from N2 molecule

The vibrational excitation differential cross-sections (DCS) of low-energy electron-N₂ scattering are studied using vibrational close-coupling (VCC) method and vibrational scattering potentials which include static, exchange and polarization contributions. By including the contributions of 18 partial waves, 20 vibrational states, and 16 molecular symmetries (up to Λ=7), the converged vibrational excitation (0↦2, 0↦3, 0↦4) DCS agree well with experimental results. Also obtained are converged vibrational (1↦0, 1↦1, 1↦2, 1↦3) DCS, with the impact energies being those of the main resonant peaks (1.92 eV, 1.90 eV, 1.62 eV, 1.63 eV).     

Low frequency vibrations of 1,3-butadiene, 1,3-butadiene-d4, and 1,3-butadiene-d6

The absorption bands in the far infrared due to the torsional and in-plane skeletal bending vibrations have been examined in detail together with some mid-infrared bands. Torsional energy level spacings up to v₁₃ = 5 for butadiene and up to v₁₃ = 4 and 3, respectively, for the d₄- and d₆-compounds have been measured accurately, and the data used to investigate the nature of the potential function for rotation about the CC single bond. A Coriolis interaction between the torsion and the in-plane bending mode ν₂₄ has been analyzed in detail.     

One century of experiments on electron-atom and molecule scattering: A critical review of integral cross-sections

La Rivista del Nuovo Cimento -     

Dipole oscillator strengths for the photoabsorption,photoionization and fragmentation of molecular oxygen

The photoabsorption, photoionization and fragmentation of O₂ have been studied using electron impact coincidence methods to obtain branching ratios and dipole oscillator strengths (cross-sections). The photoabsorption measurements cover the energy range 5–300 eV while the formation of electronic states of O₂⁺ (photoelectron spectroscopy) and the resulting ionic fragmentation (photoionization mass spectrometry) are both measured from close to threshold up to photon energies of 75 eV. The binding energy spectra of O₂ show peaks at 33, 47 and 57 eV in addition to those reported elsewhere in the literature. These peaks are assigned to multiple final ion states arising from photoionization of the inner valence orbitals. Structure in the O₂⁺ electronic state partial oscillator strength curves is in good agreement with recent theoretical work which predicts the existence of several shape resonances. A quantitative picture of the dipole-induced breakdown of O₂ is obtained for the energy range 12–75 eV. The photoionization efficiency is found to be constant above 20 eV.     

Polycyclic aromatic hydrocarbons from the co-pyrolysis of catechol and 1,3-butadiene

In order to better understand the reactions responsible for the formation and growth of polycyclic aromatic hydrocarbons (PAH) from solid fuels, we have performed pyrolysis experiments in an isothermal laminar-flow reactor (at temperatures of 600-1000 °C and a fixed residence time of 0.3 s) with catechol, a model fuel representative of the aromatic moieties in coal and biomass fuels; 1,3-butadiene, a major product of biomass pyrolysis; and with catechol and 1,3-butadiene together (in a catechol-to-1,3-butadiene molar ratio of 0.83). No PAH of ?3 rings are produced at temperatures <700 °C, but PAH production becomes significant at temperatures ?800 °C. Analysis of the higher-temperature reaction products by high-pressure liquid chromatography with diode-array ultraviolet-visible absorbance detection has led to the identification of over 100 PAH (ranging in size to 10 fused aromatic rings) - 47 of which have never before been reported as products of any phenol-type fuel. Quantification of the product yields shows that a much higher percentage of fed carbon is converted to PAH in the catechol-only pyrolysis experiments than in the 1,3-butadiene-only pyrolysis experiments - a result attributable to catechol’s relatively labile O-H bond and capacity for generating oxygen-containing radicals, which accelerate both fuel conversion and the pyrolysis reactions leading to 1- and 2-ring aromatics and PAH. When the two fuels are co-pyrolyzed, the percentage of the total fed carbon converting to PAH is more than two times higher than the amount calculated for the hypothetical case of the two fuels together behaving as a linear combination of the two fuels individually. This elevated production of PAH from the co-pyrolysis experiments reflects not only the reaction-accelerating role of the oxygen-containing radicals but also the efficacy, as growth agents, of the C₂ - and especially the C₄ - species abundantly present in the catechol/1,3-butadiene co-pyrolysis environment.     

Quasielastic neutrino and antineutrino scattering total cross-sections,axial-vector form-factor

Experimental results on the study of quasielastic reactionsv _μ n→μ ^? p and \(\bar v_u p \to \mu ^ + n\) in the energy range 3–30 GeV are presented in this paper. Spark chamber detector with Al filters has been exposed to the wide-band neutrino and antineutrino beams at Serpukhov. Neutrino and antineutrino data have been used to reconstruct the behaviour of axial-vector form-factorF _A (Q ²). We measured the total cross-sections as a function of energy. The parameterM _A =(1.00±0.04) GeV/c² has been determined under the assumption of the dipole parametrization and CVC hypothesis. Upper limit for the second class currents was estimated.     

Local effective polarization and absorption potentials from cross-sections for e-atom scattering

A possibility of obtaining local, effective, energy-dependent polarization and absorption potentials from experimental cross-sections for electron scattering is investigated. Potentials have been fitted with the help of the genetic algorithm on large sets of experimental data for e-He, e-Ne and e-Ar elastic scattering at impact energies 20-3000 eV. The obtained potentials reproduce the cross-sections within experimental errors.     

Electron and positron scattering from atomic potassium

The present coupled-channels-optical method (CCO) provides a comprehensive theoretical calculation of electron-potassium atom and positron-potassium atom scattering at intermediate energies. The CCO calculations for various physical observables are compared with the convergent close-coupling method (CCC) and other theoretical results, as well as experimental data where available. The CCO provides good to fair agreement with results from the convergent close coupling calculations, which are considered to be the state of the art for alkali atoms in the electron channel.     

The total virtual photoabsorption cross section,deeply virtual Compton scattering and vector-meson production

Based on the generic two-gluon-exchange dynamical mechanism for deeply inelastic scattering at low , we stress the intimate direct connection between the total virtual photoabsorption cross section, deeply virtual Compton scattering and vector-meson electroproduction. A simple expression for the cross section for deeply virtual Compton scattering is derived. Parameter-free predictions are obtained for deeply virtual Compton forward scattering and vector-meson forward production, once the parameters in the total virtual photoabsorption cross section are determined in a fit to the experimental data on deeply inelastic scattering. Our predictions are compared with the experimental data from HERA. Received: 16 February 2004, Revised: 16 July 2004, Published online: 2 September 2004 Supported by Deutsche Forschungsgemeinschaft, contract number schi 189/6-2. An erratum to this article is available at .     

Electron scattering from 70Ge and 72Ge

Cross sections have been measured for the elastic and inelastic scattering of electrons from ⁷⁰Ge and ⁷²Ge for momentum transfers from 0.65 to 1.14 fm^?1. Values for the parameters of a Fermi type ground-state charge distribution were obtained from a phase shift analysis of the elastic cross sections. The rms charge radius corresponding to these parameters is 4.07±0.02 fm for ⁷⁰Ge and 4.05±0.03 fm for ⁷²Ge. Using DWBA analysis the reduced transition probabilities for the electroexcitation of the 2₁⁺ and 3₁^? states were found to be: B(E2, ω)↑ = 19.7±1.2, 26.8±2.0 W.u.; B(E3, ω)↑ = 36±5, 37±7 W.u. for ⁷⁰Ge and ⁷²Ge respectively. The J^π = 3^? assignments for the state at 2.562 MeV in ⁷⁰Ge and 2.515 MeV in ⁷²Ge are confirmed.     

Chemisorbed hydrogen: Electron scattering,resonance levels,and vibration frequency

Several physical properties of atomic hydrogen chemisorbed on tungsten are computed on the basis of our earlier density functional calculations. The differential scattering cross-section of 50–100 eV electrons by a chemisorbed hydrogen atom is computed and compared with that of an isolated hydrogen atom. The relevance of this cross-section to LEED experiments is discussed. An electronic resonance level associated with the hydrogen atom is found at 5.6 eV below the Fermi level, in very good agreement with recent photo-emission data. The vibrational excitation energy perpendicular to the metal plane is calculated to be 200 meV, compared to the observed 140 meV.     

Effective atomic numbers of some H-, C-, N- and O-based composite materials derived from differential incoherent scattering cross-sections

In this work, we have made an effort to determine whether the effective atomic numbers of H-, C-, N- and O-based composite materials would indeed remain a constant over the energy grid of 280–1200 keV wherein incoherent scattering dominates their interaction with photons. For this purpose, the differential incoherent scattering cross-sections of Be, C, Mg, Al, Ca and Ti were measured for three scattering angles 60°, 80° and 100° at 279.1, 661.6 and 1115.5 keV using which an expression for the effective atomic number was derived. The differential incoherent scattering cross-sections of the composite materials of interest measured at these three angles in the same set-up and substituted in this expression would yield their effective atomic number at the three energies. Results obtained in this manner for bakelite, nylon, epoxy, teflon, perspex and some sugars, fatty acids as well as amino acids agreed to within 2% of some of the other available values. It was also observed that for each of these samples, Z _eff was almost a constant at the three energies which unambiguously justified the conclusions drawn by other authors earlier [Manjunathaguru and Umesh, J. Phys. B: At. Mol. Opt. Phys. 39, 3969 (2006); Manohara et al,Nucl. Instrum. Methods B266, 3906 (2008); Manohara et al Phys. Med. Biol. 53, M377 (2008)] based on total interaction cross-sections in the energy grid of interest.     

Elastic and vibrational excitation cross-sections in the Ps-H2 scattering: a perturbative approach

Summary A detailed account is reported of a perturbative calculation of the elastic and vibrational excitation cross-sections for the positronium-H₂ molecule scattering. The problem is studied in the context of the multichannel scattering theory for identical particles; the first-order exchange amplitude and the second-order direct amplitude are evaluated for energy from zero to the positronium excitation threshold. The lowest-order Padé approximant is also constructed and this suggests the occurrence of a strong enhancement in the vibrational cross-section and in the related energy loss in matter at the positronium excitation threshold. In comparison with a short preliminary account presented elsewhere, various improvements are introduced both in the physical approximations and in the numerical calculations.

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Riassunto Si dà un resoconto particolareggiato di un calcolo perturbativo della sezione d'urto elastica e di eccitazione vibrazionale per la collisione positronio su molecola d'idrogeno. Il problema è studiato nel contesto della teoria dello scattering a molti canali per sistemi di particelle identiche; sono calcolate l'ampiezza di scambio al primo ordine e l'ampiezza diretta al secondo ordine per energie da zero alla soglia di eccitazione del positronio. è anche valutata l'approssimante di Padé piú bassa e questo suggerisce la comparsa di una forte esaltazione della sezione d'urto vibrazionale e della perdita di energia nella materia attorno alla soglia di eccitazione del positronio. Rispetto ad un breve resoconto preliminare presentato in precedenza si sono apportati diversi miglioramenti sia nelle approssimazioni di carattere fisico che nelle valutazioni numeriche.

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Резюме Проводится пертурбационное вычисление поперечных сечений упругого рассеяния и вибрационного возбуждения в процессе рассеяния позитрония на молекуле H₂. Рассматриваемая проблема исследуется в связи с теорией многоканального рассеяния тождественных частиц. Вычисляются обменная амплитуда первого порядка и прямая амплитуда второго порядка в области энергий от нуля до порога возбуждения позитрония. Также определяется низший порядка Падэ приближения, предполагая наличие сильного увеличения в вибрационном поперечном сечении и в энергетических потерях в веществе на пороге возбуждения позитрония. По сравнению с существующими подходами, предлагаются различные улучшения в физических приблизениях и в численных расчетах.