Grand Total Cross Sections Research Articles

Electron collisions with CO: Elastic and vibrational excitation cross sections

Absolute differential elastic and vibrational excitation cross sections up to $v=11$ were measured for CO in scattering angle ranges extending to ${180}^{\ifmmode^\circ\else\textdegree\fi{}}$ at energies between 0.2 and 5 eV (and an elastic measurement at 10 eV). The lowest angles were ${0}^{\ifmmode^\circ\else\textdegree\fi{}}$ for inelastic scattering and between ${5}^{\ifmmode^\circ\else\textdegree\fi{}}$ and ${20}^{\ifmmode^\circ\else\textdegree\fi{}}$ for elastic scattering, depending on energy. Integral cross sections were derived by integrating under the angular distributions and compared with previous beam and swarm measurements. The sum of the integral cross sections agrees very well with the available transmission measurements of the grand total cross section, thus validating the present measurements. The present elastic differential and integral cross sections are in excellent agreement with the best available measurement [Gibson et al., J. Phys. B 29, 3197 (1996)], but the $v=1$ inelastic cross section is about $25%$ higher. This could have consequences for simulations of cometary and planetary atmospheres.

Computation of total electron scattering cross sections for molecules of astrophysical relevance

In this paper we report calculations of various total cross sections namely total elastic (Qel), total ionization (Qion), total (complete) cross sections (QT) and grand total cross sections (QTOT) for the impact of electrons on methyl compounds namely, methanol, methylamine and total ionization cross sections on reactive diatomic radical SO and SO2 molecule at energies from circa threshold to 2000 eV. We have employed the ‘Spherical Complex Optical Potential’ (SCOP) formalism to evaluate Qel, Qinel, QT and QTOT and used our semi-empirical, ‘Complex Spherical Potential — ionization contribution’ (CSP-ic) method to derive Qion. These results are compared with available experimental and other theoretical data and overall good agreement is observed

Low-energy electron scattering ofNO:Ab initioanalysis of theΣ−3,Δ1, andΣ+1shape resonances in the local complex potential model

We present an ab initio study of elastic scattering and vibrational excitation of $\mathrm{NO}$ by low-energy $(0--2.0\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ electron impact. The low-energy scattering cross sections are dominated by shape resonance contributions associated with the $^{3}\ensuremath{\Sigma}^{\ensuremath{-}}$, $^{1}\ensuremath{\Delta}$, and $^{1}\ensuremath{\Sigma}^{+}$ states of ${\mathrm{NO}}^{\ensuremath{-}}$. Resonance parameters for the three anion states were extracted from an analysis of fixed-nuclei variational (complex Kohn) calculations that employed elaborate trial wave functions. Independent estimates of the resonance parameters were obtained by analytically continuing the results of large-scale coupled-cluster calculations into the plane of complex momentum. The local complex potential model was used to calculate vibrational excitation cross sections, as well as the resonant portion of the vibrationally elastic cross sections. These results were combined with background contributions from the fixed-nuclei calculations to compute elastic and grand total cross sections. Our results capture the essential features of recent measurements of the cross sections, but suggest the need at lower energies for a more sophisticated, nonlocal treatment of nuclear dynamics.

Relationship between electron-scattering grand total and ionization total cross sections

Regression formula which relates grand total cross section and ionization total cross section for electron scattering from simple hydrocarbons and from perfluorinated molecules has been proposed. This formula was then used to evaluate the ionization total cross sections for WF 6 and for structured isomers of C 3H 4 and C 4H 6, at intermediate electron-impact energies. For WF 6 the estimated ionization cross section is compared with available experimental and theoretical data. In addition, for C 3H 4 and C 4H 6 ionization total cross sections were calculated with the binary-encounter Bethe (BEB) model to compare with the values predicted from the regression formula. Grand total cross section for electron scattering from UF 6 molecules was also estimated over energy range from 20 to 400 eV.

Electronscattering from disilane (Si2H6) molecules. Absolutetotal cross section measurements from 1 to 370 eV

Absolute grand total cross sections (TCSs) for electron-disilane(Si2H6) scattering have been measured over the energyrange from 1 to 370 eV in a linear transmission experiment.The low-energy TCS is dominated by a broadresonant-like enhancement. In the region of the maximum thepresent grand TCS values appeared to bedistinctly lower than previously reported integral elasticcross section data. A comparison of total electron scatteringcross sections for the two simplest silicon hydrides and relevanthydrocarbons is given.

Excitation of vibrational quanta in water by electron impact

A comprehensive study of absolute differential cross sections (DCSs) forelectron impact excitation of the bending (010) and unresolved stretching(100 + 001) vibrational quanta of water (H2O) is reported. Eightincident electron energies (E0) in the range 6-20 eV wereinvestigated, and the scattered electron angular range was10°-135°. Integral cross sections (ICSs) were derived fromthe corresponding vibrational DCSs using a molecular phase shift analysistechnique. The self-consistency of these vibrational ICSs was consideredby summing them, at each E0, with available elastic and ionization ICSto provide estimates for the H2O grand total cross section (GTS),which could then be checked against the independent GTSs of Szmytkowski(1987 Chem. Phys. Lett. 136 363) and Sueoka et al (1986 J. Phys. B: At. Mol. Phys. 19 L373). Good agreement was typicallyfound.

Electron-impact excitation of Rydberg and valence electronic states of nitric oxide: II. Integral cross sections

Integral cross sections (ICSs) for the excitation of 18 excited electronic states, and four composite excited electronic states, in nitric oxide (NO) have been determined for incident electron energies of 15, 20, 30, 40 and 50 eV. These ICSs were derived by extrapolating the respective measured differential cross sections (M J Brunger et al 2000 J. Phys. B: At. Mol. Opt. Phys. 33 783) to 0° and 180° and by performing the appropriate integration. Comparison of the present ICSs with the results of those determined in earlier optical emission measurements, and from theoretical calculations is made. At each incident energy considered, the current ICSs are also summed along with the corresponding elastic and rovibrational excitation ICSs from B Mojarrabi et al (1995 J. Phys. B: At. Mol. Opt. Phys. 28 487) and the ionization cross sections from Rapp and Englander-Golden (1965 J. Chem. Phys. 43 1464), to derive an estimate of the grand total cross sections (GTSs) for e-+ NO scattering. The GTSs derived in this manner are compared with the results from independent linear transmission experiments and are found to be entirely consistent with them. The present excited electronic state ICS, and those for elastic and rovibrational excitation from Mojarrabi et al, appear to represent the first set of self-consistent cross sections for electron impact scattering from NO.

Elastic electron scattering from helium: absolute experimental cross sections, theory and derived interaction potentials

The authors report new differential cross section measurements (E0=1.5-50 eV) and coupled channel optical model calculations for elastic scattering of electrons from helium. The experimental results, from a crossed electron-atomic beam apparatus are analysed via a complex phaseshift technique with the derived phaseshifts, and their associated errors, then being used to derive total elastic, total reaction, total momentum transfer and grand total cross sections, and their respective errors, in a mathematically rigorous manner. Further, the authors applied fixed-energy inverse scattering techniques to the present data in order to deduce the interaction potential between the colliding particles.