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Title: Electron-impact electronic excitation of molecular nitrogen using the Schwinger multichannel variational method

Abstract

The Schwinger multichannel method is applied to study the low-energy electron-impact excitation of molecular nitrogen. The scattering amplitudes are obtained within the minimal orbital basis for single configuration interactions (MOBSCI) level of approximation, for impact energies from near threshold up to 30 eV. Through the use of the MOBSCI strategy we have performed a close-coupling calculation for up to nine states, including the ground state and all singlet and triplet states resulting from the {pi}{sub u}{yields}{pi}{sub g} transitions. Integral and differential cross sections for the X {sup 1}{sigma}{sub g}{sup +}{yields}A {sup 3}{sigma}{sub u}{sup +}, W {sup 3}{delta}{sub u}, B{sup '} {sup 3}{sigma}{sub u}{sup -}, a{sup '} {sup 1}{sigma}{sub u}{sup -}, and w {sup 1}{delta}{sub u} electronic transitions are presented and compared with available experimental data and also with other theoretical results.

Authors:
;  [1]
  1. Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, Caixa Postal 6165, 13083-970 Campinas, Sao Paulo (Brazil)
Publication Date:
OSTI Identifier:
20982119
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevA.75.022705; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; APPROXIMATIONS; CONFIGURATION INTERACTION; COUPLING; DIFFERENTIAL CROSS SECTIONS; ELECTRON-MOLECULE COLLISIONS; ELECTRONS; EV RANGE; EXCITATION; GROUND STATES; NITROGEN; SCATTERING AMPLITUDES; TRIPLETS; VARIATIONAL METHODS

Citation Formats

Da Costa, Romarly F., and Lima, Marco A. P. Electron-impact electronic excitation of molecular nitrogen using the Schwinger multichannel variational method. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.022705.
Da Costa, Romarly F., & Lima, Marco A. P. Electron-impact electronic excitation of molecular nitrogen using the Schwinger multichannel variational method. United States. doi:10.1103/PHYSREVA.75.022705.
Da Costa, Romarly F., and Lima, Marco A. P. Thu . "Electron-impact electronic excitation of molecular nitrogen using the Schwinger multichannel variational method". United States. doi:10.1103/PHYSREVA.75.022705.
@article{osti_20982119,
title = {Electron-impact electronic excitation of molecular nitrogen using the Schwinger multichannel variational method},
author = {Da Costa, Romarly F. and Lima, Marco A. P.},
abstractNote = {The Schwinger multichannel method is applied to study the low-energy electron-impact excitation of molecular nitrogen. The scattering amplitudes are obtained within the minimal orbital basis for single configuration interactions (MOBSCI) level of approximation, for impact energies from near threshold up to 30 eV. Through the use of the MOBSCI strategy we have performed a close-coupling calculation for up to nine states, including the ground state and all singlet and triplet states resulting from the {pi}{sub u}{yields}{pi}{sub g} transitions. Integral and differential cross sections for the X {sup 1}{sigma}{sub g}{sup +}{yields}A {sup 3}{sigma}{sub u}{sup +}, W {sup 3}{delta}{sub u}, B{sup '} {sup 3}{sigma}{sub u}{sup -}, a{sup '} {sup 1}{sigma}{sub u}{sup -}, and w {sup 1}{delta}{sub u} electronic transitions are presented and compared with available experimental data and also with other theoretical results.},
doi = {10.1103/PHYSREVA.75.022705},
journal = {Physical Review. A},
number = 2,
volume = 75,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • As a first application of the Schwinger multichannel theory, we have calculated integral and differential cross sections for electron-impact excitation of the transition X /sup 1/..sigma../sub g//sup +/..-->..b /sup 3/..sigma../sub u//sup +/ in H/sub 2/ for scattering energies from 13 to 30 eV at the two-state level. We find good agreement between our integral cross sections and the results obtained previously in a two-state close-coupling study. Our method does not rely on single-center expansions to calculate the body-frame scattering amplitude and is designed to be applicable to molecules of arbitrary geometry.
  • The complex Kohn variational method is employed in four-state close-coupling calculations to generate integral and differential cross sections for low-energy electron-impact excitation of the {sup 1}{Sigma}{sub g}{sup +}{r arrow}(b {sup 3}{Sigma}{sub u}{sup +}, {sup 3}{Sigma}{sub g}{sup +}, and {ital c} {sup 3}{Pi}{sub {ital u}}) transitions in H{sub 2}. The integral cross sections for excitation of the {sup 3}{Sigma}{sub g}{sup +} and {ital c} {sup 3}{Pi}{sub {ital u}} states from the ground state are found to be significantly different from earlier two-state calculations. The {ital a} {sup 3}{Sigma}{sub {ital g}}{sup +} cross sections are also larger than the most recent experimentalmore » results. This discrepancy is traced to the behavior of the differential cross sections at scattering angles near 0{degree} and 180{degree}, where measurements have not been carried out. The differential cross sections we find for H{sub 2} are strikingly similar to cross sections for analogous transitions in He. Previous theoretical studies of these transitions in He have also shown the two-state approximation to be inadequate.« less
  • In this paper we report cross sections for electron-impact excitation of the X /sup 1/..sigma../sub g//sup +/..-->..B /sup 1/..sigma../sub u//sup +/ transition in H/sub 2/ for collision energies of 15, 20, and 30 eV. For this dipole-allowed transition with its associated long-range potential, the contributions of the more strongly scattered low-angular-momentum partial waves to the cross section were obtained from a two-state Schwinger multichannel calculation, and a modified Born-closure scheme was used to include the contributions from the remaining weakly scattered partial waves. Agreement between the calculated differential cross sections and available experimental data is encouraging.
  • We report integral and differential cross sections for the electron-impact excitation of the {ital b} {sup 3}{Sigma}{sup +} state of CO using the Schwinger multichannel formulation. The calculations were carried out using a two-state approximation, with the incident electron energies in the range from 10.66 to 20 eV. We find four peaks in the inelastic cross section, centered at approximately 10.87, 11.6, 13.4, and 16.2 eV. The origins of the peak structures are discussed in terms of a partial-wave analysis, and comparison is made with experiment and theory where appropriate. We attribute the two sharp, low-energy (10.87 and 11.6 eV)more » peaks to the decay of {sup 2}{Sigma}{sup +} core-excited Rydberg resonance states of CO{sup {minus}}. The two higher-energy peaks are broad and less well defined. The 13.4-eV peak is not clearly identifiable as a resonance, whereas the 16.2-eV peak in the inelastic cross section occurs as a result of a {sup 2}{Sigma}{sup +} shape resonance in the elastic channel of the {ital b}{sup 3}{Sigma}{sup +} state. The magnitudes of the cross sections indicate that the {sup 2}{Sigma}{sup +} symmetry is dominant for all four peaks. In all the resonances, we find more than one partial wave contributing at energies slightly shifted with respect to each other. The present calculation represents the first {ital ab} {ital initio} study of core-excited Rydberg resonances in electron-molecule scattering.« less
  • The mutlichannel Schwinger variational formalism in the momentum space has been used to investigate elastic scattering and the ground-state positronium formation process in the positron-hydrogen collisions in the Ore gap region, 6.8--10.2 eV. The [ital s]-wave results obtained by employing a correlated discrete basis set are found to be in agreement with existing accurate Kohn variational results of Humberston [Can. J. Phys. 60, 591 (1982)].