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Title: Angular distribution of low-energy electron emission in collisions of 6-MeV/u bare carbon ions with molecular hydrogen: Two-center mechanism and interference effect

Abstract

We report the energy and angular distribution of electron double differential cross sections (DDCS) in collision of 6-MeV/u C{sup 6+} ions with molecular hydrogen. We explain the observed distributions in terms of the two-center effect and the Young-type interference effect. The secondary electrons having energies between 1 and 1000 eV are detected at about 10 different emission angles between 30 degree sign and 150 degree sign . The measured data are compared with the state-of-the-art continuum distorted wave-eikonal initial state and the first Born model calculations which use molecular wave function. The single differential cross sections are derived and compared with the theoretical predictions. The oscillations due to the interference effect are derived in the DDCS ratios using theoretical cross sections for the atomic H target. The effect of the atomic parameters on the observed oscillations is discussed. An evidence of interference effect has also been shown in the single differential cross section. The electron energy dependence of the forward-backward asymmetry parameter shows a monotonically increasing behavior for an atomic target, such as He, which could be explained in terms of the two-center effect only. In contrast, for the molecular H{sub 2} the asymmetry parameter reveals an oscillatory behavior duemore » to the Young-type interference effect superimposed with the two-center effect. The asymmetry parameter technique provides a self-normalized method to reveal the interference oscillation which does not require either a theoretical model or complementary measurements on the atomic H target.« less

Authors:
; ; ; ; ; ;  [1];  [2]
  1. Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005 (India)
  2. (Argentina)
Publication Date:
OSTI Identifier:
20982530
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.75.052712; (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; ANGULAR DISTRIBUTION; ASYMMETRY; CARBON IONS; DIFFERENTIAL CROSS SECTIONS; DISTORTED WAVE THEORY; EIKONAL APPROXIMATION; ELECTRON EMISSION; ENERGY DEPENDENCE; ENERGY SPECTRA; EV RANGE; HYDROGEN; HYDROGEN 1 TARGET; INTERFERENCE; ION-MOLECULE COLLISIONS; IONIZATION; MEV RANGE 01-10; MOLECULES; OSCILLATIONS; WAVE FUNCTIONS

Citation Formats

Misra, Deepankar, Kelkar, A., Kadhane, U., Kumar, Ajay, Singh, Y. P., Tribedi, Lokesh C., Fainstein, P. D., and Centro Atomico Bariloche, Comision Nacional de Energia Atomica, Avenida E. Bustillo 9500, 8400 Bariloche. Angular distribution of low-energy electron emission in collisions of 6-MeV/u bare carbon ions with molecular hydrogen: Two-center mechanism and interference effect. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.052712.
Misra, Deepankar, Kelkar, A., Kadhane, U., Kumar, Ajay, Singh, Y. P., Tribedi, Lokesh C., Fainstein, P. D., & Centro Atomico Bariloche, Comision Nacional de Energia Atomica, Avenida E. Bustillo 9500, 8400 Bariloche. Angular distribution of low-energy electron emission in collisions of 6-MeV/u bare carbon ions with molecular hydrogen: Two-center mechanism and interference effect. United States. doi:10.1103/PHYSREVA.75.052712.
Misra, Deepankar, Kelkar, A., Kadhane, U., Kumar, Ajay, Singh, Y. P., Tribedi, Lokesh C., Fainstein, P. D., and Centro Atomico Bariloche, Comision Nacional de Energia Atomica, Avenida E. Bustillo 9500, 8400 Bariloche. Tue . "Angular distribution of low-energy electron emission in collisions of 6-MeV/u bare carbon ions with molecular hydrogen: Two-center mechanism and interference effect". United States. doi:10.1103/PHYSREVA.75.052712.
@article{osti_20982530,
title = {Angular distribution of low-energy electron emission in collisions of 6-MeV/u bare carbon ions with molecular hydrogen: Two-center mechanism and interference effect},
author = {Misra, Deepankar and Kelkar, A. and Kadhane, U. and Kumar, Ajay and Singh, Y. P. and Tribedi, Lokesh C. and Fainstein, P. D. and Centro Atomico Bariloche, Comision Nacional de Energia Atomica, Avenida E. Bustillo 9500, 8400 Bariloche},
abstractNote = {We report the energy and angular distribution of electron double differential cross sections (DDCS) in collision of 6-MeV/u C{sup 6+} ions with molecular hydrogen. We explain the observed distributions in terms of the two-center effect and the Young-type interference effect. The secondary electrons having energies between 1 and 1000 eV are detected at about 10 different emission angles between 30 degree sign and 150 degree sign . The measured data are compared with the state-of-the-art continuum distorted wave-eikonal initial state and the first Born model calculations which use molecular wave function. The single differential cross sections are derived and compared with the theoretical predictions. The oscillations due to the interference effect are derived in the DDCS ratios using theoretical cross sections for the atomic H target. The effect of the atomic parameters on the observed oscillations is discussed. An evidence of interference effect has also been shown in the single differential cross section. The electron energy dependence of the forward-backward asymmetry parameter shows a monotonically increasing behavior for an atomic target, such as He, which could be explained in terms of the two-center effect only. In contrast, for the molecular H{sub 2} the asymmetry parameter reveals an oscillatory behavior due to the Young-type interference effect superimposed with the two-center effect. The asymmetry parameter technique provides a self-normalized method to reveal the interference oscillation which does not require either a theoretical model or complementary measurements on the atomic H target.},
doi = {10.1103/PHYSREVA.75.052712},
journal = {Physical Review. A},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • We use the forward-backward angular asymmetry in the electron emission cross sections in fast ion impact ionization of H{sub 2} as a probe of the inversion symmetric coherence in homonuclear diatomic molecules. The electron energy dependence of the asymmetry parameter for H{sub 2} exhibits oscillatory structure due to Young-type interference in contrast to atomic targets such as He. The asymmetry parameter technique provides a self-normalized method to reveal the interference oscillation independent of theoretical models and complementary measurements on atomic H target.
  • We have measured the double differential cross sections (DDCS) ({ital d}{sup 2}{sigma}/{ital d}{var_epsilon}{sub {ital ed}}{Omega}{sub {ital e}}) of low-energy electron emission in the ionization of H{sub 2} bombarded by bare carbon ions of energy 30 MeV. The energy and angular distributions of the electron DDCS have been obtained for 12 different emission angles and for electron energies varying between 0.1 and 300 eV. We have also deduced the single differential and total ionization cross section from the measured DDCS. The data have been compared with the predictions of first Born approximations and the CDW-EIS (continuum distorted wave{endash}eikonal initial state) model.more » The CDW-EIS model provides an excellent agreement with the data. {copyright} {ital 1996 The American Physical Society.}« less
  • The angular distribution, as well as the energy distribution of [delta] electrons produced in collisions of 1.0-MeV/u F[sup [ital q]+] ([ital q]=4,6,8,9) ions with molecular hydrogen, have been studied for laboratory observation angles ([theta][sub [ital L]]) from 0[degree] to 70[degree] with respect to the beam direction. The measurements are in fair agreement with the impulse approximation calculations which use the quantal elastic electron-ion differential scattering cross sections folded with the Compton profile of the target electrons. We observe that the energy of the centroid of the binary-encounter-electron (BEE) peak is projectile charge state, [ital q], and laboratory angle, [theta][sub [italmore » L]], dependent. Moreover, at 0[degree], an enhancement of the ratio of the observed double differential cross section for nonbare projectiles to that for the bare ion projectiles, [sigma]([ital q]+)/[sigma](9+), is observed, contrary to the [ital q][sup 2] scaling predicted by a first Born calculation for ionization. This ratio [sigma]([ital q]+)/[sigma](9+) decreases nonotonically with increasing [theta][sub [ital L]], and becomes smaller than one for [theta][sub [ital L]][ge]30[degree].« less
  • Electron-capture processes in collisions of C{sup 5+} ions with H atoms are investigated theoretically by using quantum-mechanical and semiclassical molecular-orbital methods in the collision-energy range from meV/amu to keV/amu. Atomic-type electron-translation factors are appropriately incorporated to ensure correct scattering boundary conditions. Total capture cross sections have a broad minimum at 0.4 keV/amu that is caused by the change of major contributors. The dominant capture channels in the triplet manifold are C{sup 4+}(1{ital s}4{ital s}) below 0.1 keV/amu and C{sup 4+}(1{ital s}4{ital p}), C{sup 4+}(1{ital s}4{ital d}), and C{sup 4+}(1{ital s}3{ital p}) above that energy. In the singlet manifold, below 0.5more » keV/amu, the dominant channel is C{sup 4+}(1{ital s}4{ital s}), as in the triplet manifold. However, above that energy the C{sup 4+}(1{ital s}4{ital f}), C{sup 4+}(1{ital s}4{ital d}), C{sup 4+}(1{ital s}3{ital p}), and C{sup 4+}(1{ital s}3{ital d}) channels become important. The present results for the total capture cross section is in excellent accord with the measurements by Phaneuf {ital et} {ital al}. (Phys. Rev. A 26, 1892 (1982)) and Crandall, Phaneuf, and Meyer (Phys. Rev. A 19, 504 (1979)) over the entire energy region studied. The effect of core electrons on the capture process is examined by using data from the present (C{sup 5+}+H) system and the previously studied (N{sup 5+}+H) and (B{sup 5+}+H) systems, and some remarks on the role of core electrons are made on the basis of an argument concerning the overlap of electronic charge distribution.« less