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03/2007: pages 537 - 622; , ISBN: 9780470141700
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ABSTRACT: Ionization cross section, Qion, measurements by positron impact on He and Ar atoms have been performed using a time-of-flight method, and analyzed with interest in their threshold behavior. The experimental data of this work and our previous ionization cross section data are compared with those of Knudsen et al. and other data. The exponent (n) of the excess energy, E−Eion, is 1.0–1.3, which differs from the theoretical value n = 2.651. The threshold behavior of excitation cross sections, Qex, by positron impact on the same atoms, is also discussed.
Applied Surface Science 85:59-63. · 2.10 Impact Factor
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ABSTRACT: Total cross sections for 0.7–400 eV positrons colliding with CCl4 have been first measured by a time-of-flight (TOF) experiment. The measured data were corrected for the effect of forward scattering. The electron scattering measurements have also been performed for comparison with the positron scattering data. The electron results were compared with other experimental data and theoretical results.
Applied Surface Science 85:64-68. · 2.10 Impact Factor
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ABSTRACT: Total cross-sections for electron (e−) and positron (e+) scattering from CHF3 have been measured from 0.7 to 600 eV and compared with the theoretical elastic cross-section. For e− scattering, the cross-sections are found to be larger by 30% than the data compiled by Christophorou et al. [L.G. Christophorou, J.K. Olthoff, M.V.V.S. Rao, J. Phys. Chem. Ref. Data 26 (1997) 1] in the entire energy range measured, but their energy dependence is in good agreement. For e+ scattering, the cross-sections are smaller by at least a factor of two than those for electron scattering below 20–30 eV, but quickly approach those of electron impact beyond 100 eV. A comparative study with CH4 and CF4 reported in our previous papers provides detailed information on the dynamics.
Chemical Physics Letters 288(1):124-130. · 2.34 Impact Factor
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ABSTRACT: Total cross sections for electron (e-) and positron (e+) scattering from C3H8 and C3F8 have been measured from 0.8 to 600 eV and 0.7 to 600 eV, respectively. We have also investigated differential elastic cross sections by electron impact from 2.0 to 200 eV, and compared them with the present theoretical results. For e- scattering from C3H8, the cross sections are found to be larger by a factor of 2 than those of e+ scattering below 20–30 eV. They show a large peak at 8 eV due to a shape resonance and a shoulderlike structure in the region of 20–40 eV. For e- scattering from C3F8, the cross sections are again larger by at least a factor of 2 than those of e+ scattering below 50 eV, and they have two peaks at 4 and 8 eV, followed by a broad peak in the region of 20–40 eV. Some small structures overlie the broad hump. Both e- and e+ impact cross sections for C3H8 and C3F8 quickly approach each other beyond 200 eV. From the differential cross section study, we have been able to provide more detailed information on shape resonances, and also we have carried out some analysis of resonances in vibrational excitation results. In general, the total and integrated elastic cross sections are in good qualitative and quantitative agreement.
Phys. Rev. A. 59(3).
