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Correlation between shape resonance energies and C-C bond length in carbon-containing molecules: Elastic electron scattering and carbon K-shell excitation by photons

Description: We document the correlation of shape resonance energies resulting from (i) elastic electron scattering and (ii) carbon K-shell excitation with ic bond order (C-C bond length) for C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, C{sub 3}H{sub 8}, C{sub 4}H{sub 10}, and C{sub 6}H{sub 6}. A relationship between K-shell {sigma} resonances and bond length was experimentally pointed out previously. These correlations are qualitatively interpreted to indicate that as molecular size increases (or as bond length increases), the configuration space available for valence electrons increases, reducing energy levels rather uniformly and mowing these correlations to emerge. The similarity of shape resonances in electron scattering and photoexcitation occurs because major events in the resonances take place slightly outside the molecular field and receive little influence from the inner structure of the molecule.
Date: June 1, 1994
Creator: Kimura, Mineo
Partner: UNT Libraries Government Documents Department

Double and single ionization of He and H{sub 2} by slow protons and antiprotons

Description: Double and single ionization of He and H{sub 2} by proton (p) and antiproton ({bar p})impact in the energy region below 50 keV was studied theoretically by using the semiclassical molecular picture. As the energy decreased, the ratio of the double- to the single-ionization cross section increased for impact and decreased for p impact for both He and H{sub 2}. These trends are consistent with recent measurements for He. Ionization mechanisms differ distinctly for p impact and {bar p} impact. For p impact, the dominant mechanism for double ionization at the lower energies is sequential ladder climbing by the two electrons through various excited channels and finally into the continuum. For {bar p} impact, in contrast, the approaching negative charge distorts both the He and H{sub 2} electron clouds toward the other side of the nucleus and decreases the electron binding energies. These effects enhance electron-electron interactions, increasing double ionization. For the H{sub 2}, an effect of molecular orientation is an additional complication in determining the dynamics.
Date: December 31, 1994
Creator: Kimura, Mineo; Shimamura, Isao & Inokuti, Mitio
Partner: UNT Libraries Government Documents Department

Time-dependent aspects of electron degradation: 4, Subexcitation electrons in nitrogen and carbon dioxide

Description: We discuss here the temporal behavior of subexcitation electrons and the yields of products due to these subexcitation electrons. Our examples concern cases in which resonance scattering of electrons occurs, such as vibrational and rotational excitation in N{sub 2} and negative-ion formation in CO{sub 2}. One focus of the present work is a test of the continuous-slowing-down-approximation (CSDA) which we compare to the full solution of the time-dependent Spencer-Fano theory, which has been developed recently. 11 refs., 6 figs., 1 tab.
Date: January 1, 1988
Creator: Kimura, Mineo; Inokuti, Mitio; Kowari, Ken-ichi; Dillon, M.A. & Pagnamenta, A.
Partner: UNT Libraries Government Documents Department