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  • 1
    Electronic Resource
    Electronic Resource
    Evidence for a partial breakdown of the molecular orbital picture in the ionization spectra of large saturated hydrocarbons (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 7583-7596 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The x-ray photoionization spectra of large saturated hydrocarbons have been investigated by means of one-particle Green's function calculations. These spectra saturate overall rather quickly to their asymptotic form with increasing system size. The results obtained indicate a severe breakdown of the molecular orbital picture of ionization above a binding energy threshold of about 23 eV, for n-alkane chains ranging from n-propane to n-nonane, or cycloalkane compounds such as cyclobutane, cyclopentane, and cyclohexane. In spite of the fast multiplication of satellite solutions, shake-up lines remain confined above that threshold, as a result of the delocalization properties of one-electron canonical states. The ring closure is shown to emphasize the dispersion of photoionization intensity into satellites. Conformational changes, on the other hand, have only marginal effects on the convoluted correlation bands. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472585
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  • 2
    Electronic Resource
    Electronic Resource
    On the size-dependence of the static self-energy in propagator calculations (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 3578-3588 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Various approximations are used currently to evaluate the static part Σ(∞) of the self-energy or optical potential in molecular Green's function calculations. Since its expansion is ruled out by the linked-cluster theorem, one generally assumes a size-intensive behavior of Σ(∞) in the thermodynamic limit of an infinite system. A detailed analysis of this size-dependence property is conducted using the formulation of crystalline orbitals (CO) for stereoregular polymers. In spite of the linked-cluster theorem, this study provides evidence for a logarithmic divergence with respect to the size of a chain for some forms of Σ(∞), computed with common approximation schemes. This is the direct outcome of the long-range character of the Coulombic interaction and can be related to a violation in the number of particles within the system. A proper size-intensive behavior implies an exact cancellation of the logarithmically divergent behavior of antigraphs. The conclusions drawn from CO analysis are confirmed by numerical tests on model oligomer systems. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470241
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  • 3
    Electronic Resource
    Electronic Resource
    The electronic structure of molecules by a many-body approach (1977)
    Springer
    Theoretical chemistry accounts 44 (1977), S. 85-93 
    Details
    ISSN: 1432-2234
    Keywords: C3H6 ring molecule, ionization potential of ∼ ; C2H4O ring molecule, ionization potential of ∼ ; C2H5N ring molecule, ionization potential of ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The vertical valence ionization potentials of cyclopropane, ethylene oxide and ethylene imine are calculated by a many-body Green's function method. For C3H6 the ordering of the ionization potentials is 2e′(σ), 1e″(π), 2a′1(σ), 1a″2(π), 1e′(σ). The assignment of the 2a′1 and the 1a″2 ionization potentials which has been controversial is thus clarified. The ordering is in agreement with the result obtained via Koopmans' theorem. For ethylene oxide and ethylene imine Koopmans' theorem fails in predicting the correct order of ionic states. For C2H4O the ordering of the ionization potentials is 2b 1(π), 4a 1, 1a 2(π), 2b 2,3a 1, 1b 1(π), 1b 2, 2a 1 and for C2H5N 6a′, 5a′, 3a″, 2a″, 4a′, 3a′, 1a″, 2a′. The agreement of the computed ionization potentials with the experimental values is very satisfactory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548031
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  • 4
    Electronic Resource
    Electronic Resource
    Correlation effects in the valence x-ray photoionization spectra of ethylene, butadiene, and hexatriene (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 465-481 
    Details
    ISSN: 0020-7608
    Keywords: excited states ; shake-up ; relaxation ; electronic correlation ; Green's function ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The x-ray photoemission spectra of the ethylene, butadiene, and hexatriene compounds were investigated using one-particle Green's function calculations which are exact up to third order in correlation. This study points to the importance of initial-state correlation and cross-section effects for a consistent reproduction of satellite bands recorded under x-ray photoionization. By extrapolating the results obtained to larger unsaturated hydrocarbons, it is clear that the signal recorded in the inner-valence region of polyacetylene must be exclusively assigned to many-body structures. This study also provides evidence for a partial contamination of the outer-valence band by shake-up lines. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 465-481, 1997
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Stabile freie dianionische Silicium-Kohlenstoff-Cluster (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 109 (1997), S. 1949-1951 
    Details
    ISSN: 0044-8249
    Keywords: Ab-initio-Rechnungen ; Silicium ; Kohlenstoff ; Cluster ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19971091719
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  • 6
    Electronic Resource
    Electronic Resource
    Stable Free Dianionic Silico—Carbon Clusters (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 36 (1997), S. 1889-1891 
    Details
    ISSN: 0570-0833
    Keywords: ab initio calculation ; carbon ; clusters ; silicon ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199718891
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