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  • 1985-1989  (5)
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Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Differential nonreactive scattering of He*(2 1S, 2 3S) by D2 and H2: Anisotropic optical potentials and comparison with ab initio theory (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 2630-2643 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Angular distributions of He*(2 1S, 2 3S) scattered by D2 and H2 measured in crossed supersonic molecular beams at collision energies in the range 1.0–2.4 kcal/mol are analyzed to yield anisotropic optical potentials that simultaneously reproduce these data along with quenching rates and ionization cross sections. Comparison with ab initio calculations of the potentials by Cohen and Lane and Hickman, Isaacson, and Miller shows very good agreement. The results are combined with one-electron model potential calculations to probe the nuclear and electronic dynamics involved in these collisions. Quenching or Penning ionization is found to occur mainly through broadside attack of He* on H2, despite the fact that the occupied σg orbital on H2 has greater spatial extent along the bond axis than perpendicular to it. An implication is that Penning ionization electron spectroscopy (PIES) experiments on larger molecules cannot be interpreted simply on the basis of van der Waals radii and spatial extent of various molecular orbitals; the nature of the excited-state potential surface may play a dominant role in determining these spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448313
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Collision energy dependence of product branching in Penning ionization: He*(2 1S, 2 3S) + H2, D2, and HD (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1564-1576 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Relative ionization cross sections for the title systems with articulation of all product ion channels have been measured in the collision energy range 1.5–4.0 kcal/mol using crossed supersonic molecular beams; the H2 results have been extended down to 0.5 kcal/mol by the use of a 10% H2/Ar seeded beam. The data are interpreted with a microscopic two-step model that assumes ionization near the turning point in the excited state, a centrifugal barrier criterion for ionic complex formation, and statistical partitioning of flux among the possible ionic products, i.e., phase-space theory. A full statistical calculation underestimates the amount of rearrangement ionization He*+H2→HeH++H+e− by a factor of 2, but one which excludes antiparallel coupling of orbital and rotational angular momenta in the H+2 channel is in better accord with the data. A substantial isotope effect favoring HeD+ over HeH+ in the HD reactions by a factor of 1.9±0.2 is well represented by the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456049
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Close-coupling optical model analysis: A refined optical potential surface for He*(2 1S)+H2 (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 240-245 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A complex-arithmetic version of Johnson's log–derivative integration method has enabled a straightforward extension of the close-coupling approximation to complex-potential surfaces. The complex-potential close-coupling (CPCC) method is applied to the determination from our earlier scattering measurements of an improved anisotropic optical potential for the He*(2 1S)+H2 Penning ionization system, with the aid of a new, nonpiecewise potential surface function based on the improved Tang–Toennies model. The potential is compared to earlier ab initio results, and the CPCC method is used to assess the shortcomings of the complex-infinite-order-sudden (CIOS) approximation. Variation of differential and ionization cross sections with the initial rotational state of H2 predicted by CPCC may be experimentally observable, and may also provide an explanation for the observed H2/D2 isotope effect in quenching rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455511
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Common Denominators of Promoter Control in Pseudomonas and Other Bacteria (1989)
    [s.l.] : Nature Publishing Company
    Nature biotechnology 7 (1989), S. 1249-1254 
    Details
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The analysis of gene regulation in bacteria is entering a new phase. Global regulatory networks, signal processing, responses of complexly regulated sets of genes, and interactions between regulatory systems are becoming a focus of intensive research efforts. Our understanding of how bacteria ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nbt1289-1249
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    Paper (German National Licenses)
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  • 5
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    The Pushkin Celebrations of 1880: The Conflict of Ideals and Ideologies (1988)
    London, etc. : Periodicals Archive Online (PAO)
    Slavonic and East European review. 66:4 (1988:Oct.) 505 
    Details
    ISSN: 0037-6795
    Topics: History , Slavonic Studies
    Notes: Literature
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:0072-1988-066-04-000001
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    Paper (German National Licenses)
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