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  • 1990-1994  (7)
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  • 1990-1994  (7)
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Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Formation of the superhalogen ion SF−7 via electron attachment to SF6 clusters (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 9241-9242 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electron attachment to SF6 and SF6 clusters has been investigated in a molecular beam/electron impact ion source/mass spectrometer system. In accordance with recent theoretical predictions we were able to produce the superhalogen ion SF7− by electron attachment to SF6 clusters. SF7− has not been previously observed; its relative attachment cross section curve shows features more similar to that of F2− from SF6 than that of F− from SF6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462236
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Metastable fragmentation of (C4H10)nC4H+7 cluster ions induced by delayed isomerization reactions of C4H+7 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5213-5219 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The metastable fragmentation of the cluster ions (C4H10)nC4H+q (q=7 to 10) produced by the electron impact ionization of a neutral n-butane cluster beam has been studied with a double focusing sector field mass spectrometer. For q〉7, the usual statistical single-monomer evaporation is the only observable metastable fragmentation channel. Surprisingly, the (C4H10)nC4H+7 cluster ions were found to exhibit a more complex metastable decay pattern, involving not only the single-monomer evaporation, but also two additional fragmentation channels leading to evaporation of 2 to 4 and 4 to 7 (C4H10) monomers, respectively. After studying the dependence of the parent and the fragment ion currents on the electron energy, we concluded that the C4H+7 ionic chromophore of the (C4H10)nC4H+7 cluster ion is produced after internal H− transfer between n-C4H10 and some primary fragment ion (e.g., C2H+5, C2H+3, C3H+3, CH+3, C3H+4 ) of n-butane within the cluster. A mechanism based on the energy storage in metastable isomers of the C4H+7 chromophore ion is suggested to explain the unusual metastable fragmentation pattern of (C4H10)nC4H+7 cluster ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462729
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Autoscavenging of electrons in mixed van der Waals clusters: a new approach to the spectroscopy of cluster anions (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 1528-1530 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100183a006
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Production and properties of CO2 cluster anions (1992)
    Springer
    The European physical journal 24 (1992), S. 289-296 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 35.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stoichiometric and non-stoichiometric negatively charged CO2 cluster ions have been produced in a crossed neutral cluster/electron beam ion source. The abundance and stability of these ions have been studied with a double focussing sector field mass spectrometer. The observed abundance anomalies (“magic numbers”) in the mass spectra of (CO2) n − and (CO2) n O− ions correlate with corresponding small and large metastable fractions of these ions (for loss of one CO2 unit). Variation of the measured metastable fractions as a function ofn are related to corresponding changes in the monomer binding energies. In addition, we have observed for the first time (CO2) n O 2 − ions (i.e. at electron energies above 8 eV with an energy resonance at about 14 eV) and we discuss possible production mechanisms for these ions. Relative electron attachment cross sections have been determined in the energy regime O〈E≦20 eV for (CO2) n − , (CO2) n O− and (CO2) n O 2 − withn=1 to 20. The shape of the cross section function for (CO2) n O− is strongly dependent on the cluster sizen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01425751
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Absolute partial and total electron impact ionization cross sections for C3H8 from threshold up to 950 eV (1993)
    Springer
    The European physical journal 25 (1993), S. 217-226 
    Details
    ISSN: 1434-6079
    Keywords: 34.80.Gs ; 35.20.Wg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electron impact ionization of propane (C3H8) was studied using the ion beam deflection technique and a double focussing mass spectrometer in conjunction with a recently developed correction procedure that accounts for discrimination due to the initial kinetic energy of fragment ions. The relative corrected partial ionization cross sections for the production of C3H 8 + , C3H 7 + , C3H 6 + , C3H 5 + , C3H 4 + , C3H 3 + , C3H 2 + , C3H+, C 3 + ; C2H 5 + , C2H 4 + , C2H 3 + , C2H 2 + , C2H+, C 2 + ; CH 3 + , CH 2 + , CH+, C+; C3H 5 2+ , C3H 4 2+ , C3H 3 2+ and C3H 2 2+ were determined from threshold up to 950 eV. Absolute partial ionization cross sections were obtained by charge weighted summing of all the observed partial ionization cross sections and by normalizing to a recent accurate determination of the total ionization cross section at 100 eV by Djuric et al. 1991. The absolute total ionization cross section curve obtained is in excellent agreement in shape and magnitude with the low energy data (〈200 eV) of Djuric et al. 1991 and the high energy data points of Schram et al. 1966.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426883
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Production and stability of oxygen cluster cations and anions, revisited (1991)
    Springer
    The European physical journal 20 (1991), S. 201-203 
    Details
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stoichiometric and non-stoichiometric, positive and negative oxygen cluster ions (n up to 70) have been produced in a crossed neutral beam/electron beam ion source. The abundance and stability of the ions formed have been analyzed with a double focussing sector field mass spectrometer in a series of experiments. Positive and negative ion mass spectra observed exhibit distinct abundance anomalies, however, at different cluster sizes. Abundance maxima and minima correlate with correspondingly small and large metastable fractions of (O2) n + and (O2) n − ions, respectively. (O2) n + ions may also lose up top=(n−1) monomers by collision induced dissociation with monotonously decreasing probability with increasingp. Metastable fractions determined for (O2) n − ions produced with appr. zero eV electrons are in general larger than those for ions produced with appr. 7 eV electrons. (O2) n − ions are also observed to decay via autodetachment, with lifetimes increasing with increasing cluster size. Finally, here we were able to prove that an apparent loss of the monomer fragment O (and higher homologues) observed in the metastable time regime is due to ordinary metastable monomer evaporation in the acceleration region. Moreover, we will also present here some new data and interpretation concerning the electron attachment cross section function for O2 clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543973
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Investigations on processes induced by single- and multiple-scattering of electrons in clusters involving excimer-induced fragmentation and a new metastable fragmentation channel observed for ArnO+* cluster ions (1993)
    Springer
    The European physical journal 26 (1993), S. 335-337 
    Details
    ISSN: 1434-6079
    Keywords: 36.40 ; 33.40.Hp ; 32.30.Bv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new metastable decay reaction of ArnO+ cluster ions produced by the electron impact ionization of argonoxygen clusters has been discovered, leading to the evaporation of more than two monomers in the metastable time regime. It is estimated that an energy of approx. 1 eV has to be released from the intramolecular to intermolecular modes prior to this metastable decay. In contrast to previously observed excimer-induced fragmentation of pure argon cluster ions, it has been concluded that the localized metastable state of an ionic rather than a neutral species is involved in the fragmentation. A reaction mechanism involving an electronic transition from the a2Π ArO+* (O(3P)-Ar+(2P)) excited state to the X4Σ− ArO+ (O+(4S)-Ar(1S)) ground state of the ArO+ complex ion within the cluster and subsequent release of considerable amount of vibrational energy to cluster modes is suggested to account for the observed fragmentation. Based on these measurements, a lifetime of approx. 2 µsis proposed for the excited state a2Π ArO+*.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01425708
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    Paper (German National Licenses)
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