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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 28 (1993), S. 67-72 
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 71.28.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Rare earth clusters of europium, thullium and ytterbium were generated by gas aggregation technique and probed by photoionization mass spectrometry. Their relative intensities in mass spectra have shown that their stabilities are governed by compact geometrical structures. The addition of oxygen gas in the nucleation region was used to produce the reactive nucleation. Several stages of oxidation were observed as a function of oxygen pressure up to saturation. For the maximal degree of oxidation the observed oxide ion compositions enable one to follow the valence of metal atom in its oxide as cluster size increases. This exhibits a divalent to trivalent valence change with cluster size. Moreover it emerges from the data that the divalent to trivalent transition for Tm, Yb, and Eu occurs at different size values.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 3 (1986), S. 121-129 
    ISSN: 1434-6079
    Schlagwort(e): 36.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Electronic structure effect in small metallic clusters up ton=15 are investigated through three series of experiments performed on one-valence-electron-atom clusters and two-valence-electron ones. In these experiments the cluster molecular beam is probed by photoionization mass spectroscopy, either by using a tunable laser source for alkali clusters or by synchrotron radiation for mercury ones. With alkali clusters the results are related to fragmentation effects, ionization potential measurements and photoionization efficiency curve profile analysis in the threshold region. The similar behavior of the homogeneous and heterogeneous clusters and the comparison with theoretical models suggest that forn≧3 the valence electrons are partially delocalized. This similarity against the electronic structure is not found in the nucleation process which generates homogeneous and heterogeneous clusters with a strong difference in their respective abundances. For mercury clusters the evolution with size for excitation spectra of two autoionizing lines is obtained up ton=8. Results show that they do not have a metallic character. This is also supported by the observation of small doubly charged mercury clusters forn≧5 which are stable against the Coulomb explosion.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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