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  • 1
    Electronic Resource
    Electronic Resource
    Surface analysis: x-ray photoelectron spectroscopy, Auger electron spectroscopy and secondary ion mass spectrometry (1984)
    s.l. : American Chemical Society
    Analytical chemistry 56 (1984), S. 373-416 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00269a026
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  • 2
    Electronic Resource
    Electronic Resource
    The role of cluster ion structure in reactivity and collision-induced dissociation: Application to cobalt/oxygen cluster ions in the gas phase (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 1276-1288 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ion/molecule reaction products of cobalt cluster ions have been characterized using mass spectrometric techniques. Atomic and bare-metal cluster ions were desorbed from foils by particle bombardment within a high-pressure (0.1–0.2 Torr) ion source. Sputtered metal cluster ions react with O2 to produce abundant stoichiometric or nearly stoichiometric cobalt(II) oxide cluster ions. The positive cluster product ions consist of three types: oxygen-deficient [Co(CoO)x]+ clusters, oxygen-equivalent [(CoO)x]+ clusters, and (in less abundance) metal-deficient [(CoO)xO]+ clusters. Tandem mass spectrometry and collision spectroscopy provide structural information about the more abundant cobalt cluster product ions. A major collision-induced fragmentation pathway for the oxygen-equivalent [(CoO)x]+ clusters is the loss of a CoO moiety to form [(CoO)x−1]+ fragments. A major collision-induced fragmentation pathway for the oxygen-deficient [Co(CoO)x]+ clusters is the loss of a cobalt atom to yield [(CoO)x]+ fragments. Geometric structures of the cobalt/oxygen cluster ions were calculated using a Coulomb plus Born–Mayer pair-potential model. The oxygen-equivalent cluster structures were found to be "globular'' cages, rings, or ladders. The oxygen-deficient cluster structures were found to be strained and "angular'' with protruding cobalt atoms. The structures are discussed in terms of the observed collision-induced fragmentations. The fragmentations are rationalized using an "instantaneous'' dissociation model of the collision-induced dissociation of the cluster ions. Preliminary trajectory calculations using classical dynamics support the use of this instantaneous dissociation model. The role of cluster ion structure in reactivity and collision-induced dissociation is discussed in terms of the experimental data and theoretical structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452217
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  • 3
    Electronic Resource
    Electronic Resource
    Ion molecule reactions of carbon cluster ions with D2 and O2 (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 715-725 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ion/molecule chemistry of laser-generated carbon cluster ions (C+n; n=3–19) has been studied using Fourier transform mass spectrometry. The ion/molecule reactions of mass-selected carbon cluster ions with D2 and O2 have been studied and reaction rates measured. Reactions of the primary product ions with D2 and O2 were also studied. The change in reactivity observed as a function of cluster size suggests a structural change from linear to monocyclic rings in the cluster ions between n=9 and 10. Evidence for the presence of two structural isomers for the C+7 cluster ion has also been observed and has been attributed to the existence of both a linear and cyclic form of the ion. MNDO calculations have also been used to obtain structural and thermodynamic information on possible reactant and product ions in an attempt to explain the differences observed in the ion/molecule reactions. The results from collision induced dissociation studies of the carbon cluster ions are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452274
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  • 4
    Electronic Resource
    Electronic Resource
    The σ* absorption peak at the oxygen 1s edge of O2: Exchange splitting, ultrafast dissociation, and atomiclike Auger spectra (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 4087-4092 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The x-ray absorption spectrum of solid O2 at the O 1s absorption edge is analyzed, using its polarization dependence and the Auger de-excitation spectra. Rydberg states are quenched in the solid, and the exchange splitting of the 1s ionization threshold (1.1 eV) can be observed. Below the ionization threshold, core electrons can be excited into unoccupied antibonding π* and σ* orbitals. We conclude from the relative intensities and from the polarization dependence, that the exchange splitting of the σ* final state is small (〈1 eV). This is confirmed by LDA calculations of core-excited states. The calculated σ* potential surfaces are repulsive, which explains the large width of this absorption peak. Because of ultrafast dissociation (∼5 fs), core hole decay is likely to occur at large interatomic distances. Auger spectra at the σ* absorption of O2 do indeed show peaks that would be expected for free core-excited oxygen atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466346
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  • 5
    Electronic Resource
    Electronic Resource
    The role of alternative geometries in alkali–halide clusters (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 5611-5616 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The relative importance of the cubic structures that were proposed to explain magic numbers for alkali–halide cluster ions from cluster sources is examined via total-energy calculations on nine-atom cluster ions of various optimized geometries. The relative energies of the planar, tetrahedral, quasioctahedral, lowest energy nonplanar nine-atom clusters for LiF, LiI, NaI, KI, RbI, CsI, NaF, NaCl, NaBr, and NaI are computed using Martin's Coulomb plus the Born–Mayer potential model. The most stable structure is invariably a slightly puckered plane. The relative energies of these clusters for LiF have also been tested using Hartree–Fock and density functional theory. Other comparisons are made for NaCl clusters and eight-atom LiF clusters. The computationally more tractable Born–Mayer potentials rather accurately predict the relative energies of the clusters in the ab initio calculations. The largest problem is too strong a repulsion between like atoms which overestimates the energy difference between the planar and quasioctahedral structure proposed by Morgan et al. These calculations suggest a greater population of noncubic structures for the larger and more polarizable alkali–halide cluster ions in beams from cluster sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449921
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of cluster ions produced by the sputtering or direct laser vaporization of group 13 metal (Al, Ga, and In) oxides (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 2578-2587 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The stabilities and reactivities of cluster ions generated from the fast-atom bombardment (FAB) or the direct laser vaporization (DLV) of the Group 13 metal oxides (Al2O3, Ga2O3, and In2O3) were examined by mass spectrometry. The nascent cluster ion distributions, fragmentations, and reactions were studied. The observed patterns of stability and reactivity were compared with the structures and heats of formation calculated from theoretical studies of aluminum oxide cluster ions using MNDO, Xα, and Born–Mayer pair potentials. The method of production of the metal oxide cluster ions, whether by FAB, DLV, or through the reaction of sputtered bare metal cluster ions with oxygen, had little influence on the abundance distribution observed. In agreement with the known M–O binding energies, a trend of increasing cluster oxidation state was observed in the abundance distributions of the cluster ions for decreasing metal atom z value. Dissociation of the oxide cluster ions occurred through the loss of particularly stable neutral fragments which together with theoretical considerations suggest a preference for particular parent cluster stoichiometries. Although gallium oxide and indium oxide cluster ions exhibited little reactivity toward oxidation agents, the aluminum oxide ions reacted readily with most oxidants. "Oxygen saturation'' effects were observed for the ions with 2 and 3 aluminum atoms. These saturation effects could be explained by the formation of structures in which the Al atoms are three-fold planar coordinated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459834
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  • 7
    Electronic Resource
    Electronic Resource
    Rearrangements in Negatively Charged Ammonium Nitrate Clusters (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 8261-8263 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100085a001
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  • 8
    Electronic Resource
    Electronic Resource
    Octahedral C48 and Uniform Strain (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 11018-11019 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100094a007
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  • 9
    Electronic Resource
    Electronic Resource
    Asymmetric localization of titanium in carbon molecule (C28) (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 9095-9097 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100202a003
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  • 10
    Electronic Resource
    Electronic Resource
    Paramagnetism of high nuclearity metal cluster compounds as derived from local density functional calculations (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7004-7007 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electronic structure of high nuclearity carbonylated Ni clusters [Ni32C6(CO)32]n− and [Ni44(CO)48]n− (n=0–6) has been investigated by means of all-electron calculations within the local density functional approach. The transition from the molecular to the metallic state was studied by determining the magnetic properties of bare and carbonylated clusters. The appearance of the metallic magnetic behavior is connected with the presence of metal atoms with bulklike coordination. The effect of interstitial impurity atoms in quenching the magnetic moment is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461045
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