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  • 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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  • 2
    Electronic Resource
    Electronic Resource
    Magic metastable decay of singly charged argon clusters (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 810-811 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Singly charged argon cluster ions produed by electron impact ionization of a neutral argon cluster beam are found to decay in the metastable time regime by a new mechanism leading to the ejection of "magic'' numbers of neutral argon atoms. The measured dependence of this new decay process on (i) the electron energy, (ii) cluster size and cluster properties, and (iii) the time since ion formation gives insight into the unique mechanism and the nature of this process. At a well-defined threshold energy of ca. 27 eV, the magic number loss mechanism occurs simultaneously with the well-known single monomer evaporation process which proceeds at all energies. Importantly, the new mechanism is the first known example of cluster ion metastability showing an exponential dependence on time, providing further evidence that the precursor parent cluster ion is produced in a specific energy state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460302
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  • 3
    Electronic Resource
    Electronic Resource
    Production and appearance size of multiply charged stoichiometric and nonstoichiometric SO2 cluster ions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1288-1289 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the first well resolved SO2 cluster ion spectrum showing doubly charged parent and fragment ions. The critical appearance size deduced for doubly charged SO2 clusters is n2=21 and for triply charged SO2 clusters n3=49. This result is compared with theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456135
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  • 4
    Electronic Resource
    Electronic Resource
    Size and temporal dependence of the metastable decay probabilities of ionized rare gas clusters (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3624-3627 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The temporal dependence of the metastable fractions have been measured for monomer evaporation from Ar+20, Ar+50, Ar+100, Kr+20, Kr+50, and Kr+100 ions produced by electron impact ionization of the respective neutral cluster beams. Size and temporal dependence are found to be in reasonable agreement with the predictions of the evaporative ensemble model. Small variations from the model predictions observed (in particular for the evaporation channel involving the cluster with the magic number 20) may be rationalized within this model by adjusting the appropriate parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461915
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  • 5
    Electronic Resource
    Electronic Resource
    Production and properties of singly and multiply charged Kr clusters (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3240-3245 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Kr clusters produced in a supersonic nozzle expansion have been studied by electron impact ionization mass spectrometry. Mass resolved spectra (with n up to 180) show two homologous series consisting of Kr+n and Kr2+n ions. The distribution of Kr+n ions shows distinct magic number effects, the observed abundance anomalies being very similar to the ones observed in Ar and Xe. This confirms the superior stability of closed-shell and -subshell icosahedral structures. Moreover, we have found evidence for the occurrence of Kr3+n and Kr4+n ions. It was possible to determine appearance sizes of these multiply charged cluster ions (yielding n2=69, n3=156, and n4=264), and to study the electron energy dependence of singly and doubly charged cluster ions (yielding a linear threshold law). These results are discussed in view of various theoretical considerations and previous results where available.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456898
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamics and kinetics of the metastable decay series: Ar3+*→Ar2+*→Ar+ (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 295-301 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Metastable decay of Ar+@B|3 produced by electron impact ionization of a supersonic Ar cluster beam has been investigated qualitatively and quantitatively with a double focusing sector field mass spectrometer. We present direct experimental proof that the observed metastable decay of Ar+*3 into Ar+ in the microsecond time regime proceeds predominantly via a sequential decay series Ar+@B|3→k3,2Ar+*2→ k2,1Ar+ involving the evaporation of a single monomer in each of these successive decays. The metastable decay rates deduced are very different, i.e., k3,2 =45 s−1 and k2,1 =680 s−1 at an ion acceleration voltage of 3 kV. Moreover, the metastable decay rates of Ar+@B|3 exhibit a strong dependence on time elapsed since electron impact production of the Ar+3, and on ion production parameters (i.e., size and internal excitation energy of the neutral precursor). For instance photodissociation (with visible laser light) of the neutral cluster beam leads to a dramatic increase of the observed metastable reaction rules yielding values of up to 100 000 3−1 in the μs time regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455469
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Production and properties of singly, doubly, and triply charged N2 clusters (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4289-4293 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Clusters of N2 molecules formed in a supersonic nozzle expansion have been studied by electron impact ionization mass spectrometry. Mass resolved spectra (with n up to 190) show three homologous series, i.e., consisting of (N2)+n, (N2)nN+, and [(N2)n N]2+ ions. The distribution of (N2)+n ions shows distinct magic number effects. Moreover, there is evidence for the existence of (N2)2+n and (N2)3+n ions. The critical appearance sizes of observed multiply charged cluster ions are (N2)2+99, (N2)99N2+, and (N2)3+215. These results are compared with theoretical predictions. Moreover, a study of the electron energy dependence of singly and doubly charged N2 cluster ions close to threshold (appearance energies) gives new insight into the ionization mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453787
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  • 9
    Electronic Resource
    Electronic Resource
    Near-threshold electron emission from impact of slow van der Waals clusters and fullerene ions on clean gold (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 8254-8261 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Atomically clean polycrystalline gold has been bombarded by slow cluster ions (N2)+n (n≤120), Ne+n (n≤100), and Cq+60,70 (q=1–4) at kinetic energies from the apparent electron emission thresholds up to 6 kV times the cluster charge (qe). The resulting electron yields have been derived from the corresponding electron emission statistics. Grossly different electron yields were found for different cluster species of about equal masses and velocities, which is attributed to different partitions of the initial cluster kinetic energy among (a) inelastic binary collision processes involving cluster constituents and surface atoms, and (b) intramolecular vibrational excitation in the cluster ions (where possible). We found emission threshold velocities of ∼1×104 m/s, which is a lower velocity than where emission was observed in most other studies previously conducted. For (N2)+n cluster ions, clear evidence for a nonlinear behavior (i.e., increasing electron emission per cluster constituent with increasing cluster size) has been found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465651
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  • 10
    Electronic Resource
    Electronic Resource
    Self-consistent determination of fullerene binding energies BE (C+n–C2), n=58⋅ ⋅ ⋅44 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 1225-1231 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using recently measured accurate relative partial ionization cross section functions for production of the C60 fragment ions C+58 through C+44 by electron impact ionization, we have determined the respective binding energies BE(C+n–C2), with n=58,...,44, using a novel self-consistent procedure. Appearance energies were determined from ionization efficiency curves. Binding energies were calculated from the corresponding appearance energies with the help of the finite heat bath theory. Then using these binding energies we calculated with transition state theory (TST), the corresponding breakdown curves, and compared these calculated ones with the ones derived from the measured cross sections. The good agreement between these breakdown curves proves the consistency of this multistep calculation scheme. As the only free parameter in this procedure is the binding energy C+58–C2, we studied the influence of different transition states chosen in the determination of this binding energy via TST theory and iterative comparison with breakdown curve measurements. Based on this study we can conclude that extremely loose transition states can be confidently excluded, and that somewhat looser transition states than those used earlier result in an upward change of the binding energy of less than 10% yielding an upper limit for the binding energy C+58–C2 of approximately 7.6 eV. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471708
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