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  • 1
    Electronic Resource
    Electronic Resource
    Dynamics of unimolecular dissociation of sodium cluster ions (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1492-1498 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the unimolecular dissociation dynamics of energy-rich sodium cluster ions, Na+n (5≤n≤40) by measuring the time evolution of their sequential monomer or dimer evaporative cooling. The experimental technique, tandem time-of-flight mass spectroscopy, measures the relative rate of competing dissociation channels from metastable ion clusters selected during an initial sampling time interval immediately following the creation of the ion cluster ensemble. Pulsed laser UV photoionization converts the distribution of neutral clusters emerging from a free-jet expansion to the distribution of ion clusters from which the initial selection takes place. For the smaller clusters, 3≤n≤14, we compare the measured dissociation rates with those calculated from a modified version of the RRK theory of unimolecular dissociation. In applying the theory we use monomer and dimer binding energies determined from theoretical calculation. For larger clusters, 15≤n≤40, the binding energies are not known, and we invert the calculation, using measured dissociation fractions, to determine the binding energies of the cluster ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456675
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  • 2
    Electronic Resource
    Electronic Resource
    Photodissociation of size-selected K+n clusters (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3022-3027 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photofragmentation studies are described for size-selected ionized potassium-atom clusters, generated in a supersonic expansion and analyzed with a tandem time-of-flight system. In the range n=3 to 41 the relative ion intensities in photofragmentation spectra reflect the relative stabilities of the ion products. Moreover the photon-energy dependence of the fragmentation patterns suggests that photodissociation proceeds rather via a fast sequential evaporation of neutral monomers than via a fission process. A value can be deduced for the mean binding energy per atom which is increasing with the cluster size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453944
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  • 3
    Electronic Resource
    Electronic Resource
    Laser-induced molecular desorption from size-selected nickel cluster carbonyl ions: Kinetics of the adsorption–desorption equilibrium (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2419-2426 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Gas phase reactivity of size-selected nickel cluster ions with carbon monoxide has been studied in a triple quadrupole mass spectrometer. Intensity distributions of the various nickel carbonyl ions are measured. Irradiation with a cw Ar+ laser beam demonstrates that efficient detachment of CO ligands occurs following single photon absorption by the metal cluster core. Laser-induced photodesorption is used to counterbalance the adsorption processes, in order to control the molecular coverage of the metal cluster. Time-resolved measurements of the kinetics of these two competing processes have been performed. A rate equation model is proposed which brings a detailed understanding of the kinetics and allows derivation of numerical values for the chemisorption rate constant and for the photoabsorption cross section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455036
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  • 4
    Electronic Resource
    Electronic Resource
    Adiabatic decomposition of mass-selected alkali clusters (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 5694-5699 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The decomposition of metastable photoionized mass-selected alkali clusters is investigated using a tandem time-of-flight spectrometer. Na+n and K+n are found to decompose mainly by the evaporation of either a single neutral atom or a neutral dimer in a time scale of about 10 μs. The predominant fragmentation channels are found to follow the adiabatic dissociation channels associated with the lowest energies accordingly to our CI calculations. In the light of our experimental and theoretical results a comparison between the different calculations of the absolute atomization energies available in the literature is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453544
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  • 5
    Electronic Resource
    Electronic Resource
    Photoionization of potassium clusters: Neutral and ionic cluster stabilities (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 229-238 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neutral potassium clusters of two different mass distributions generated either by a sonic or a conical nozzle were photoionized at several ionizing energies. By combining different nucleation conditions with several photoionization situations, variations of ion mass spectral patterns reflecting either neutral or ionic stabilities were obtained. The spectra show peaks or steps for those neutral and ionized clusters which contain 8, 20, and 40 electrons. These can be understood in terms of electronic shell structure for both neutral and ionized potassium clusters. However local irregularities appearing for the small cluster sizes reveal the influence of their geometrical structure. Moreover ionizing laser power dependencies taken at various photon energies were used to study fragmentation effects following ionization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453621
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  • 6
    Electronic Resource
    Electronic Resource
    Cohesive energies of K+n 5〈n〈200 from photoevaporation experiments (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7449-7456 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Evaporative cooling of internal energy rich potassium cluster ions K+n (5〈n〈200) is investigated within two well defined but quite different time windows. One of the time windows starts 1 μs after the photoexcitation of the cluster ions isolates one step in the evaporative cooling cascade. The experimental technique insures the complete determination of the dissociation channels. Tandem time-of-flight mass spectroscopy measures the relative rate of competing dissociation channels from ion fragmentation patterns. The corresponding neutral fragments are unambiguously determined after the reionization. Values for the dissociation energies of K+n (up to n=25) have been deduced from the unimolecular dissociation rates using statistical methods. These values are compared to Hückel calculations. The second time window starting just after the reexcitation of mass selected K+n is used to follow the steps of the photoinduced sequential evaporation from "hot'' clusters. The photofragmentation patterns for several photon energies give the atomization energies of ionized clusters up to n=200. Their evolution vs 1/R is compared to the droplet model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459418
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  • 7
    Electronic Resource
    Electronic Resource
    Adiabatic unimolecular dissociation of heterogeneous alkali clusters (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3732-3735 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The unimolecular dissociation of metastable photoionized mass-selected heterogeneous alkali clusters is investigated using a tandem time-of-flight spectrometer. NaK+n and Nan K+ are found to dissociate by evaporation of either a single neutral atom or a neutral dimer of the most abundant constituant. This behavior differs from the evaporation of heterogeneous neutral clusters which might always evaporate potassium in order to explain the sodium enrichment in the NaxKy neutral cluster distributions. This difference in the dissociation patterns of neutral and ionic heterogeneous clusters puts into evidence the influence of the charge in unimolecular dissociation processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453872
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  • 8
    Electronic Resource
    Electronic Resource
    Photothermodissociation of selenium clusters (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 10197-10203 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dissociation of selenium cluster ions containing from 7 up to 30 atoms has been studied using unimolecular decay of photothermoexcited clusters. Clusters containing more than 14 atoms evaporate Se6, Se7, and Se8 species, whereas smaller clusters with 7–10 atoms dissociate manly by Se2 loss. When the size increases, Se6 becomes the predominant channel showing a dissociation which evolves toward the bulk behavior. The changes in the observed channels correlate to changes in the dissociation energies which are deduced from the measured fractional dissociation rates and from the entropy contribution. Together with the previous study of tellurium clusters, this work provides comparative behavior of dissociation energies of group VI clusters and their convergence toward bulk properties. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481661
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  • 9
    Electronic Resource
    Electronic Resource
    Deplacement isotopique dans la raie de resonance D2 du rubidium. Inversion des valeurs de des isotopes 85Rb et 87Rb
    Amsterdam : Elsevier
    Physica B+C 82 (1976), S. 409-417 
    Details
    ISSN: 0378-4363
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0378-4363(76)90204-7
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  • 10
    Electronic Resource
    Electronic Resource
    Threshold behavior of laser ionization spectra for small potassium clusters
    Amsterdam : Elsevier
    Chemical Physics Letters 117 (1985), S. 365-370 
    Details
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0009-2614(85)85245-3
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