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  • 1
    Electronic Resource
    Electronic Resource
    Isomers of niobium clusters: Direct spectroscopic evidence (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1476-1477 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have reproduced kinetics results indicating that niobium clusters in the size range Nb9–Nb12 are produced in two isomeric forms which possess widely different rates reactivity toward D2. We have exploited this difference in reactivity to record photoionization efficiency spectra of the unreactive forms of Nb9, Nb10, and Nb12 as well of a mixture containing predominantly the reactive forms. We find that the photoionization thresholds measured for Nb9 and Nb12 with the reactive forms of these species depleted via reaction with D2 are shifted to higher energies compared those recorded without D2 present. The photoionization threshold energies for both unreactive and reactive forms of Nb10 are approximately equal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459159
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  • 2
    Electronic Resource
    Electronic Resource
    Photoinduced charge-transfer dissociation in van der Waals complexes: Na2⋅⋅⋅(ClCH3)n (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8628-8630 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462268
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  • 3
    Electronic Resource
    Electronic Resource
    Photoionization studies of niobium clusters: Ionization potentials for Nb2–Nb76 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5760-5767 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoionization efficiency (PIE) spectra for niobium clusters up to Nb76 are measured using laser ionization time-of-flight mass spectrometry. Ionization potentials (IPs) assigned from the PIE spectra evolve with the same general pattern observed for other transition metal clusters (Mn) studied to date: a rapid yet nonmonotonic decrease in IP to n(approximately-equal-to)15 followed thereafter by a relatively slow and smooth evolution. The measured IPs evolve with cluster radius R according to the predictions of the conducting spherical droplet model if the limiting (R→∞) IP is chosen to be 0.5 eV lower than the bulk polycrystalline work function. Kinetics experiments using D2 as the coreactant indicate the existence of two structural forms, one highly reactive, one relatively unreactive for clusters in the size range Nb9–Nb12, with the reactive forms predominant in each case. PIE spectra for Nb9–Nb12 were recorded using sufficient D2 added to the cluster source to selectively titrate the reactive forms of these clusters, leaving the unreactive forms as the predominant isomers. It is found that the unreactive forms of Nb9 and Nb12 possess higher IPs than those of the reactive forms, while both forms of Nb10 possess approximately the same IP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459570
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  • 4
    Electronic Resource
    Electronic Resource
    Near-threshold photoionization of nickel clusters: Ionization potentials for Ni3 to Ni90 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 94-104 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The threshold photoionization efficiency (PIE) curves for nickel clusters in the size range Ni3 to Ni90 have been measured by laser photoionization with detection by time-of-flight mass spectrometry. Both warm (≤298 K) and cold (≤77 K) clusters have been studied. The PIE curves for 298 K clusters display thermal tails, while these tails are smaller for cold clusters. Cluster ionization potentials (I.P.s) have been determined by two methods: the Watanabe procedure and linear extrapolation of the PIE curves. Dramatic dependence of I.P. on cluster size is found for clusters smaller than 11 atoms, while the I.P.s of larger clusters decrease relatively smoothly and nearly monotonically from 5.84 eV for Ni11 to 5.56 eV for Ni90. The I.P.s for clusters larger than Ni40 show the linear dependence on reciprocal radius (R−1) predicted by the conducting spherical drop model of small particle I.P.s, but do not fit the model quantitatively unless the limiting (R−1→ 0) work function is reduced by 0.46 eV from the bulk polycrystalline value. The differences between the thermal tails of the room temperature and 77 K PIE curves diminish with increasing cluster size, suggesting a reduced difference between neutral and ionic structures for larger clusters. In general, there is poor agreement between our experimental results and theoretically calculated I.P.s for small nickel clusters, with the exception of the recently reported tight-binding theory results of Pastor et al. [Chem. Phys. Lett. 148, 459 (1988)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459467
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  • 5
    Electronic Resource
    Electronic Resource
    Photoionization studies of transition metal clusters: Ionization potentials for Fen and Con (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1533-1539 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoionization efficiency (PIE) spectra for cold iron clusters (Fe6–Fe90) and cobalt clusters (Co3, Co7–Co92) have been measured using a tunable ultraviolet laser combined with time-of-flight mass spectrometry. Vertical ionization potentials (IPs) assigned from the observed photoionization thresholds decrease rapidly but nonmonotonically for both Fen and Con up to n≅20, beyond which IPs evolve more slowly and smoothly. The measured IPs for both iron and cobalt clusters are lower than those predicted by the conducting spherical droplet model. The evolution of IP with increasing cluster radius R is observed to occur more gradually than the R−1dependence predicted by this model. This suggests that the Fermi energy for clusters in this size range decreases with increasing cluster size. The shapes of the PIE spectra near threshold are observed to continuously evolve with increasing cluster size, with the smallest clusters displaying photoionization efficiencies which rapidly increase with energy above threshold, and larger clusters displaying spectra with more gradual slopes. It is proposed that this trend reflects the evolution in the density and distribution of low-lying electronic states which occurs with increasing cluster size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459131
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  • 6
    Electronic Resource
    Electronic Resource
    Photoinduced charge-transfer dissociation in van der Waals complexes. II. Na2...ClCH3, Na2...(ClCH3)2, and Na...FPh (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 5431-5443 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: van der Waals complexes Nam...(XR)n (R=CH3 and Ph; X=Cl and F) have been generated by crossing a beam of Na with a supersonic jet of halide molecules XR seeded with Ar. The complexes were identified and measured by photoionization time-of-flight mass spectrometry. Tunable visible radiation (530–680 nm) was used to measure the photodissociation spectrum (an "action spectrum'') of these clusters. The peak cross section for photodissociation of Na2...(ClCH3)n (n=1 and 2) was found to be large (∼6 A(ring)2) with its maximum at 635 nm for n=1 and at 615 nm for n=2. These peak wavelengths suggest that the primary route for photodissociation is excitation of the Nam followed by charge-transfer dissociation: Na2...(ClCH3)1,2 + hυ → [Na*2...(ClCH3)1,2]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464892
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  • 7
    Electronic Resource
    Electronic Resource
    Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2901-2903 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the preparation of highly monodisperse ZnO nanoparticles using poly(vinyl pyrrolidone) (PVP) as the capping molecules. The surface-modified ZnO nanoparticles were found to be remarkably stable. The optical absorption shows distinct excitonic features. Markedly enhanced near-band-edge ultraviolet photoluminescence and significantly reduced defect-related green emission were also observed. We attribute this observation to the nearly perfect surface passivation of the ZnO nanoparticles by the PVP molecules. The third-order nonlinear optical response of these PVP-capped ZnO nanoparticles in a dilute solution was found to be significantly larger (by at least two orders of magnitude) than that of the bulk ZnO. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126511
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  • 8
    Electronic Resource
    Electronic Resource
    Experimental and Theoretical Studies of Small Homoatomic Phosphorus Clusters (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 1418-1423 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100005a009
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  • 9
    Electronic Resource
    Electronic Resource
    Generation of fullerenes and metal–carbon clusters in a pulsed arc cluster ion source (PACIS) (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 6577-6581 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By combining a pulsed arc cluster ion source with a reflection time-of-flight mass spectrometer, we have produced and detected in situ fullerene cations as well as vanadium–carbon cluster cations. The cluster arrival time distributions favor the "fullerene road'' mechanism for fullerene growth. The formation of fullerene cations was found to be strongly dependent on the discharge and nozzle conditions. Fullerene C+60/C+70 were preferentially produced by optimizing these conditions. Vanadium–carbon cluster cations were produced and detected by using a composite electrode (V2O5/graphite). While the metallocarbohedrene V8C+12 could be produced with a reasonable intensity, it was not dominant under our experimental conditions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471377
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  • 10
    Electronic Resource
    Electronic Resource
    Studies of C60-metal reactions in the laser-ablation plasma of C60/M2O3 (M=La, Y, Eu, Gd) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 189-192 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reactions of excimer laser (XeCl, 308 nm) vaporized and excited fullerene C60 with La, Y, Eu, and Gd were carried out in mixtures of C60/La2O3, C60/Y2O3, C60/Eu2O3, and C60/Gd2O3. The reaction products M@xaC60, M@xaC60-2n and M@xaC60+2m (M=La, Y, Eu, and Gd) were identified by a reflectron type time-of-flight mass spectrometer (RTOFMS). The products were subjected to reactions with H2O, O2, and N2O in a pick-up source. The metallofullerenes were found to be nonreactive toward H2O, N2O, and O2. This gives support to the endohedral nature of the metallofullerenes. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469390
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