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  • 1995-1999  (3)
  • 1990-1994  (21)
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  • 1
    Electronic Resource
    Electronic Resource
    Atomic force and scanning tunneling microscopy analysis of palladium and silver nanophase materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 546-551 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomic force and scanning tunneling microscopy images of nanophase palladium and silver materials taken on various length scales are presented. The samples show a conformational packing of individual nanometer-sized clusters. In the case of silver, islands of clusters are observed on micrometer length scales. The islands are very flat and separated by deep crevices. The grains (clusters) within the islands are closely packed with shapes adjusting to the neighboring grains. The islands are compact, either equiaxed or oblong in shape. Average island diameters of 200–300 nm and average grain sizes of 20–50 nm were measured. The height variations on the islands are between 5 and 15 nm. The crevices are between 200 and 400 nm deep. In the case of palladium, the clusters are more uniformly packed and do not appear to be agglomerated in islands. Palladium grain sizes typically of 15 nm were measured along with corrugations of 10 nm in the closely packed areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357109
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  • 2
    Electronic Resource
    Electronic Resource
    Luminescence studies of localized gap states in colloidal ZnS nanocrystals (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2841-2845 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ZnS nanoparticles were prepared by chemical precipitation of Zn2+ with sulfur ions in aqueous solution. The ultraviolet-excited samples reveal detailed structure in the luminescence spectra. A doublet pattern observed in the long wavelength region is attributed to the coexistence of the two crystalline forms in ZnS particles. The visible luminescent radiation at 590.1 nm is due to Mn impurities. The dominant emission band at short wavelengths exhibits a quadruple fine structure with peaks located at 416.1, 423.9, 430.1, and 437.8 nm which are identified with optical transitions arising from vacancy and interstitial sites for both Zn and S atoms. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368425
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Manipulation of graphitic sheets using a tunneling microscope (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 4695-4699 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Folding and unfolding of atomic layers has been performed at step edges of graphite using a scanning tunneling microscope. The technique consists of modulating the distance or bias voltage between the microscope tip and the sample when scanning selected areas. Calculation of the energies involved in the manipulations shows that tip-sample vibration can account for tearing and folding of graphitic layers. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367257
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A Cluster Space Calibration Scheme for Synthetic Wind Statistics Calculated with a Mesoscale Model and its Application to Regional Wind Climate Studies (1999)
    Springer
    Meteorology and atmospheric physics 71 (1999), S. 189-203 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary ¶A scheme for calibrating an ensemble of wind fields computed by a mesoscale model in order to generate synthetic wind statistics is described. It is based on two main points. The first is to exploit the power of a mesoscale model to determine wind fields over complex terrain for different weather situations classified by cluster analysis. The second is to use all the information in the cluster analysis, i.e., the centroid values as well as the internal standard deviations of the clusters, to determine a cluster space distribution at each grid point in the model domain. The latter makes calibration possible if reliable measurements are available at the position of one of the grid points. The accuracy of the calibration is increased by splitting the cluster spaces into several parts. Combining both the modelled mesoscale wind fields and the method of split cluster spaces leads to a spatial transformation of the calibration from the calibration point to each grid point in the model domain. A validation of the scheme is carried out with measurements at grid points other than the calibration point and reveals remarkable improvements in the accuracy of the model wind statistics, especially with regard to wind speed distributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007030050055
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Vote of no confidence (1990)
    [s.l.] : Nature Publishing Group
    Nature 347 (1990), S. 419-419 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-The crisis at London's Natural His-tory Museum, which erupted when the corporate plan was announced on 23 April this year, has now lasted more than four months and shows no sign of ending. The essence of this crisis is that the plan will result, whatever its stated intentions, in narrowing the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/347419a0
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  • 6
    Electronic Resource
    Electronic Resource
    Static and dynamic forces on a permanent magnet levitating between superconducting surfaces (1993)
    Springer
    Journal of low temperature physics 93 (1993), S. 85-100 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A charged magnetic microsphere (radius 100 µm) is levitating inside a superconducting niobium capacitor. Because of its charge of about 1 pC, oscillations about the equilibrium position can be excited and detected electrically. The properties of this oscillator are investigated in order to study the static and dynamic forces of magnetic levitation. We find resonance frequencies between 200 Hz and 600 Hz. The resonance frequency and the damping are amplitude dependent due to nonlinear return forces and nonlinear friction, respectively. At small amplitudes the Q value is about 106 in vacuum. A dc field can be applied to change the equilibrium position and consequently the resonance frequency. From the data the spatial dependence of the static force and of the dynamic stiffness can be determined and an empirical relation between both is established. Quite often, we find a hysteretic behavior of the static force whereas the stiffness is a reversible function of the position. Amplitude dependent damping is observed both in the decay of the free oscillations and in the dependence of the amplitude of the forced oscillations on the driving force.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682282
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Scanning tunneling microscopy and spectroscopy for cluster and small particle research (1991)
    Springer
    The European physical journal 19 (1991), S. 287-292 
    Details
    ISSN: 1434-6079
    Keywords: 36.40 + d ; 73.40 Gk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Scanning tunneling microscopy (STM) and spectroscopy (STS) are new methods to investigate atomic arrangements and electronic structures of clusters and small particles of atoms. In this paper we review recent developments in this field, in particular the work from our laboratory. We show studies of single adatoms, small clusters and larger particles of platinum and a trimer of aluminum imaged with atomic resolution on highly-orient ed pyrolytic graphite. We find different isomeric structures for clusters of a specific size. Taking the substrate lattice as reference we determine bond lengths and angles for the clusters. We find that adsorbed Pt-particles have a strong influence on the substrate. Periodic charge density modulations on the graphite lattice surrounding the particles are observed. We also discuss recent STS experiments which showed Coulomb blockade in electron tunneling. A silicon-oxide-graphite tip-junction is used where a mesoscopic insulating area containing trap levels for temporary electron storage is responsible for the blockade of single electron transport. Such an ultra-small insulator capacitor shows large voltage steps in current-voltage characteristics and quantization of the tunneling current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01448313
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  • 8
    Electronic Resource
    Electronic Resource
    Scanning tunneling microscopy of sputtered aluminum particles (1991)
    Springer
    The European physical journal 19 (1991), S. 323-325 
    Details
    ISSN: 1434-6079
    Keywords: 36.40. + d ; 61.16.Di
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The scanning tunneling microscope is an ideal tool to study the local geometric and electronic structure of single supported metal clusters. Our experimental setup consists of an extraction type ion gun combined with a quadrupol mass spectrometer to deposit mass-selected metal cluster. ions. First results showing scanning tunneling microscopy pictures of sputtered aluminum clusters are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01448321
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  • 9
    Electronic Resource
    Electronic Resource
    A scanning tunneling microscope study of single platinum atoms, platinum dimers and trimers on highly-oriented pyrolytic graphite (1991)
    Springer
    The European physical journal 19 (1991), S. 319-321 
    Details
    ISSN: 1434-6079
    Keywords: 36.40 + d ; 61.16.Di
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report a topographic study of platinum clusters on highly-oriented pyrolytic graphite (HOPG) using a scanning tunneling microscope operating in air. The particles were produced by evaporation of platinum onto the graphite-surface in high vacuum. The simultaneous finding of single platinum atoms, clusters and small particles on an otherwise clean and atomically flat surface shows that the platinum-HOPG surface interaction is strong enough to yield stable images of Pt atoms and yet is not strong enough to annihilate the Pt-Pt interaction. Small flat platinum clusters on HOPG can be imaged with atomic resolution of the cluster and the surrounding graphite lattice. We show the adsorption site distribution for the monomers. The Pt-dimers show a very broad bond length distribution on graphite with an average of 2.46 Å. We found two types of Pt-trimers, one which is almost linear and one of triangular form. The average nearest neighbour distance of the trimers is 2.61 Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01448320
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  • 10
    Electronic Resource
    Electronic Resource
    Alkali-hydride water cluster ions (1993)
    Springer
    The European physical journal 26 (1993), S. 204-206 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 81.10.Bk ; 35.20.Wg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using a CO2 laser we have desorbed LiOH and NaOH from a solid target into an expanding inert gas jet pulse. Subsequently the beam was ionized by photons from a UV laser. Surprisingly, we observed in mass spectra metal water clusters and metal-hydride water clusters. For the metals M=Li, Na we find that the [M(H2O)n]+ peaks are dominant for small clusters, while for large clusters (n〉20) the [MH(H2O)n]+ peaks are dominant. This indicates that the clathrate (H2O)20 may play an important role in the formation of metallo-water clusters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01429145
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