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  • 1
    Electronic Resource
    Electronic Resource
    Inelastic incoherent neutron scattering study of the methyl rotation in various methyl halides (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2563-2575 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The inelastic incoherent neutron scattering technique has been applied in an energy range from 0.4 μeV to 60 meV to measure the rotational excitations of the methyl groups in polycrystals of CH3I, CH2DI, CD3I, CH3Br, CD3Br, and CH3Cl in a temperature range 5〈T[K]〈190. Tunnel splittings of the librational groundstate of 2.44 and 0.9 μeV were found for CH3I and CH3Br, respectively. Excitations to the higher excited librational states are identified via the temperature dependence and the isotope effects of the modes in the meV regime. The rotor–rotor coupling between neighboring methyl groups is found to be small. Thus single particle rotational potentials were derived from the observed eigenenergies. The potential strength increases going from the iodide via the bromide to the chloride. In CH3Br the rotational potential does not change on deuteration. In CH3I a very unusual increase in the rotational potential with deuteration is found. Besides the methyl librations, large amplitude motions around axes perpendicular to the molecular symmetry axis are observed at energies comparable to the methyl libration. The coupling of the methyl rotor to lattice modes modulating the strength of the orientational potential in CH3I gives rise to a peculiar temperature dependence of the tunnel splitting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452059
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  • 2
    Electronic Resource
    Electronic Resource
    Synthese und Charakterisierung von Poly(dichlorsilylen-co-dichlormethylen) und Poly(dimethylsilylen-co-2,2-propylen)
    Amsterdam : Elsevier
    Journal of Organometallic Chemistry 483 (1994), S. 183-186 
    Details
    ISSN: 0022-328X
    Keywords: Chlorination ; Chloropoly(carbosilanes) ; Photochemistry ; Poly(carbosilanes) ; Polymers ; Silicon
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-328X(94)87162-0
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  • 3
    Electronic Resource
    Electronic Resource
    Coupled pairs of quantum rotors in (CH3)2SnCl2: An inelastic neutron scattering study (1986)
    Springer
    The European physical journal 64 (1986), S. 447-452 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Rotational tunnelling and librations of the methyl groups in (CH3)2SnCl2 measured by inelastic neutron scattering are explained on the basic of coupled pairs of CH3 groups. The self and the interaction part of the rotational potential are determined to be (V 3,W 3)=(17.5 meV, 10.9 meV). Thus, in agreement with our expectation from the crystallographic structure, the frustrated coupling is realized in (CH3)2SnCl2 where the interactionW 3 counteracts the single particle potentialV 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312838
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  • 4
    Electronic Resource
    Electronic Resource
    Pressure dependence of tunneling and librational modes of coupled methyl groups in lithium acetate (1987)
    Springer
    The European physical journal 66 (1987), S. 75-81 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The pressure dependence of the tunneling and librational modes of the coupled methyl groups in lithium acetate dihydrate was studied by inelastic neutron scattering at liquid helium temperatures and the results compared with detailed model calculations. An increase of both the single particle and coupling potential parameters with increasing pressure was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312764
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  • 5
    Electronic Resource
    Electronic Resource
    Tunneling of coupled methyl groups in lithium acetate: The isotope effect (1989)
    Springer
    The European physical journal 76 (1989), S. 335-344 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We studied by high resolution inelastic neutron scattering the isotope effect of tunneling of coupled methyl groups in lithium acetate dihydrate (LIAC). Fully protonated, fully deuterated and mixed LIAC samples were investigated. The results are described by a simple model in which it is assumed that the single particle potential hindering rotation is strongly increased by deuteration, whereas the coupling potential is nearly unchanged. This allows to interpret the very strong isotope effect and also the spectra of the mixed compounds. The strong increase of the single particle potential by deuteration is tentatively explained by phonon mediated coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01321911
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of Coulomb interaction on transport through mesoscopic two-barrier structures (1991)
    Springer
    The European physical journal 85 (1991), S. 435-442 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the influence of the Coulomb interaction on the energy spectrum of a finite number of electrons in a geometrically confined quantum mechanical system. The spectrum is calculated numerically using the Slater determinants of the one-electron states as basis set. It is found to be dominated by the Coulomb repulsion when the system is large. Coulomb and exchange matrix elements for a given combination of four one-electron states are of the same order of magnitude. As a consequence, the energy difference between the ground states of the (N+1)- and theN-electron system is an order of magnitude smaller than each of the matrix elements, although being much larger than the separation of the one-electron energy levels. We discuss the importance of the interaction effects for the explanation of the recently observed resonant behavior of the electronic transport through quantum dots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01307641
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  • 7
    Electronic Resource
    Electronic Resource
    Nonlinear transport properties of quantum dots (1994)
    Springer
    The European physical journal 96 (1994), S. 201-206 
    Details
    ISSN: 1434-6036
    Keywords: 72.20.Ht ; 73.20.Dx ; 73.20.Mf ; 73.40.Gk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The influence of excited levels on nonlinear transport properties of a quantum dot weakly coupled to leads is studied using a master-equation approach. A charging model for the dot is compared with a quantum mechanical model for interacting electrons. The currentvoltage curve shows Coulomb lockade and additional finestructure that is related to the excited states of the correlated electrons. Unequal coupling to the leads causes asymmetric conductance peaks. Negative differential conductances are predicted due to the existence of excited states with different spins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313284
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  • 8
    Electronic Resource
    Electronic Resource
    Tunneling of coupled methyl groups (1985)
    Springer
    The European physical journal 59 (1985), S. 177-182 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method is developed which allows the calculation of tunneling frequencies for coupled methyl groups in strong or weak orientational potentials to any desired accuracy. The method is applied to two coupled methyl groups and the results of the calculation are compared with a recent experiment. The comparison allows conclusions on the strength and symmetry of the potential. A further important point is the prediction of coupling effects in rotational tunneling also in the limit of strong potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01725534
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  • 9
    Electronic Resource
    Electronic Resource
    Reducing firing of an early pottery making kiln at Batán Grande, Peru: A Mössbauer study (1999)
    Springer
    Hyperfine interactions 122 (1999), S. 163-170 
    Details
    ISSN: 1572-9540
    Keywords: archaeometry ; Mössbauer spectroscopy ; X-ray diffraction ; clays ; early ceramics ; authentic kiln ; reducing firing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Material from field firing experiments using a 2,700-year old Formative kiln at Batán Grande, Peru, was studied by X-ray diffraction and Mössbauer spectroscopy. The experiments explore the technology involved in producing the gray and black reduced ware for which Cupisnique and other Formative ceramics are justly known. During firing, the iron-bearing compounds in clays undergo characteristic changes which depend on kiln temperature and atmosphere. These changes can be observed in the Mössbauer spectra. By comparing spectra of an appropriate clay fired in field experiments and in the laboratory with the spectra of ancient ceramics, a description of Formative firing techniques in a reducing environment is attempted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012606025125
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  • 10
    Electronic Resource
    Electronic Resource
    Ausdehnung und maximaler Festkörperdurchsatz in mehrstufigen Wirbelschichtsystemen (1956)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 28 (1956), S. 633-638 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Es wird der Zusammenhang zwischen Festkörperdichte und Strömungsgeschwindigkeit in einem mehrstufigen Wirbelschichtsystem aus kugelförmigen Kunststoffteilchen (lonenaustauscher Permutit RS) und Wasser untersucht mit dem Ziel, allgemeine Gesetzmäßigkeiten für die Berechnungsgrundlalge zur Dimensionierung technischer Anlagen zu finden. Die Ergebnisse wurden nach der Gleichung von Brötz ausgewertet. In guter Übereinstimmung mit den Resultaten anderer Autoren ergab sich für den Brötz-Exponenten ein Wert von 4,34. Weiter wurde für den maximal erzielbaren Durchsatz in Abhängigkeit von der Strömungsgeschwindigkeit durch ein- und mehrstufige Wirbelschichtsysteme eine mathematische Beziehung abgeleitet. Die experimentellen Ergebnisse stehen in guter Übereinstimmung mit den aus der Formel berechneten.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330281003
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