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  • 1995-1999  (9)
  • 1985-1989  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    Q dependence of rotational excitations of CH4 molecules in argon (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 400-405 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotational excitations of CH4 molecules, matrix isolated in solid argon, are observed with inelastic neutron scattering (INS). In the argon matrix the orientational crystalline field Vc(Ω) leads to weakly hindered rotation. Experimental data are compared with the predictions of the "Extended James–Keenan model'' for solid CH4 II. Deviations from complete orientational disorder are studied via the Q dependence of the scattered intensities. The transition energies for CH4 in Ar differ considerably from the corresponding transition energies in solid CH4 II due to the stronger crystalline field, while the transition matrix elements seem to be rather similar. The parameters β4=7.5 and β6=−25 of the expansion of the crystalline field into octahedral rotor functions are estimated from the experimental data and compared with predictions, based on different empirical potentials between nonbonding atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456488
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  • 2
    Electronic Resource
    Electronic Resource
    On the structure of solid Ca(ND3)x; with x(approximate)6 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1167-1172 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bcc structure of Ca(ND3)5.7 is found to be stable down to He temperatures. The crystal is characterized by frozen-in orientational disorder and also positional disorder of the ND3 molecules. The latter may be explained by a distribution of octahedrally coordinated and tetrahedrally coordinated Ca ions. The relation of occupation numbers with stoichiometry cannot be made quantitatively, however. There are no indications of a significant departure from the geometry of a free ammonia molecule in the solid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457189
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Interdiffusion in NiMnSb/V/NiMnSb: X-ray and neutron reflectivity investigation of ion beam sputtered trilayer systems (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5146-5151 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The new trilayer system NiMnSb/V/NiMnSb on MgO(001) was investigated by means of vibrating sample magnetometry (VSM), x-ray, and neutron reflectivity. VSM revealed a coercive field Hc=23 Oe and a hysteresis loop similar to that of an uncoupled ferromagnet. The x-ray and neutron reflectivity data proved that interface roughnesses of 10 Å are present. A detailed analysis yielded significant interdiffusion at the NiMnSb/V interfaces which is one possible explanation for the weak magnetoresistance effect measured in similar NiMnSb-based multilayer systems. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371491
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray characterization of buried allotaxially grown CoSi2 layers in Si(100) (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5823-5830 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An x-ray study of the interface morphology and lattice parameters of buried expitaxial CoSi2 layers in Si(100) is presented. Specular reflectivity, diffuse and crystal truncation rod scattering, together with grazing incidence diffraction yield detailed information about the interface quality and lattice mismatch. It turns out that the CoSi2 interfaces are considerably smoothened by an annealing step at 1150 °C. Also the in-plane correlation length of the roughness increases yielding laterally smoother interfaces. While the perpendicular lattice parameter is between that of a free relaxed and a pseudomorphic structure and a linear contraction as function of the annealing temperature is obtained, grazing incidence diffraction reveals the opposite effect for the in-plane lattice mismatch. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367439
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  • 5
    Electronic Resource
    Electronic Resource
    Rotational excitations of a symmetric top in cubic orientational potentials: CH3D matrix-isolated in argon and krypton (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 6880-6890 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Measurements with inelastic neutron scattering of the rotational spectra of the symmetric top molecule CH3D as substitutional impurities in crystalline argon and krypton are presented. The energy of the J=1 doublet is shifted by 33% and 27% respectively, compared to the completely free rotor. Spin-rotational wave functions for the free CH3D rotor are constructed and used for the calculation of the dependence of the scattered intensities on momentum transfer. In contrast to the CH4 molecule, the center of mass does not coincide with the position of the carbon atom in the case of the CH3D molecule. However, energies and intensities can only be explained if this fact is disregarded. The spin conversion behavior has been studied on a CH3D/argon sample within the temperature range 1.5 K≤T≤5 K. Two different mechanisms for the conversion process (libron-phonon process and Raman process) are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470719
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  • 6
    Electronic Resource
    Electronic Resource
    Ammonia rotations in ytterbiumhexaammine (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 1122-1128 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The results of inelastic neutron scattering experiments on ytterbiumhexaammine are presented. At temperatures below 35 K, the dominant dynamical process is a uniaxial rotation of the ammonia in hindering potentials of about 35 meV. At higher temperatures, another type of ammonia motion is observed, which is described as reorientations of entire Yb(NH3)x complexes (x≈6). © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469170
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  • 7
    Electronic Resource
    Electronic Resource
    Rotational excitations of a symmetric top in cubic orientational potentials. II. CHD3 matrix-isolated in argon (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 1764-1769 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Inelastic neutron scattering has been performed on CHD3 molecules matrix isolated in solid argon. Four inelastic lines have been observed within the energy transfer range 0≤(h-dash-bar)ω≤2.5 meV. The corresponding energy level scheme and the line intensities are explained in terms of a model based on a completely free rotation of the CHD3 molecule. An expression for the double differential neutron scattering cross section of the free CHD3 rotor is derived. In spite of a line shift of 44% with respect to the free rotor, no crystal field splitting was observed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472051
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  • 8
    Electronic Resource
    Electronic Resource
    Orientational order and rotational dynamics of the amide ions in potassium amide. II. Quasielastic neutron scattering (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 3559-3567 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ionic molecular crystal potassium amide (KNH2) was investigated by means of quasielastic incoherent neutron scattering (QNS). In the orientationally disordered cubic and tetragonal high–temperature phases as well as in the ordered monoclinic phase reorientational motions of the amide ions (NH2−) are resolved in a frequency range of three orders of magnitude. The QNS spectra are well explained by reorientational models for each phase. Furthermore, the results are compared to structural data and findings of other spectroscopic methods. Finally, a consistent picture of structure and dynamics of all three phases of potassium amide is obtained. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476951
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  • 9
    Electronic Resource
    Electronic Resource
    Rotational excitations in CH4 II: Effect of Kr impurities (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6465-6473 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The perturbation of the partial orientational order in CH4II caused by dilution with Kr(xKr≤0.20) has been studied with inelastic incoherent neutron scattering. Both, the lines assigned as rotational tunneling and almost free molecular rotation, display a characteristic asymmetric broadening which gets more pronounced with increasing Kr concentration. At low Kr concentrations (xKr≤0.05) the tunneling spectra are well explained by a model which is based on a statistical distribution of local rotational potentials. In this model only the number of Kr atoms replacing orientationally ordered CH4 nearest neighbors is relevant for the local potential at the sites of tunneling molecules. The different local symmetries are not considered in the model. It was not possible to formulate a quantitative model for the scattering from molecules at nearly free rotor sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452437
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  • 10
    Electronic Resource
    Electronic Resource
    Rotational excitations and orientational disorder in solid mixtures of CH4 and Kr (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2204-2210 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The orientational disorder in a solid solution of methane and krypton (27% Kr) has been studied with inelastic neutron scattering. The spectra display a transition from diffusive high temperature rotations to rotational excitations of molecules with frozen-in orientational disorder at low temperatures. Of particular interest is a relatively sharp feature at an energy transfer of 0.78 meV which both broadens and shifts with increasing temperature. A simple model is based on a statistical distribution of local potentials due to the presence of Kr atoms and the state of excitation of the molecules. Finally, the isotope effect of the rotational excitations has been investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451114
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