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  • 1
    Electronic Resource
    Electronic Resource
    High pressure solid phases of benzene. II. Calculations of the vibration frequencies and evolution of the bonds in C6H6 and C6D6 up to 20 GPa (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 2633-2654 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The complete vibrational spectra of crystalline C6H6 and C6D6 have been calculated for the different pressure-induced solid phases recently determined at 293 K up to 25 GPa, and compared to Raman scattering data. The normal coordinate analysis has been carried out by using intermolecular Buckingham-type atom–atom interactions and the intramolecular force field of the free molecule. Results of such frequency calculations are compared to experimental values at ambient pressure. The variation of the relevant crystalline parameters is discussed to construct a model and calculate the vibrational frequencies under pressure. The quantitative fit of the frequency shift of the Raman active modes under pressure demonstrates the necessity of including different C–C and C–H (C–D) bond compressibilities within the benzene molecule. Such intramolecular distance variations which allow to estimate the frequency corrections for the totally symmetric (a1g) breathing modes, have been determined from the observed pressure-frequency dependence of these internal modes. The behavior of other nonsymmetric (e2g) internal modes which become comparatively weak under pressure, suggests a charge delocalization within—and possibly out of—the benzene ring, eventually leading to irreversible opening of the hexagonal cycle. This can be directly related to the irreversible transformation of benzene to a polymer which is observed after pressurization above 20 GPa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462014
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  • 2
    Electronic Resource
    Electronic Resource
    Transformation of benzene to a polymer after static pressurization to 30 GPa (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 6910-6915 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: After pressurization to 30 GPA, in a diamond anvil cell, benzene transforms, at room temperature, to a white solid which is stable at ambient pressure. We report here the infrared spectroscopy analysis performed under pressure and at ambient conditions. These preliminary results show that the transformation involves an opening of the benzene rings leading to a highly cross-linked polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458278
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanical strength of sapphire windows under pressure (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2719-2725 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Systematic tests of failure have been performed up to 700 MPa on 75 cylindrical sapphire windows of various thicknesses in the Poulter unsupported area geometry. Three distinct failure patterns are found to occur. The influence on the bursting pressure of the c-axis orientation, annealing, and fatigue are reported and discussed. Maximum working pressures are determined, as a function of the ratios of thickness and unsupported area diameter, to the window's diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145206
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  • 4
    Electronic Resource
    Electronic Resource
    Optical properties of zinc phosphide (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3282-3288 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical absorption edge of Zn3P2 has been measured by transmittance and photoconductivity at 300 K. The absorption coefficient in both polarizations is shown to follow the expected behavior for indirect gaps at 1.39 and 1.41 eV in parallel and perpendicular configurations. The high-absorption region has been measured in thin single crystals and the absorption coefficient is shown to agree with the optical constants derived from reflectivity for values of the absorption coefficient up to 105 cm−1. The optical properties and the behavior of photoconductivity are discussed in view of possible applications of Zn3P2 to solar energy conversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337719
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  • 5
    Electronic Resource
    Electronic Resource
    Two-dimensional defects in InSe (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 5267-5271 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-dimensional precipitates associated with stacking faults in layer semiconductors have previously been put forward to explain transport properties of these crystals, especially their remarkable electrical anisotropy. High-field cyclotron resonance behavior, among others, can be accounted for by two-dimensional accumulation layers in the vicinity of these defects. Direct evidence for the existence of these defects has been obtained by electron microscopy and x-ray microprobe analysis in indium selenide. Planar faults act like sinks for impurity atoms. This accounts for the unique behavior of layer compounds which exhibit intrinsic behavior (low apparent carrier concentration—high mobilities) even with high (100 ppm) initial doping levels. Optical, transport, and magnetotransport properties at low temperature can be explained along this model. As regards the applications of indium selenide to the photovoltaic conversion of solar energy, the existence of these defects explains most features of this semiconductor in this respect: (i) Its comparatively low effective diffusion length parallel to the c axis. (ii) p- to n-type switching under thermal annealing which allows fabrication of p-n junctions. (iii) Low apparent carrier density which precludes abrupt profiles for p-n structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338261
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  • 6
    Electronic Resource
    Electronic Resource
    X-ray diffraction of γ-Fe at high temperatures and pressures (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1795-1797 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Wire heating in diamond-anvil cells has been used to measure the pressure, temperature, resistance, and x-ray diffraction patterns of γ-Fe at pressures to 42 GPa and temperatures to 2340 K. The results can be described by a bulk modulus, K=127±8 GPa+2.2 (P/GPa). Extrapolation of these results to conditions of the earth's core yields a density in good agreement with shock compression and of about 15% higher than estimates of the preliminary reference earth model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342908
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical transport measurements in a gasketed diamond anvil cell up to 18 GPa (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 106-107 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A four-probe technique for electrical and photoelectrical measurements in a gasketed diamond anvil cell is presented. The special anvil profile and the method for the gasket preparation used in these experiments are described. Insulation and continuity of the electrical leads are shown to be satisfactory at least up to 18 GPa. As an example we report photoconductivity measurements in GaAs beyond crossover, under pressure, between direct and indirect band-gap configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139129
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  • 8
    Electronic Resource
    Electronic Resource
    A diamond anvil cell for IR microspectroscopy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2595-2598 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A large optical-aperture membrane diamond anvil cell designed for infrared spectroscopy is described. The cell offers definite advantages compared to existing systems. Other possibilities concerning x-ray diffraction analyses with the cells are mentioned. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145594
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  • 9
    Electronic Resource
    Electronic Resource
    Neutron powder diffraction at pressures beyond 25 GPa (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1735-1737 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Full structural studies of condensed media under high pressure by neutron powder diffraction have been limited in practice to 2–3 GPa for several decades. This range is in general too small to allow a precise determination of the pressure dependence of atomic coordinates. As a consequence, almost no direct measurements exist, for example, of the pressure dependence of the bond lengths in H2 and the planetary ices. In this letter, a technique is presented which makes it possible to pressurize samples of 35 mm3 volume up to 30 GPa and to collect neutron diffraction patterns in a few hours by time-of-flight techniques. This method provides data which can be treated by Rietveld profile refinement methods, as demonstrated on a sample of D2O ice VII at 26 GPa. This represents a tenfold increase of the pressure range over which refinable neutron diffraction data can be obtained and should have a number of applications in such fields as fundamental physicochemistry, and geo- and planetary sciences. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113350
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  • 10
    Electronic Resource
    Electronic Resource
    Phonon dispersion measurements at high pressures to 7 GPa by inelastic neutron scattering (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1557-1559 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel technique for the investigation of phonon dispersion curves by inelastic neutron scattering under high pressure is presented. The method uses tungsten carbide (WC) opposed anvils with a spheroidal pressure chamber, to compress samples embedded in NaCl by a hydraulic press of 250 tons capacity. The potential of the technique is illustrated by measurements of transverse acoustic phonons of germanium and Fe3Pt up to 7 GPa. Typical scan times were 2–3 h. It is shown that accurate determinations of mode Grüneisen parameters are possible and suggest that similar studies using this technique may be feasible for a wide range of solids to pressures beyond 10 GPa. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113645
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