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  • 1
    Electronic Resource
    Electronic Resource
    Cyclohexane revisited: High pressure nuclear magnetic resonance rotating frame relaxation study of the dynamical solvent effects on the conformational isomerization of cyclohexane (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 2717-2723 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The main goal of this study is to extend the dynamic range of isomerization rates for cyclohexane in order to determine with high accuracy whether the barrier height to isomerization is pressure dependent. Therefore, the effect of pressure and temperature on the conformational isomerization of cyclohexane in carbon disulfide solvent has been investigated using the NMR (nuclear magnetic resonance) rotating frame relaxation technique. This technique, used for the first time in pressure studies of chemical exchange, allows the measurement of isomerization dynamics over a wide range of pressures and temperatures. By combining the rotating frame and NMR line shape techniques and generating the isoviscosity plots, it is shown that the barrier height to isomerization is independent of pressure. Since the experimental isomerization rate is accelerated by pressure, the viscosity dependence of the reduced transmission coefficient shows that the isomerization falls into the energy controlled (inertial) regime of the Kramers model in agreement with our earlier experimental findings. These experimental results, as interpreted in terms of stochastic models of isomerization reactions, indicate a strong collisional coupling and the presence of dynamical solvent effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462019
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  • 2
    Electronic Resource
    Electronic Resource
    Low energy Mott polarimetry of electrons from negative electron affinity photocathodes (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4161-4165 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present data on the spin polarization P and quantum yield Y of electrons photoemitted from negative electron affinity semiconductors, including GaAs(100), GaAsP(100) alloy, and strained GaAs layer epitaxially grown on a GaAsP(100) buffer. Near photothreshold the following values for P(Y) are, respectively, obtained: 26% (2.5×10−2), 40% (1×10−3), and 60% (1.5×10−4). We describe in detail the apparatus used containing a low energy (10–25 keV) Mott polarimeter. The system, completely fitted in a small volume (∼104 cm3) ultrahigh vacuum chamber, is intended as a test facility for characterizing candidate photocathode materials for spin polarized electron sources. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145364
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