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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 5 (1990), S. 143-154 
    ISSN: 1572-879X
    Keywords: NMR ; xenon ; coke ; zeolite ; extra-framework aluminium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolites coking has been studied by129Xe-NMR technique. The distribution of the coke is heterogeneous on the supercage surface at low cokage level. When coking increases up to 10% the supercages are lined with coke and the residual internal volume consists of narrow channels. Beyond 10% the coke also affects the external surface of the zeolites, with the formation of coke microcavities between the crystallites. This technique has also enabled us to show the role of extra-framework Al in the cracking activity of zeolites.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 24-28 
    ISSN: 0749-1581
    Keywords: Solid-state ; 87Rb ; NMR ; Quadrupole frequency ; Featureless lineshapes ; RbCaF3 ; Point defects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NMR nutation and quadrupole echo experiments were used to determine the quadrupole frequency (ωQ) of 87Rb (I = 3/2) in a single crystal of RbCaF3. Since RbCaF3 has a cubic unit cell above 195 K, there is no second-order quadrupole shift and the spectrum is rather featureless. By fitting the response of 87Rb, as a function of pulse duration, to the predicted response we were able to determine that the average ωQ/2π = 4.5 kHz in this sample. Discrepancies in the agreement between the theory and the experiment for the echo response were attributed to differential relaxation of the central and satellite transitions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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