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  • 1
    Electronic Resource
    Electronic Resource
    Hybrid modes in a circular waveguide with an impedance wall (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2572-2573 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A general characteristic equation is derived in order to determine the propagating modes inside a circular waveguide with an impedance wall. Furthermore, corrections to the eigenvalues reported by Mohsen and Hamid are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339428
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    Paper (German National Licenses)
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  • 2
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    Unconventional hydrogen bonding to organic ions in the gas phase: Stepwise association of hydrogen cyanide with the pyridine and pyrimidine radical cations and protonated pyridine (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-08-06
    Description: Equilibrium thermochemical measurements using the ion mobility drift cell technique have been utilized to investigate the binding energies and entropy changes for the stepwise association of HCN molecules with the pyridine and pyrimidine radical cations forming the C 5 H 5 N + · (HCN) n and C 4 H 4 N 2 + · (HCN) n clusters, respectively, with n = 1–4. For comparison, the binding of 1–4 HCN molecules to the protonated pyridine C 5 H 5 NH + (HCN) n has also been investigated. The binding energies of HCN to the pyridine and pyrimidine radical cations are nearly equal (11.4 and 12.0 kcal/mol, respectively) but weaker than the HCN binding to the protonated pyridine (14.0 kcal/mol). The pyridine and pyrimidine radical cations form unconventional carbon-based ionic hydrogen bonds with HCN (CH δ+ ⋯NCH). Protonated pyridine forms a stronger ionic hydrogen bond with HCN (NH + ⋯NCH) which can be extended to a linear chain with the clustering of additional HCN molecules (NH + ⋯NCH··NCH⋯NCH) leading to a rapid decrease in the bond strength as the length of the chain increases. The lowest energy structures of the pyridine and pyrimidine radical cation clusters containing 3-4 HCN molecules show a strong tendency for the internal solvation of the radical cation by the HCN molecules where bifurcated structures involving multiple hydrogen bonding sites with the ring hydrogen atoms are formed. The unconventional H-bonds (CH δ+ ⋯NCH) formed between the pyridine or the pyrimidine radical cations and HCN molecules (11–12 kcal/mol) are stronger than the similar (CH δ+ ⋯NCH) bonds formed between the benzene radical cation and HCN molecules (9 kcal/mol) indicating that the CH δ+ centers in the pyridine and pyrimidine radical cations have more effective charges than in the benzene radical cation.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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