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  • Computational Chemistry and Molecular Modeling  (1)
  • Relaxation times  (1)
  • Stripping analysis  (1)
  • 1
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 783-791 
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the framework of the SCF-RPA scheme and ppp approximation we studied the excitation spectrum of pyrene, coronene, ovalene, and hexabenzocoronene. The triplet stability matrix of the corresponding Hartree-Fock solution was also studied for each molecule. At variance with the case of long linear polyacenes [M. Baldo, G. Piccitto, R. Pucci, and P. Tomasello, Phys. Lett. 95A, 201 (1983)], all these molecules do not display Hartree-Fock triplet instability. Furthermore, the theoretical analysis indicates that the electronic structure of the molecular series can be characterized by a dimensionality intermediate between one and two, with a smooth transition between the two limits. The transition is essentially determined by the molecular shape. The analysis is supported by the fairly good agreement of the theoretical spectra with the available experimental data.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1040-0397
    Schlagwort(e): Microelectrodes ; Stripping analysis ; Mercury ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The performance of spherically shaped mercury microelectrodes, formed by electroreduction of mercury onto an inlaid platinum microdisk of radius r, characterized by different deposit heights, h, have been investigated for cyclic (CV) and anodic stripping (ASV) voltammetry. Electrodes with h/r ratio in the range 0.1-2 have been tested in solutions containing Pb2+ and Cd2+ in NaCl and NaClO4 + HClO4 as supporting electrolytes. For cyclic vodtammetry the results obtained indicated that the width at half height (w1/2), the peak current (ip) and the charge of the anodic stripping peak (Qs) depend on the h/r parameter. Particular attention has been devoted to the relation between the charge of the cathodic process and the anodic charge of the stripping peaks. It has been found that the experimental charge values involved in the cathodic and anodic scan agree within 3%, irrespective of the mercury thickness, indicating a complete stripping of the metals deposited in the mercury. For ASV the Pt-Cd intermetallic compounds have been found to influence the stripping peak of cadmium for electrodes with h/r ≤ 1 and for concentrations of Cd2+ lower than 10-6 M. By exploiting the known properties of the mercury microelectrodes in stripping analysis, an absolute method, based on the charge associated with the stripping peak, has been applied for determining the labile fraction of the above cations in a pore-water sample of the Venice lagoon.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 533-539 
    ISSN: 0749-1581
    Schlagwort(e): Relaxation times ; Angular correlation function ; Diffusion equation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The motion of a flexible molecule in solution can be described as a Brownian motion between the different conformations that the molecule can assume. Each conformation corresponds to a local minimum of the energy surface. A simple model is given for this type of motion in relation to nuclear magnetic resonance (NMR) relaxation measurements. This is based only on the assumption that the diffusion tensor for the overall tumbling is not appreciably affected by jumping between the different conformations. The limits of the model are discussed and an illustrative application to 2-fluorobutane is given.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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