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  • 1
    Electronic Resource
    Electronic Resource
    The ab initio calculated dipole moment surface and overtone relative intensities of CH chromophore in CHCl3 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 7484-7489 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Relative absorption intensities of the Fermi resonance polyads of isolated CH chromophore for the CHCl3 molecule were calculated with one-dimensional and two-dimensional dipole moment surfaces, which are obtained by the ab initio density functional method. The calculation showed an unusual strong absorption at the second Fermi resonance polyad, which agrees well with the experimental data. Such an intensities anomaly can be attributed to the nonlinearity of the dipole moment surface in the vicinity of the equilibrium configuration. By taking advantage of the two-dimensional dipole moment surface where both CH stretching and bending vibrations are taken into consideration, the ν1 and 2ν4 bands which constitute the first Fermi resonance polyad and have little wave function mixture, are found to be of almost equal intensity. Such a calculation agrees with observations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481346
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  • 2
    Electronic Resource
    Electronic Resource
    Band strengths for C–H stretching polyads of CHBr3 calculated by use of a two-dimensional electric dipole moment surface from density functional theory (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 8905-8912 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Band strengths of the Fermi resonance polyads involving C–H stretching and bending vibrations for the CHBr3 molecule are calculated with a one-dimensional dipole function and a two-dimensional dipole surface. These are obtained by the ab initio density functional method. Both treatments reproduce the interpolyad band strengths quite well, while the two-dimensional dipole moment surface is superior to the one-dimensional one in modeling the intrapolyad band strength pattern, indicating the importance of the bending vibrations in dipole moment surface and intensities calculations. The different behavior of interpolyad band strengths of CHBr3 compared to CHCl3, with an intensity anomaly occurring in the latter case, is illustrated by "dipole–weighted" overlap integrals. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1369660
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  • 3
    Electronic Resource
    Electronic Resource
    Calculation of the Si–H stretching–bending overtones in SiHCl3 employing ab initio potential energy and dipole moment surfaces (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 105-111 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Si–H stretching–bending overtones in SiHCl3 were investigated employing theoretically calculated potential energy surfaces (PES) and dipole moment surfaces (DMS). The coupled cluster method CCSD(T) was utilized to generate both one-dimensional (1D) and three-dimensional (3D) surfaces. An empirical 3D PES was also taken into consideration. The computed energy levels and band intensities agree reasonably well with observation for most of the bands. Comparison of CCSD(T) and density functional results for the very weak 2ν1 band shows that it is essential to calculate the DMS at a high level of quantum-chemical theory when cancellation of linear and quadratic contributions to the DMS is significant. The 3D ab initio PES yields more accurate band intensities than the empirical PES and therefore appears to be more realistic.© 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1417505
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  • 4
    Electronic Resource
    Electronic Resource
    The stretching vibrational overtone spectra of PH3: Local mode vibrational analysis, dipole moment surfaces from density functional theory and band intensities (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 7018-7026 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The infrared spectra of PH3 molecule were recorded on a Bruker IFS 120HR Fourier transform spectrometer from 4000 to 9500 cm−1. The P–H stretching vibrational frequencies and intensities were derived from the experimental data. The Morse oscillator parameters De and α in the anharmonically coupled anharmonic oscillator local mode model were determined by the least-squares fitting with the observed vibrational band centers. The ab initio three-dimensional P–H stretching dipole moment surfaces were calculated by the density functional theory method. The dipole moment vectors were projected to three kinds of molecule-fixed reference systems. The corresponding dipole moment components were fitted to polynomial functions in terms of the P–H bond length displacements with the molecular symmetry taken into account. The absolute band intensities were obtained and then compared with the experimental data. The results showed that a proposed improved bond dipole model can predict the absolute band intensities within a factor of 2 for most of the observed transitions, indicating a reasonably good agreement. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352038
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