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  • 1
    Electronic Resource
    Electronic Resource
    Calculating rovibrational energy levels of a triatomic molecule with a simple Lanczos method (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 10269-10274 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a simple Lanczos method for calculating rovibrational energy levels of a triatomic molecule from a kinetic energy operator (KEO) with the z axis perpendicular to the molecular plane. We use rotational basis functions which are linear combinations of symmetric top functions so that all matrix elements are real. For some molecules, coupling between rotation and vibration is less important if the z axis is chosen perpendicular to the molecular plane, but the singularities of the z-axis operator are more difficult to deal with than those of the commonly used y-axis operator. The KEO with z axis perpendicular to the plane also reduces the number of sums over vibrational indices required to evaluate Hamiltonian matrix-vector products. Using a new symmetry-adapted basis and the z-axis KEO we calculate rovibrational energy levels of H2O for high J values. Even at J=40 we do not observe the formation of fourfold clusters. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478960
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  • 2
    Electronic Resource
    Electronic Resource
    Calculation of vibrational (J=0) excitation energies and band intensities of formaldehyde using the recursive residue generation method (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 7807-7820 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We use the recursive residue generation method (RRGM) with an exact kinetic energy operator to calculate vibrational excitation energies and band intensities for formaldehyde. The basis is a product of one-dimensional potential optimized discrete variable representation (PO-DVR) functions for each coordinate. We exploit the symmetry by using symmetry adapted basis functions obtained by taking linear combinations of PO-DVR functions. Our largest basis set consists of 798 600 functions (per symmetry block). The Lanczos tridiagonal representation of the Hamiltonian is generated iteratively (without constructing matrix elements explicitly) by sequential transformations. We determine a six-dimensional dipole moment function from the ab initio dipole moment values computed at the QCISD level with a 6-311++G(d,p) basis set. We converged all A1, B2 and B1 vibrational states up to the combination band with two quanta in the C–O stretch and one quantum in a C–H stretch at about 6 350 cm−1 above zero point energy. We present a simulated (J=0) infrared spectrum of CH2O for transitions from the ground state. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471529
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    Paper (German National Licenses)
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