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Browsing by Author "Niu, Y. L."

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    Quantum chemical calculation of intramolecular vibrational redistribution and vibrational energy transfer of water clusters
    (2013-10-24)
    Niu, Y. L.
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    Pang, R.
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    Zhu, C. Y.
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    Hayashi, M.
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    Fujimura, Y.
    In present letter the adiabatic approximation is applied to the intramolecular vibrational redistribution (IVR) of water clusters. The isotope, blocking and cluster-size effects are investigated. This letter also examines the assumption associated with the transition state theory applied to unimolecular reactions; that is, IVR is assumed to be completed before the reaction takes place. For this purpose, we choose to study (H2O)(2)H+ -> H2O+ H3O+, and (H2O)(2) -> 2H(2)O processes. In molecular clusters, the vibrational excitation energy transfer between different normal modes has been observed. This will also be investigated for the deuterated species of (HOD)(2)H+. (C) 2013 Elsevier B.V. All rights reserved.
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    Quantum-mechanical approach to predissociation of water dimers in the vibrational adiabatic representation: Importance of channel interactions
    (2015-08-28)
    Mineo, H.
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    Niu, Y. L.
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    Kuo, J. L.
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    Lin, S. H.
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    Fujimura, Y.
    The results of application of the quantum-mechanical adiabatic theory to vibrational predissociation (VPD) of water dimers, (H2O)(2) and (D2O)(2), are presented. We consider the VPD processes including the totally symmetric OH mode of the dimer and the bending mode of the fragment. The VPD in the adiabatic representation is induced by breakdown of the vibrational adiabatic approximation, and two types of nonadiabatic coupling matrix elements are involved: one provides the VPD induced by the low-frequency dissociation mode and the other provides the VPD through channel interactions induced by the low-frequency modes. The VPD rate constants were calculated using the Fermi golden rule expression. A closed form for the nonadiabatic transition matrix element between the discrete and continuum states was derived in the Morse potential model. All of the parameters used were obtained from the potential surfaces of the water dimers, which were calculated by the density functional theory procedures. The VPD rate constants for the two processes were calculated in the non-Condon scheme beyond the so-called Condon approximation. The channel interactions in and between the initial and final states were taken into account, and those are found to increase the VPD rates by 3(1) orders of magnitude for the VPD processes in (H2O)(2) ((D2O)(2)). The fraction of the bending-excited donor fragments is larger than that of the bending-excited acceptor fragments. The results obtained by quantum-mechanical approach are compared with both experimental and quasi-classical trajectory calculation results. (C) 2015 AIP Publishing LLC.
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