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  • 1
    Electronic Resource
    Electronic Resource
    Construction scheme for regularized diabatic states (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 2377-2388 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple construction scheme for quasidiabatic electronic states implemented earlier for a Jahn–Teller situation [J. Chem. Phys. 110, 9371 (1999)] is extended to the case of a seam of symmetry-allowed conical intersections. It is based on the idea of removing only the singular part of the nonadiabatic coupling elements, leading to the notion of "regularized" diabatic states. Explicit working equations are given for the resulting potential energy matrix which require only information from the adiabatic potential energy surfaces alone. The approach is tested for the photodissociation of H2S and O3 and very good agreement with reference data from the literature is found. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383986
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  • 2
    Electronic Resource
    Electronic Resource
    Multistate vibronic interactions in the benzene radical cation. II. Quantum dynamical simulations (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 2657-2671 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The multistate vibronic dynamics in the X˜ 2E1g-E˜ 2B2u electronic states of the benzene radical cation is investigated theoretically by an ab initio quantum-dynamical approach. The vibronic coupling scheme and the ab initio values of the system parameters are adopted from the previous Paper I. Vibronic line spectra are obtained with the Lanczos procedure. Extensive calculations on wave-packet propagation have been performed with the aid of the multiconfiguration time-dependent Hartree method. Up to five coupled electronic potential energy surfaces and 13 vibrational degrees of freedom have been included in these calculations. As a result, the impact of a third electronic state (X˜ or B˜) on a strongly coupled manifold (B˜-C˜ or D˜-E˜ states) is quantitatively assessed. It leads to a restructuring of the spectral envelope which is stronger for the B˜-D˜-E˜ than for the X˜-B˜-C˜ system. The internal conversion dynamics is characterized by a stepwise transfer of electronic population to the lowest electronic state on a time scale of ∼100 fs, if the system is prepared initially on the highest potential energy surface. Companion calculations have also been performed for the case when the system is prepared in the intermediate state at t=0; they show a branching of the electronic populations. These are all novel findings which are discussed in terms of a series of conical intersections between the various potential energy surfaces. The importance of such multistate vibronic interactions for the photophysics and photochemistry of medium-sized systems is pointed out. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491398
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  • 3
    Electronic Resource
    Electronic Resource
    Collective quantum tunneling of strongly correlated electrons in commensurate mesoscopic rings (2001)
    Springer
    The European physical journal 20 (2001), S. 289-299 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 71.45.Lr Charge-density-wave systems – 75.30.Fv Spin-density waves – 72.15.Nj Collective modes (e.g., in one-dimensional conductors – 73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present a new effect that is possible for strongly correlated electrons in commensurate mesoscopic rings: the collective tunneling of electrons between classically equivalent configurations, corresponding to ordered states possessing charge and spin density waves (CDW, SDW) and charge separation (CS). Within an extended Hubbard model at half filling studied by exact numerical diagonalization, we demonstrate that the ground state phase diagram comprises, besides conventional critical lines separating states characterized by different orderings (e.g. CDW, SDW, CS), critical lines separating phases with the same ordering (e.g. CDW-CDW) but with different symmetries. While the former also exist in infinite systems, the latter are specific for mesoscopic systems and directly related to a collective tunnel effect. We emphasize that, in order to construct correctly a phase diagram for mesoscopic rings, the examination of CDW, SDW and CS correlation functions alone is not sufficient, and one should also consider the symmetry of the wave function that cannot be broken. We present examples demonstrating that the jumps in relevant physical properties at the conventional and new critical lines are of comparable magnitude. These transitions could be studied experimentally e.g. by optical absorption in mesoscopic systems. Possible candidates are cyclic molecules and ring-like nanostructures of quantum dots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510170278
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