Search Results - (Author, Cooperation:I. Burghardt)

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  1. 1
    Staff View
    Publication Date:
    2015-09-12
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Burghardt, I. ; Gaspard, P.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The dynamics of the molecular transition state, in a reaction or photodissociation process, may be analyzed by semiclassical methods. We investigate the classical dynamics of the transition state in the dissociation HgI2 (X 1Σ+g)→hνHgI(X 2Σ+)+I, and apply the semiclassical quantization methods based on periodic-orbit theory. A series of resonances is characterized in a low-energy regime, where the classical dynamics is regular, and at high energies, after a transition to chaos has occurred. In a complementary fashion, we analyze the quantum-mechanical propagation of wave packets. The spectrum which is derived from the quantum-mechanical autocorrelation function is compared with the semiclassical results.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.467049

    Articles: DFG German National Licenses
  3. 3
    Burghardt, I.

    College Park, Md. : American Institute of Physics (AIP)
    Published 2001
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    Dynamical equations for a subsystem interacting with an environment are proposed which are adapted to a multiconfigurational form of the density operator. Initial correlations are accounted for in a non-Markovian master equation. Two variants of the latter are derived by projection operator techniques and cumulant expansion techniques, respectively. The present scheme is developed in view of describing the ultrafast dynamics in solute–solvent complexes where the details of system–environment correlations are of importance. The master equation is readily integrated into the equations of motion derived by the multiconfiguration time-dependent Hartree method, which provides an efficient scheme for the numerical propagation of the density operator. © 2001 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1329648

    Articles: DFG German National Licenses
  4. 4
    Burghardt, I.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1999
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    A consistent treatment of environmental effects is proposed in the framework of the multiconfiguration time-dependent Hartree (MCTDH) method. The method is extended in view of treating complex molecular systems which require an exact quantum dynamics for a certain number of "primary" modes while an approximate dynamics is adequate for a class of "secondary" modes. The latter may correspond to the weakly coupled modes in a polyatomic molecule, or the first solvent shell in a solute-solvent complex. For these modes, a description in terms of parameterized functions is introduced. The MCTDH working equations are generalized to allow for the nonorthogonality of these functions, which may take, e.g., a multidimensional Gaussian form. The formalism is developed on the level of both the wave function description and the density matrix description. Dissipative effects are accounted for in terms of a stochastic Hamiltonian approach versus master equation approach in the respective descriptions. © 1999 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.479574

    Articles: DFG German National Licenses
  5. 5
    Raab, A. ; Burghardt, I. ; Meyer, H.-D.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1999
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The multiconfiguration time-dependent Hartree (MCTDH) method is formulated for density operators and applied to their numerical propagation. We introduce two types of MCTDH density operators which are expanded in different kinds of so-called single-particle density operators. The latter may either be hermitian, or else represent ket–bra products of so-called single-particle functions. For both types of MCTDH expansions of density operators we derive equations of motion employing the Dirac–Frenkel/MacLachlan variational principle. Further an alternative set of equations of motion for the second type of density operators is proposed, which is not based on a variational principle but derived by taking partial traces. We thus obtain three sensible approaches within the framework of the MCTDH method which differ in their performance and properties. We investigate these approaches and their properties analytically and numerically. Our numerical results refer to a model of vibronic-coupling dynamics in the pyrazine molecule representing coupled electronic states with four vibrational modes and two and three electronic states respectively. We analyze the closed-system dynamics for this model with temperature-dependent initial states. The influence of temperature on state populations, on correlation functions and on absorption spectra is discussed. We assess the numerical performance of two of the three approaches and find that both can be very efficiently applied to investigate the type of systems studied here. © 1999 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.480334

    Articles: DFG German National Licenses
  6. 6
    Burghardt, I.

    College Park, Md. : American Institute of Physics (AIP)
    Published 2001
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    Quantum-mechanical hydrodynamic equations are considered for mixed quantum states, and the corresponding equations for pure quantum states are derived as a particular case. A generalization of the "quantum potential" of Bohmian mechanics is formulated. In the mixed-state case, an infinite hierarchy of kinetic equations arises that may be truncated by introducing suitable approximations. The influence of dissipation on the kinetic equations is discussed. © 2001 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1416493

    Articles: DFG German National Licenses
  7. 7
    Burghardt, I.

    College Park, Md. : American Institute of Physics (AIP)
    Published 2001
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    A hydrodynamic approach is developed to describe nonadiabatic nuclear dynamics. We derive a hierarchy of hydrodynamic equations which are equivalent to the exact quantum Liouville equation for coupled electronic states. It is shown how the interplay between electronic populations and coherences translates into the coupled dynamics of the corresponding hydrodynamic fields. For the particular case of pure quantum states, the hydrodynamic hierarchy terminates such that the dynamics may be described in terms of the local densities and momentum fields associated with each of the electronic states. © 2001 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1416494

    Articles: DFG German National Licenses
  8. 8
    Bohlen, J.-M. ; Burghardt, I. ; Rey, M. ; Bodenhausen, G.

    Amsterdam : Elsevier
    Staff View
    ISSN:
    0022-2364
    Source:
    Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics:
    Physics
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1016/0022-2364(90)90377-L

    Articles: DFG German National Licenses
  9. 9
    Emsley, L. ; Burghardt, I. ; Bodenhausen, G.

    Amsterdam : Elsevier
    Staff View
    ISSN:
    0022-2364
    Source:
    Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics:
    Physics
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1016/0022-2364(90)90381-I

    Articles: DFG German National Licenses
  10. 10
    Emsley, L. ; Burghardt, I. ; Bodenhausen, G.

    Amsterdam : Elsevier
    Staff View
    ISSN:
    0022-2364
    Source:
    Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics:
    Physics
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1016/0022-2364(91)90130-L

    Articles: DFG German National Licenses
  11. 11
    Staff View
    ISSN:
    0022-2364
    Source:
    Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics:
    Physics
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1016/0022-2364(90)90044-A

    Articles: DFG German National Licenses