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  • 1
    Electronic Resource
    Electronic Resource
    Nonadiabatic donor–acceptor electron transfer mediated by a molecular bridge: A unified theoretical description of the superexchange and hopping mechanism (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 7107-7122 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nonadiabatic bridge-assisted electron transfer (ET) is described by a set of kinetic equations which simultaneously account for the sequential (hopping) as well as the superexchange mechanism. The analysis is based on the introduction of a certain reduced density operator describing a particular set of electron-vibrational levels of the molecular units (sites) involved in the transfer act. For the limiting case of intrasite relaxations proceeding fast compared to intersite transitions a set of rate equations is obtained. This set describes the time evolution of the electronic site populations and is valid for bridges with an arbitrary number of units. If the rate constants for the transition from the bridge to the donor as well as to the acceptor exceed those for the reverse transitions the ET reduces to a single-exponential process with an effective forward and backward transfer rate. These effective rates contain a contribution from the sequential and a contribution from the superexchange mechanisms. A detailed analysis of both mechanisms is given showing their temperature dependence, their dependence on the number of bridge units, and the influence of the energy gap and the driving force. It is demonstrated that for integral bridge populations less than 10−3 the complicated bridge-mediated ET reduces to a donor–acceptor ET with an effective overall transfer rate. This transfer rate contains contributions from the sequential as well as the superexchange mechanisms, and thus can be used for a quantitative analysis of the efficiency of different electron pathways. For room-temperature conditions and even at a very small bridge population of 10−4–10−10 the superexchange mechanism is superimposed by the sequential one if the number of bridge units exceeds 4 or 5. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1404389
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  • 2
    Electronic Resource
    Electronic Resource
    Bridge-assisted electron transfer driven by dichotomically fluctuating tunneling coupling (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 4937-4944 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The influence of dichotomically fluctuating tunneling coupling on long-range electron transfer is studied theoretically. Within an approach similar to the noninteracting blip approximation known from the spin-boson model a set of coupled integrodifferential kinetic equations is derived. These equations describe the time development of the electronic populations difference between the donor and acceptor states averaged with respect to the stochastic process and the quantum fluctuations of the bath. Furthermore, they contain the correlator between the level population difference and the fluctuating tunneling matrix element. A detailed analysis is carried out for the case of a strong coupling of the transferred electron to a single soft reaction coordinate. Within a Markovian approximation and an adiabatic removing of the correlator, the balance type kinetic equations can be derived which contain effective transfer rates. These rates depend strongly on the correlation time of fluctuations and can exhibit a resonancelike behavior. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470630
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic field control of an electron tunnel current through a molecular wire (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4386-4396 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The influence of an external magnetic field on the elastic interelectrode tunneling mediated by a molecular wire is studied theoretically for the case in which the wire contains paramagnetic ions. A spin-filtration effect for incoming electrons and a spin-polarization effect for outgoing electrons can be demonstrated for a wire including a single paramagnetic ion as well as a pair of identical antiferromagnetically coupled ions. It is assumed that each paramagnetic ion reduces its spin in the electronic ground-state from S to S−1/2 if the transferred electron forms an intermediate bound state with the ion. Just such a spin reduction results in a transfer which is spin forbidden for spin-down electrons along the predominant tunneling channels. These channels are characterized by the lowest possible spin-projections of the paramagnetic ions. The spin reduction also determines the magnetic field dependence of the transfer rate in a specific manner. In the case of two paramagnetic ions the combined action of the magnetic field and the exchange interaction between the ions is responsible for a step-like dependence of the tunnel current on the magnetic field. The exact dependence of the interelectrode current on the magnetic field-strength at a low temperature is derived in using Wigner's 6j-symbols methods. The specific spin-polarization effect observed earlier in metal–ferromagnetic insulator–vacuum experiments on electron tunneling is explained in the framework of a spin-filtration effect at which the predominant tunneling channels are responsible for a tunnel interelectrode current. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475851
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  • 4
    Electronic Resource
    Electronic Resource
    Control of long-range electron transfer in dynamically disordered molecular systems by an external periodic field (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 4522-4530 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The influence of a strong periodic field on the long-range electron transfer is studied theoretically within the driven spin-boson model extended by a dichotomically fluctuating tunneling coupling. Applying the noninteracting blip approximation, a set of coupled kinetic equations is derived. It describes the time-development of the electronic population difference between the donor and acceptor states averaged with respect to the stochastic process, the quantum fluctuations of the bath and over the fast oscillating field. The strength of the periodic field is taken into account in a nonperturbative manner. A detailed analysis is carried out for the case of a strong coupling of the transferred electron to a specific reaction coordinate. Analytical expressions for the effective transfer rate are obtained and their numerical analysis is presented. For the case of adiabatically controlled (gated) transfer the existence of a transfer regime is demonstrated where the strong external field does not influence the effective transfer rate, however, it can completely revert the direction of the transfer. Finally, it is shown that the periodic field can induce transitions between the quasi-adiabatic (gated) and the nonadiabatic regime of electron transfer. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473495
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  • 5
    Electronic Resource
    Electronic Resource
    The magnetic-field influence on the inelastic electron tunnel current mediated by a molecular wire (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9561-9573 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnetic-field influence on the inelastic interelectrode tunnel current mediated by a molecular wire is studied theoretically for the case in which the wire includes paramagnetic ions with frozen angular momenta. The vibrational and spin relaxation within the terminal sites of the wire (adjacent to the electrodes) are assumed to be much faster than the related jump of the tunneling electron. For a wire containing a pair of paramagnetic ions, a low-temperature blocking of the current is demonstrated for the cases of ions both coupled by an exchange interaction and largely separated in space. The blocking is shown to appear if the paramagnetic ion reduces its electronic ground-state spin S to S−〈fraction SHAPE="CASE"〉12 during the formation of the intermediate bound state with the transferred electron. At low temperatures the current formation is predominantly originated thus by tunnel channels for which the magnetic energy of paramagnetic ions has a minimal value. In the presence of an exchange spin–spin interaction or a single-ion anisotropy, just these predominant channels are manifested to form a steplike behavior of the current before the current itself is completely blocked by the increasing magnetic field. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477618
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetics of donor-acceptor transition with allowance for vibrational structure (1979)
    Springer
    Theoretical and mathematical physics 38 (1979), S. 264-269 
    Details
    ISSN: 1573-9333
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01018546
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of relaxation transitions between multilevel quantum states (1981)
    Springer
    Theoretical and mathematical physics 49 (1981), S. 928-933 
    Details
    ISSN: 1573-9333
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01019126
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic equations for a quantum dynamical system interacting with a thermal reservoir and a random field (1990)
    Springer
    Theoretical and mathematical physics 84 (1990), S. 986-995 
    Details
    ISSN: 1573-9333
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01017358
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetic equations for quantum subsystems with finite number of degrees of freedom in a condensed medium (1981)
    Springer
    Theoretical and mathematical physics 46 (1981), S. 65-73 
    Details
    ISSN: 1573-9333
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01019451
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  • 10
    Electronic Resource
    Electronic Resource
    Theory of band and bound states of double triplet excitations in molecular crystals. I (1971)
    Springer
    Theoretical and mathematical physics 6 (1971), S. 313-321 
    Details
    ISSN: 1573-9333
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01030113
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