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  • American Institute of Physics (AIP)  (5)
  • 1
    Electronic Resource
    Electronic Resource
    The effect of charged impurities on a glass transition in a polar medium (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 664-668 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A phase transition from a liquid to glass state is studied for polar solvents in the presence of ions. The entropy and free energy of the system above and below the transition temperature, Tc, is found on the basis of the theory of random dipole–dipole and charge–dipole interactions . The dependence of the transition temperature on the concentration of charged impurities, c, is found. It is shown that a relative charge concentration of only 10−5 is needed to increase Tc by 20 K. The transition temperature is also dependent on the value of the charge. For a Fe+3/Fe+2 reactive complex the transition temperature is changed by 10 K for c=10−6. For dissolved salts we describe the relationship between Tc and the separation distance of the ion pair. The glass transition is insensitive to the size of dissolved ions. The theory proposed has only one adjustable parameter, the elementary dipole moment of the solvent. The theory allows to explain a peak dependence in Tc measured as a function of the alcohol content Y in Li+Cl−⋅5H2O⋅Y alcohol(methanol, ethanol, 1-propanol) mixtures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470862
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  • 2
    Electronic Resource
    Electronic Resource
    Multiphoton absorption by metal–metal long distance charge-transfer complexes in polar solvents (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9441-9453 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theory of multiphoton absorption of mixed valence compounds in polar solvents is developed. When these systems interact with a strong laser field, there exist various absorption "channels'' which correspond to one, two, three,..., absorbed photon quanta. The probability of each channel to be switched on or off is dependent on the laser intensity, which results in strong intensity dependence of the absorption spectrum. Bands can be eliminated from the spectrum simply by changing the laser intensity. The physical picture of channels is justified by a derivation based on a kinetic master equation for the flow of electronic population. Calculations are carried out for the case where the polar environment can be modeled by a single high frequency ("quantum'') vibrational mode plus a classical bath represented by a collection of low frequency harmonic oscillators. The spectrum is found to be only weakly sensitive to the quantum vibrational mode. Suggestions for experimental verification are made. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472778
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  • 3
    Electronic Resource
    Electronic Resource
    "False tunneling'' and multirelaxation time nonexponential kinetics of electron transfer in polar glasses (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 1875-1885 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Classical electron transfer in polar glasses is described by a theory based on a model microscopic Hamiltonian which includes the discreteness and randomness of the glassy polar modes with distinct orientation. When configurational dynamics is fast, the reaction is described by exponential kinetics with a rate constant of non-Arrhenius type. The temperature dependent rate constant resembles the tunneling rate, despite the classical transfer of the electron. This effect is called "false tunneling.'' In this limit the possibility of a self-acceleration of the reaction is pointed out. When configurational dynamics is very slow the reaction kinetics are nonexponential with multirelaxation time behavior. The reaction is shown to be almost insensitive to temperature change pointing out on a possible explanation of a broad temperature-independent range in the "rate constant'' in an electron transfer in cytochrome c oxidation in chromatium. At short times, the reaction accelerates compared to the exponential behavior, while at long times it becomes slower. For strongly exothermic reactions the kinetics are always slower than an exponential decay. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470943
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  • 4
    Electronic Resource
    Electronic Resource
    Response to "Comment on ‘The effect of charged impurities on a glass transition in a polar medium' '' [J. Chem. Phys. 105, 8979 (1996)] (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 8981-8982 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The theory presented in [J. Chem. Phys. 104, 669 (1996)] deals with the effect of separated charged impurities on the glass transition temperature Tg. To explain experimental data on the effect of salt on the glass transition temperature, it is necessary to include mechanisms of aggregation and dissociation of salt molecules. Due to aggregation and dissociation, the concentration of charges can be different than the salt concentration. It is pointed out that this might explain the discrepancy between some experimental data and the theory. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472629
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  • 5
    Electronic Resource
    Electronic Resource
    Long-range electron transfer driven by two lasers: Induced irradiance (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 691-703 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Kinetics and nonlinear optical properties of a long range electron transfer complex in a polar solvent are studied in the presence of two perpendicularly directed, independent (incoherent) lasers with electric fields aligned along the electron path. The rate constant and absorption/emission cross sections in both direction are computed on the basis of the channel approach, whose validity is justified by a rigorous derivation. It is found that despite strong dissipation due to interaction with the polar environment, emission can be stimulated in one ("primary") direction. The emission spectra are found to depend on the frequency of the auxiliary laser propagating perpendicular to the direction of the primary laser, the intensities of both lasers, the frequency and reorganization energy of quantum modes in the solvent, and the reaction heat. The emission spectrum is only slightly sensitive to the laser intensities in certain high frequency regimes. The latter property is important for potential applications in which the reaction system would be employed as the working system for a laser with tunable frequency. Calculations suggest that a long range electron transfer system can be also used as a nonlinear optical device which transfers energy from one laser to another. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476608
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