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  • 11
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6655-6657 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By measuring the reduction of a spectral hole burnt at 500 mK due to temperature cycling experiments, we show that the lower bound of the distribution function of barrier heights is below 10 cm−1.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3134-3136 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We compare the spectral diffusion broadening of mesoporphyrin substituted horseradish peroxidase with the chromophore doped host glass. Whereas the broadening in the glass is smooth and follows a power law with an exponent close to (3)/(2) , there is a a steplike broadening in the protein which occurs around 14 K. The observed phenomena are interpreted on the basis of a two domain interaction of the chromophore with its environment.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7619-7624 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We applied hydrostatic pressure to spectral holes burned into a resorufin doped ethanol/methanol glass. We found that the line shift is perfectly linear with pressure and showed a pronounced dependence on the burn frequency as predicted by theory [J. Chem. Phys. 90, 3274 (1989)]. We exploited the burn frequency dependence to determine the solvent shift of the dye probe and the compressibility of the alcohol glass used. On the other hand, the behavior of the hole width under pressure shows features not predicted by theory: The broadening is, like the line shift, dependent on the burn frequency within the inhomogeneous band, yet in a nonlinear fashion. We attribute the color effect in the pressure induced broadening of the hole to a breakdown of the Gaussian approximation.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7296-7299 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show by temperature-cycling-hole-burning experiments that the conformational barriers of one-dimensional long chain aggregates of pseudoisocyanine iodide in frozen solutions follow a distribution of the form Pv(V)∼1/V . This is the same distribution as has been measured for three-dimensional glasses.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 871-874 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Highly frequency selective photochemistry at cryogenic temperatures is used to gain information on the excited state dynamics of large biomolecular aggregates, the phycobilisomes from the blue–green alga (cyanobacterium) Masticogladus laminosus. In particular, we show that in spite of the well organized structure of these aggregates disorder on a microscopic level dominates the optical spectra. The hole burning reaction in the resonantly excited chromophores is most probably due to a conformational change in the neighborhood of the chromophore. From the widths of the holes energy transfer times between different pigments on the order of 16 ps are determined. These transfer times are independent of the excitation energy.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 2935-2938 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigated the optical anisotropy and the normalized areas of persistent spectral holes in organic glasses over almost 1 week (4 decades). The systems studied were 1,4-dihydroxyanthraquinone and tetracene in an EtOH/MeOH glass. The areas of the holes decay on a logarithmic time scale, but the anisotropy remains constant. We draw the following conclusions: (i) There is no reorientation of dye molecules in the glass. (ii) Molecules relaxing from the product state reassume the position in the frequency domain and in space which they had before hole burning. (iii) A dye molecule seems to be strongly coupled just to one two level system (TLS).
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 3045-3050 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The low temperature conformational dynamics of the heme type protein mesoporphyrin-IX-substituted horseradish peroxidase is investigated by spectral diffusion waiting time/aging experiments. Spectral diffusion broadening is governed by a power law in time. There is a small but significant aging effect. It is assumed that the conformational dynamics of the protein which leads to the spectral broadening of the burnt-in holes is governed by a diffusion type equation. In this case the shape of the spectral diffusion kernel is Gaussian. This model is contrasted with spectral diffusion phenomena as described by the TLS-model (TLS, two level system). © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 8718-8721 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We compare the spectral diffusion dynamics of resorufin doped glycerol/H2O- and glycerol/D2O-glass with the respective dynamics of a chromoprotein in the same glass at 4.2 K. Spectral diffusion broadening of photochemical holes is measured over almost four orders of magnitude in time. In all samples there are strong aging phenomena. Resorufin in deuterated water/glycerol is reasonably well-described by the two level system (TLS) model. In the protonated glass, the TLS model does not seem to describe the experiments reasonably well. In the protein sample it totally fails. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 9638-9644 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The spectral diffusion dynamics was measured over 3 orders of magnitude in time of a myoglobin-type protein with the heme group substituted by Zn-pheophorbid a. After burning a photochemical hole at 4.2 K, the width of the spectral diffusion kernel is well described by a power law in waiting time with an exponent of 0.24. Spectral diffusion broadening is subject to "aging," viz., to the equilibration time at 4.2 K before hole burning. It decays with a power law in aging time. Deuteration of the solvent has a significant effect on the dynamics of the protein. Spectral diffusion broadening is smaller in the deuterated sample, however, the respective power law is not changed. The aging dynamics, on the other hand, does not seem to be influenced significantly by deuteration. The conclusion is that deuteration influences the fluctuations but not the relaxation. In addition to spectral diffusion, we also measured the recovery dynamics of the hole. It is slowed down tremendously by deuteration, confirming that the photoreaction is based on a light-induced proton transfer. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 10 (2000), S. 366-384 
    ISSN: 0961-5539
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Being extensively used in metallurgy, rotating magnetic fields are also becoming increasingly interesting for application in crystal growth, where they are intended to act by stabilizing the melt flow. For this purpose, it is important to understand the basic interactions of the magnetically induced flow and other flow components like time-dependent buoyant convection. So a three-dimensional finite volume method was developed in order to numerically study the effect of a rotating magnetic field on convection in a cylindrical melt volume. The equations of mass, momentum, and heat transport are solved together with the potential equations describing the electromagnetic field. The numerical computation of the Lorenz force distribution is validated by comparison with an analytical solution. The effects of magnetic field parameters on the temperature distributions and the flow patterns in the considered configurations are analysed.
    Type of Medium: Electronic Resource
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