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  • 1
    Electronic Resource
    Electronic Resource
    Direct measurements of energy transfer between identical chromophores in solution (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7557-7562 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rate of intramolecular electronic excitation energy transfer in 9,9' bifluorene has been investigated in a variety of solvents, using both time-correlated single photon counting and femtosecond fluorescence upconversion technique. The kinetics of energy transfer were determined in both cases by time dependent fluorescence anisotropy measurements. The energy transfer dynamics between fluorene moieties has been found to occur on a time scale of approximately 600 fs in different solvents and has been correlated with the T2 value calculated from the absorption linewidth and the β value obtained from jet measurements. The dihedral angle between the fluorene moieties was also calculated from the anisotropy measurement and compared with the values obtained from a solution phase NMR determination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457279
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Vibrational and rotational relaxation times of solvated molecular ions (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 5499-5507 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Infrared pump–probe and infrared polarization spectroscopy have been used to measure the vibrational relaxation times (T1) of the antisymmetric stretching mode and the reorientation times (TR) for N3−, NCS−, and NCO− in D2O and/or methanol. For N3−, experiments were also conducted in H2O and hexamethyl–phosphamide (HPMA) solutions. The rapid vibrational relaxation and slow reorientation observed demonstrate strong coupling between the ions and the solvents. Longer vibrational relaxation and shorter reorientation times measured for NCS− reveal weaker solvent interactions that may be due to the importance of the charge distribution and the form of the normal coordinate. A comparison of the T1 and TR times in different solvents permits a determination of the relative interaction strengths for the solvents investigated. The relatively weaker coupling of N3− in the aprotic solvent HMPA demonstrates the importance of hydrogen bonding in strong solvent interactions in ionic solutions. The experimental results are compared with recent molecular dynamics simulations of ionic solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464899
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Femtosecond coherent transient infrared spectroscopy of CO on Cu(111) (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 4421-4427 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Femtosecond infrared coherent transients have been measured for the stretch vibration of CO on Cu(111). The free induction decay exhibits a dephasing time (T2) of 2±0.3 ps (and 2±0.1 ps assuming a single exponential decay between 2 and 3 ps). The decay was best fit by exponential relaxation, thereby suggesting that the CO vibrational band is almost entirely homogeneously broadened. The surface sum frequency spectrum was also measured at two coverages (0.10 and 0.45 L) using spectrally narrowed pulses. Interferences were observed leading to a determination of the relative phase and amplitude of the resonant and nonresonant second-order susceptibility in this system. The magnitude of the nonresonant susceptibility was only weakly dependent on coverage, suggesting that the nonresonant polarizability originates in the bulk Cu. Time and frequency domain results were in good agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463884
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    Paper (German National Licenses)
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