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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 4827-4835 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoisomerization of cis-stilbene in liquid solution was studied by time-resolved excited-state absorption spectroscopy using 306 nm pump and 612 nm probe pulses of 100 fs width. Transient absorption signals were found to decrease exponentially with time. Decay rate constants were determined over the pressure range 1–4000 bars at temperatures of 295 and 390 K in a series of alkane solvents as well as in methanol, acetonitrile, and in polymethylmethacrylate (PMMA). The viscosity dependence confirms the existence of two pathways of the reaction, one leading to ground-state cis- and trans-stilbene (C/TS), the other to dihydrophenanthrene (DHP). Whereas the DHP component shows only little viscosity dependence up to 4 kbar, the C/TS component is characterized by rate constants which are inversely proportional to the solvent viscosity. This is in contrast to earlier conclusions from studies with solvents at 1 bar. The C/TS process shows practically no temperature dependence apart from that of the viscosity, whereas the DHP process has an apparent activation energy of 8.5 kJ mol−1. The results are interpreted in terms of a Kramers–Smoluchowski equation for low-barrier processes as well as by solvent modifications of the low-barrier potential. Alternative interpretations by rate theory for barrierless processes are considered as well.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4393-4394 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new cell design for off-axis amplification of femtosecond dye lasers which uses total internal reflection is reported. Compared to the conventional on-axis configuration, these amplifiers produce less amplified spontaneous emission in the far field and maintain the input beam profile. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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