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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1830-1835 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dependence of frequency, width, and area of spectral holes on pressure were measured at 1.6 K in the pressure range up to 2.5 MPa for dimethyl-s-tetrazine (DMST) doped n-hexane (Shpol'skii system), and as reference systems, for DMST-doped durene ("hard" molecular crystal) and ethanol:methanol glass. For the Shpol'skii system, in addition the inhomogenous fluorescence spectra were measured for normal and high (200 MPa) pressures. The main observations were the following: (i) spectral holes in the Shpol'skii system exhibit very large pressure-induced broadening (up to 65 GHz/MPa) depending essentially on the prehistory (freezing pressure) and exceeding the corresponding values for durene (by far) and glass; (ii) spectral holes in the Shpol'skii system exhibit strong, and to a large extent, reversible, area reduction with applied pressure; and (iii) the inhomogeneous fluorescence lines show quite a moderate (as compared to holes) pressure broadening of about several GHz/MPa. The results for the Shpol'skii system are shown to be inconsistent with existing theories. They are qualitatively explained by pressure-induced dynamics of vacancy defects in the frozen n-alkanes. © 1998 American Institute of Physics. [S0021-9606(98)50504-1]
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6780-6790 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A joint analysis of spectroscopic data obtained at liquid–helium temperatures by three line-narrowing techniques, photon echo (PE), persistent hole burning (HB), and single molecule spectroscopy (SMS), is presented. Two polymer systems, polyisobutylene (PIB) and polymethylmethacrylate (PMMA), doped with tetra-tert-butylterrylene (TBT) were studied via PE and HB techniques and the results are compared with literature data [R. Kettner et al., J. Phys. Chem. 98, 6671 (1994); B. Kozankiewicz et al., J. Chem. Phys. 101, 9377 (1994)] obtained by SMS. Both systems behave quite differently. In TBT/PIB a rather strong influence of a dispersion of the dephasing time T2 was found which plays only a minor role in TBT/PMMA. We have also measured the temperature dependence of T2 for both systems in a broad temperature range (0.4–22 K). Using these data we separated the two different contributions to the optical dephasing — due to an interaction with two-level systems and due to coupling with local low-frequency modes. The data are compared with calculations using a numerical and a semianalytical model in the presence of a large dispersion of the single molecule parameters. Furthermore, we discuss the differences of the linewidths as measured by different experimental methods. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have measured the 16 Hz susceptibility of the diluted Van Vleck paramagnets Pr1−x Y x Ni5 withx=0.00, 0.05, 0.10. 0.20 at temperatures 1.5 K≤T≤50 K and magnetic fields up to 15T. Their Van Vleck type magnetic susceptibility χ(T, B, x) strongly depends on the field atB≥6 T. The temperatureT max(B, x) of the maximum of χ(T, B, x) decreases at increasing the field from zero to 15 T by approximately one order of magnitude for all Pr1−x Y x Ni5 compounds. Changing the dilutionx from zero to 0.20, the field whereT max(B, x) strongly drops is increased from 9 T to 11 T. Our data agree qualitatively with the predictions of a point charge model which considers the Zeeman term in addition to the electronic exchange and the dominating crystal field contributions.
    Type of Medium: Electronic Resource
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