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DF: Dielektrische Festkörper
DF 3: Gl
äser I (gemeinsam FV DF/DY)
DF 3.4: Talk
Tuesday, March 9, 2004, 10:45–11:00, H23
Dielectric relaxation in binary organic glass formers: β process vs. HF-wing scenario and heterogeneous dynamics — •Thomas Blochowicz and Ernst Rössler — Universität Bayreuth
We study a series of binary mixtures using 2-picoline in oligomeric styrenes, in particular tri-styrene. The binary mixtures were characterised by broad band dielectric spectroscopy in the dynamic range 10−6−107 Hz. Although neither of the substances shows a secondary relaxation peak in the neat phase, there appears a strong β-process in the spectra of the picoline molecules in the mixture. In fact a careful lineshape analysis of χ″(ω) with a set of appropriate model functions shows that the same process that is seen as a high frequency wing at high picoline concentrations becomes a β relaxation at lower concentrations due to a separation of time scales. Moreover, in the intermediate concentration range a strong broadening of the spectra as compared to neat picoline is observed. Non-resonant dielectric hole burning reveals that this broadening is on the one hand due to pronounced, long-lived dynamic heterogeneities but to some part also due to intrinsically non-exponential relaxation.