Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 11: Glasses I (joint session DF/DY)

DY 11.6: Vortrag

Dienstag, 26. Februar 2008, 11:00–11:15, EB 407

The high frequency wing of the α-process as probed by depolarized light scattering — •Nikolaus Petzold, Alexander Brodin, and E. A. Rössler — Universität Bayreuth

We show that the "intermediate power law" recently observed in optical Kerr effect (OKE) measurements is equivalent with the excess wing from frequency-domain data long since known from dielectric spectroscopy (DS), and is an equally common feature in depolarised light scattering (DLS). From the OKE representation we find that the wing from OKE and DS data has a temperature independent exponent γ. Based on this behavior, we build a mastercurve from the literature OKE data and transform it into DLS representation. The mastercurve obtained that way fits nicely our DLS data. We are able to obtain a model independent crossover temperature for several liquids (benzophenone BZP, propylene carbonate (PC), glycerol (GY), propylene glycol (PG), ortho-terphenyl (OTP), decahydroisoquinolin (DHIQ)), at which temperature the onset of the wing first appears and which corresponds to a characteristic relaxation time of τ_x ≈ 10ns. In the high temperature range, where no wing is observable, the apparent width of the α-peak correlates with the relaxation strength of the fast dynamics and anticorrelates with fragility opposite to common wisdom.