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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.10: Poster

Donnerstag, 29. März 2001, 15:45–18:15, Foyer S\ 3

Glass dynamics and scaling behaviour under pressure using quasielastic nuclear forward scattering — •Tanja Asthalter^1,2, Ilia Sergueev^1,2, Hermann Franz^3,2, Winfried Petry², Kirill Messel^3,2, and Roberto Verbeni¹ — ¹ESRF, B.P. 220, F-38043 Grenoble Cedex — ²Experimentalphysik E13, TU München, James-Franck-Str., D-85747 Garching — ³DESY/Hasylab, Notkestr. 85, D-22603 Hamburg

Varying pressure as well as temperature is essential for validity tests of various theories of glass dynamics, such as the still popular free-volume model or the mode-coupling theory. We have applied quasielastic nuclear forward scattering of synchrotron radiation under pressure on dibutylphthalate doped with 5 atomic % ferrocene (enriched to 95.3 % in ⁵⁷Fe). Our experiment was carried out at the new beamline ID22N at the European Synchrotron Radiation Facility. The decay rate of delayed nuclear resonant quanta provides information about the self-correlation function F_s(q,t) of the resonant nuclei and thus about relaxation times on the timescale of the Mößbauer nuclei (141.1 ns for ⁵⁷Fe). Using known V,P data and thermal expansion coefficients and applying the Tammann-Tait equation to calculate the density, we can plot the relaxation times versus density. Our results show that – in analogy to the study on OTP – the diffusion times do not show the same scaling behaviour, depending on whether density is changed by applying pressure or by heating. Thus we conclude that the validity of the free-volume model is disproved for the case of high scattering vectors/ short length scales.