Journal Article

PreJuSER-27240

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Unusual features of long-range density fluctuations in glass-forming organic liquids : a Rayleigh and Rayleigh-Brillouin light scattering in study

Patkowski, A. ; Fischer, E. W. ; Steffen, W. ; Gläser, H. ; Baumann, M. ; Ruths, T. ; Meier, G.FZJ*

2001
APS College Park, Md.

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Please use a persistent id in citations: http://hdl.handle.net/2128/1607  doi:10.1103/PhysRevE.63.061503

Abstract: A new feature of glass-forming liquids, i.e., long-range density fluctuations of the order of 100 nm, has been extensively characterized by means of static light scattering, photon correlation spectroscopy and Rayleigh-Brillouin spectroscopy in orthoterphenyl (OTP) and 1,1-di(4'-methoxy-5' methyl-phenyl)-cyclohexane (BMMPC). These long-range density fluctuations result in the following unusual features observed in a light scattering experiment. which are not described by the existing theories: (i) strong q-dependent isotropic excess Rayleigh intensity, (ii) additional slow component in the polarized photon correlation function, and (iii) high Landau-Placzek ratio. These unusual features are equilibrium properties of the glass-forming liquids and depend only on temperature, provided that the sample has been equilibrated long enough. The temperature-dependent equilibration times were measured for BMMPC and are about 11 orders of magnitude longer than the a process. It was found that the glass-forming liquid OTP may occur in two states: with and without long-range density fluctuations (''clusters"). We have characterized the two states by static and dynamic light scattering in the temperature range from T-g to T-g + 200 K. The relaxation times of the a process as well as the parameters of the Brillouin line are identical in both OTP with and without clusters. The a process (density fluctuations) in OTP was characterized by measuring either the polarized (VV) or depolarized (VH) correlation function, which are practically identical and a-independent. This feature, which is commonly observed in glass-forming liquids, is not fully explained by the existing theories.

Keyword(s): J

Note: Record converted from VDB: 12.11.2012

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Contributing Institute(s):

1. Weiche Materie (IFF-WM)

Research Program(s):

1. Polymere, Membranen und komplexe Flüssigkeiten (23.30.0)

Appears in the scientific report 2001
Notes: This version is available at the following Publisher URL: http://pre.aps.org

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