This title appears in the Scientific Report : 2001 
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.
Weiche Materie; IFF-WM
Physical Review E Physical review / E, 63 63 (2001 2001) 6 6, S. 061503 061503
College Park, Md. APS 2001
2001-05-23
2001-05-01
061503
10.1103/PhysRevE.63.061503
Journal Article
Polymere, Membranen und komplexe Flüssigkeiten
Physical Review E 63
J
OpenAccess
Please use the identifier: http://dx.doi.org/10.1103/PhysRevE.63.061503 in citations.
Please use the identifier: http://hdl.handle.net/2128/1607 in citations.


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.