Depolarized dynamic light scattering from three low molecular weight glass forming liquids: A test of the scattering mechanism
Patkowski, A. ; Steffen, W. ; Nilgens, H. ; Fischer, E. W.
College Park, Md. : American Institute of Physics (AIP)
Published 1997
College Park, Md. : American Institute of Physics (AIP)
Published 1997
| ISSN: |
1089-7690
|
|---|---|
| Source: |
AIP Digital Archive
|
| Topics: |
Physics
Chemistry and Pharmacology
|
| Notes: |
Depolarized dynamic light scattering (DDLS) experiments are performed on the glass forming materials ortho terphenyl (OTP), bis-methyl-methoxy-phenyl-cyclohexane (BMMPC), and bis-methyl-phenyl-cyclohexane (BMPC). Depolarized spectra are obtained for the bulk liquids and for solutions of varying concentration in CCl4. Effective optical anisotropies of the molecules are obtained from the solution spectra. A detailed analysis of the DDLS spectra, as well as a comparison with the results of quasielastic neutron scattering (QENS) experiments, indicates that the DDLS spectra in the bulk liquids result from at least two physical mechanisms: (i) The low frequency part of the spectrum, in the frequency range of the α peak, arises mainly from the molecular reorientation mechanism. The integrated intensity of this contribution is proportional to the square of the effective molecular anisotropy. (ii) At higher frequencies (but still below the Boson peak), the predominant contribution to the DDLS spectrum arises from interaction-induced scattering. The intensity of this contribution increases with increasing temperature (decreasing density) in the way expected for the cancellation effect. The implications of these results for the comparison of DDLS and QENS experiments and for the comparison of the data to the predictions of mode coupling theories of glass forming liquids are discussed. © 1997 American Institute of Physics.
|
| Type of Medium: |
Electronic Resource
|
| URL: |