%0 Journal Article
%A Ngai, K. L.
%A Lunkenheimer, P.
%A León Yebra, Carlos
%A Schneider, U.
%A Brand, R.
%A Lodl, A.
%T Nature and properties of the Johari-Goldstein β-relaxation in the equilibrium liquid state of a class of glass-formers
%D 2001
%@ 0021-9606
%U https://hdl.handle.net/20.500.14352/59632
%X Previous dielectric relaxation measurements of glycerol and propylene carbonate and new results on propylene glycol performed below the conventional glass transition temperatures T_(g) after long periods of aging all show that the excess wing (a second power law at higher frequencies) in the isothermal dielectric loss spectrum, develops into a shoulder. These results suggest that the excess wing, a characteristic feature of a variety of glass-formers, is the high frequency flank of a Johari–Goldstein β-relaxation loss peak submerged under the α-relaxation loss peak. With this interpretation of the excess wing assured, the dielectric spectra of all three glass-formers measured at temperatures above T_(g) are analyzed as a sum of a α-relaxation modeled by the Fourier transform of a Kohlrausch–Williams–Watts function and a β-relaxation modeled by a Cole–Cole function. Good fits to the experimental data have been achieved. In addition to the newly resolved β-relaxation on propylene glycol, the important results of this work are the properties of the β-relaxation in this class of glass-formers in the equilibrium liquid state obtained over broad frequency and temperature ranges.
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