No Access Submitted: 01 August 2009 Accepted: 12 October 2009 Published Online: 13 November 2009
J. Chem. Phys. 131, 184510 (2009);
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Dielectric loss spectra of glass forming liquids are analyzed, with emphasis on systems for which a peak due to a secondary relaxation is not immediately obvious. Thus, glass formers are considered for which the high-frequency flank of the α-relaxation peak appears to be dominated by a so-called wing contribution. It is shown that even for such supercooled liquids the shape of the α-peak has to be characterized by two parameters. By performing a series of aging experiments it is demonstrated that the high-frequency flank of the α-relaxation, assumed to follow a power-law behavior, is superimposed by contributions from an excess wing and from a β-relaxation peak. In particular, the excess wing, previously associated with either the α- or the β-relaxation, is identified as a feature that evolves in its own right. It is argued that excess wing and β-relaxation are always present albeit with relative strengths that may vastly differ from glass former to glass former.
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