Relaxation Dynamics of Cascaded Linear Processes

Titelangaben

Kador, Lothar ; Bausinger, R. ; Leopold, André ; Haarer, Dietrich ; Köhler, Werner:
Relaxation Dynamics of Cascaded Linear Processes.
In: The Journal of Physical Chemistry A. Bd. 108 (2004) . - S. 1640-1643.
ISSN 1520-5215
DOI: https://doi.org/10.1021/jp030963v

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Abstract

In many fields of nature, a system reacts to sudden changes of an external parameter in the form of two (or more) cascaded relaxation processes, where the first step depends directly on the external parameter and the second process, which is connected with the experimental observable, is determined by the state of relaxation of the first one. It follows from linear-response theory that in this case the experiment yields a behavior which distinctly deviates from a single-exponential decay, even if each of the processes is linear and follows an exponential law. The relaxation starts with time derivative zero, which is most pronounced when the two time constants are of similar magnitude. If the experimental data are fitted with a Kohlrausch\textminusWilliams\textminusWatts (KWW) function, the fit will therefore tend to overestimate the KWW exponent β. Even β values larger than one can be obtained. As an example, the diffracted light signal in a photorefractive polymer is analyzed.