PALEY-WIENER CRITERION FOR RELAXATION FUNCTIONS

The conclusion [K. L. Ngai, A. K. Rajagopal, R. W. Rendell, and S. Tei tler, Phys. Rev. B 28, 6073 (1983)] that simple exponential decay is a nonviable model for electrical relaxation, because it fails to satisf y the fundamental Paley-Wiener Fourier transform criterion, is shown b y direct analysis to be inapplicable to small-signal electrical relaxa tion situations. Thus, not only is exponential decay and its associate d single-relaxation-time Debye frequency response a valid model for re laxation, but, by extension, all distributions of relaxations times an d energies which use a superposition of simple exponentials or Debye f unctions are also acceptable descriptions of relaxation phenomena. Rea sons why the earlier conclusion is nonviable in the present context ar e discussed. (C) 1997 American Institute of Physics.