Quasi-linear least squares and computer code for numerical evaluation of relaxation time distribution from broadband...

We present a new fitting procedure and computer code for numerical evaluation of dielectric relaxation time distribution functions. The technique is based on linear least squares minimization and aims primarily at the analysis of compound experimental spectra of complex dielectric permittivity. It is fast, robust, and easy to use. No prior knowledge about the number of relaxation modes, their characteristic times, relaxation strengths, or the functional form of the underlying relaxation time distribution function is required, the procedure determines these parameters instead. The method is tested by both synthetic spectra with well-defined parameters of dielectric relaxation and experimental wide-band dielectric spectra of different types. We believe that this new fitting instrument, which allows an unbiased approach to the formal description of dielectric spectra, may be of interest in many areas of dielectric spectroscopy.