I am aware of the fact that the Havriliak-Negami shape factors are purely empirical parameters that can be used to describe the deviation from the ideal Debye response and as such, they have no immediate physical meaning. Nevertheless several theoretical approaches have been suggested which produce deviations fom the Debye response which can also be fitted by the Havriliak-Negami function either in the frequency domain or in the time domain. I have also heard about various theories of the glassy state where fragility indices and other factors are introduced to describe the deviation of the glassy state from the ideal, interaction-free systems.

Being an exprimental scientis in the applied/industrial area I do not have time to read all these interesting and exciting papers, therefore I ask the following simple questions from the more theoretically inclined colleagues:

1. Do you know cases where the deviaton form the Debye relaxation was measured and fitted by relaxation functions in both dielectric and mechanical response (or maybe NMR)? Is there any relation between the shape factors observed by different experimental methods?

2. According to A.K. Jonshcer (his book on dielectrics) generally there is no relation between the pre-peak and post peak slopes of d(log(eps"))/d(log(omega)) values - i.e. they belong to different processes or mechanisms. Do you agree with this statement?

3. Do you know of relaxation functions that can be fitted to experimental data both in the frequency and time domains, and yield shape factors that have any physical meaning and explanation power for practical applications?

Looking forward to hearing your comments.