Observation of an incoherent thermally activated proton hopping process   in calix-[4]-arene by means of anelastic spectroscopy
  The anelastic spectrum of calix[4]arene was measured at two different vibrational frequencies. Three thermally activated peaks were detected. The lowest temperature peak can be described considering a continous distribution function of activation energies for the relaxation. This anelastic peak can be ascribed to a thermally activated hopping process of H atoms of the OH groups, corresponding to a flip-flop of the OH bond. From the results of the present study, it seems that anelastic spectroscopy is a good experimental technique to study atomic motion inside molecules at a mesoscopic (few molecules) level. 
A. Paolone, R. Cantelli, R. Caciuffo, A. Arduini