A QUANTITATIVE ASSESSMENT OF THE EFFECT OF HYDROGEN-BONDING ON MICROSCOPIC DYNAMICS BY NEUTRON QUASI-ELASTIC SCATTERING

High-resolution ( Delta E=15 mu eV) quasielastic neutron spectra have been measured for liquid methanol (CD3OH) and methane-thiol (CD 3SH) at two temperatures within their liquid ranges. The spectra have been analysed in terms of a previously developed dynamical model which allows for the separation of the translational incoherent parts from the total dynamic structure factors. The strong differences in linewidths of the incoherent functions between the two compounds are then analysed in terms of a phenomenological model which takes into account the existence of several association states in the alcohol. The sulphur compound is then used as a reference fluid in order to carry out a comparative study of the microscopic dynamics of the two materials.