Neutron scattering study of the proton dynamics in acidic solutions

After some preliminary considerations on the abnormally high proton mobility in acid solutions, quasi-elastic neutron scattering results on concentrated sulphuric and nitric solutions are presented. The mean proton translational and rotational diffusive motions are first characterized and compared to those of pure water. Then, the observation of an additional component due to a faster dynamical process is discussed. As this component is also present in concentrated salt solutions, it is concluded that its origin is more related to the peculiar vibrational density of states of electrolyte solutions than to fast proton diffusive. (author). 36 refs.; 6 figs