Proton Dynamics in Palladium-Silver: An Inelastic Neutron Scattering Investigation

Proton dynamics in Pd_{77}Ag_{23} membranes is investigated by means of various neutronspectroscopic techniques, namely Quasi Elastic Neutron Scattering, Incoherent Inelastic NeutronScattering, Neutron Transmission, and Deep Inelastic Neutron Scattering. Measurements carriedout at the ISIS spallation neutron source using OSIRIS, MARI and VESUVIO spectrometers wereperformed at pressures of 1, 2, and 4 bar, and temperatures in the 330-673 K range. The energyinterval spanned by the different instruments provides information on the proton dynamics in a timescale ranging from about 10^2 to 10^{-4} ps. The main finding is that the macroscopic diffusion process isdetermined by microscopic jump diffusion. In addition, the vibrational density of states of the Hatoms in the metal lattice has been determined for a number of H concentrations and temperatures.These measurements follow a series of neutron diffraction experiments performed on the samesample and thus provide a complementary information for a thorough description of structural anddynamical properties of H-loaded Pd-Ag membranes.