Quasi‐Elastic Neutron Scattering on Hydrogen in Niobium Single Crystals

Abstract

Abstract Quasi‐elastic neutron scattering experiments on the system NbH 0.07 have been performed with Niobium single crystals at T = 235 and 256 °C. The width of the quasi‐elastic line has been measured 1) for fixed momentum transfer | x |, changing the angle between x and a reference plane of the crystal, and 2) dependent on | x |, the x ‐vector parallel to three symmetry directions. The results have been compared with theoretical half widths corrected for experimental resolution. They favour the tetrahedal site model assuming simple jump diffusion. However, in the (001) direction deviation from the predicted behaviour occurs and the obtained value of the mean residence time differs by a factor of two from that derived from the macroscopic diffusion constant assuming tetrahedral sites.