Moessbauer study of transition metal impurities in niobium hydride

Source and absorber Moessbauer experiments using the resonances of 197Au, 193Ir, 99Ru, 119Sn, and 57Fe in NbHsub(x) (0.7 <approx. x <approx. 1.0) have shown that the electron density at all these probe atoms decreases on hydrogenation. The temperature dependence of the 57Fe Moessbauer spectra was measured up to 500 K. The motion of the probe atoms in the strain fields of the diffusing interstitials gives rise to a broad quasi-elastic Moessbauer absorption line in addition to the narrow elastic part of the spectrum. The temperature dependence of the width of the quasi-elastic line could be observed directly. The data yield quantitative information on the displacement of the probe atoms by the nearest hydrogen neighbours and on the jump rates of the nearest hydrogen neighbours. (Auth.)