Neutron Spectroscopic Studies of Dilute Hydrogen in Pure and Defected Metals
A review is presented of recent work at NBS on the study of vibration spectra of hydrogen isotopes bound at low concentration (⪝1%) in both pure metals and metals containing interstitial and substitutional traps. Results will be discussed for neutron spectra of Nb, Ta, V, and Pd-hydrogen systems, including preliminary work on palladium and titanium alloys and studies of isotope dependence. Spectroscopic results for hydrogen trapped by O, N, and Ti impurities will be discussed in detail and compared to other systems which do not exhibit trapped states at low temperature. The implications of these results in terms of models for the local environment of trapping sites will be considered. Very recent neutron data on the concentration dependence of local modes in α- and β-phase palladium hydrides and deuterides will also be presented.