Localized Modes in Tantalum Hydrides Studied by Neutron Inelastic Scattering

Abstract

The local vibration spectra of hydrogen atoms dissolved in tantalum have been studied by the energy-loss scattering of pulsed neutrons. The observed time-of-flight spectra show split peaks of the local modes near 120 and 175 meV, which are almost invariant with changing concentration (H/Ta=0.1, 0.5 and 0.7) and configuration of hydrogen at 20° and 85°C. From comparison with previous neutron results on niobium and vanadium hydrides, it is shown that the energies of the split local modes are nearly independent of the metal-hydrogen distance, and the relative intensity and the FWHM of the high energy mode increase in the disordered phase at 85°C in comparison with the ordered phase at 20°C.