New relaxation peaks at liquid helium temperatures due to the motion of hydrogen in trap sites around Ti in Nb

The presence of hydrogen in niobium containing 5 at. % alloying titanium gives rise to new relaxation processes at liquid helium temperatures. The effects have been studied for two H concentrations (0.08 and 0.48 at. %), and by exciting two resonance modes of the specimen (20 and 74.5 kHz). The temperatures at which the processes occur are independent of H content and their intensities increase with increase of the H concentration. At the lower resonance frequency the peaks shift towards lower temperatures and their intensities markedly decrease. This latter behavior may be explained by a delocalized tunneling model for hydrogen trapped by Ti.