Proton nuclear magnetic resonance was measured in two Nb–H samples which had been prepared so as to introduce vacancy–H clusters, and in a reference sample which did not contain vacancy–H clusters. A motionally narrowed signal which persisted to very low temperatures was observed only in the former samples, and was attributed to protons which executed caged motions in Nb-atom vacancies. From the temperature dependence of the line-width, between 7 and 30K, an apparent activation energy of 0.0038eV was deduced. NMR Studies of Hydrogen Motion in Vacancies in Nb–H Alloys. T.Imai, A.Kayanuma, Y.Fukai, S.Masubuchi: Journal of Physics - Condensed Matter, 2004, 16[46], 8191-200