45Sc NMR and high-resolution quasielastic neutron scattering studies of localized H(D) motion in α-ScHx(Dx)

Nuclear magnetic resonance measurements of the 4 5 Sc spin-lattice relaxation rates in the solid solutions α-ScD 0 . 0 5 , α-ScD 0 . 2 2 , and α-ScH 0 . 2 7 have been performed over the temperature range 4.2-299 K and the resonance frequency range 11-86.2 MHz. For all of the samples studied, the 4 5 Sc relaxation rate shows a peak near 100 K resulting from the electric quadrupole interaction modulated by localized hopping of H(D) atoms. In addition to the strong effect of isotope (H↔D) substitution on the amplitude of this peak, with a larger peak appearing in the deuterides, we have found that in the region of the peak, the frequency dependence of the 4 5 Sc relaxation rate for α-ScH 0 . 2 7 is much weaker than for α-ScD x . These results indicate that the hopping rate distribution for H atoms in scandium is shifted to much higher frequencies from that for D atoms. The results of our high-resolution quasielastic neutron-scattering measurements on α-ScH 0 . 2 7 in the temperature range 12-302 K are consistent with this conclusion.