H-2 NMR in nearly stoichiometric yttrium dideuteride

H-2 NMR spectra and spin-lattice relaxation rates: R-1 are measured as func tions of temperature (4.2-310 K) for YD1.99 and YD1.99+0.04 In YD1.99 the m easured temperature dependence of R1 is explained by the interaction of deu teron spins with conduction electrons and the value 7.56 x 10(-5) s(-1) K-1 is obtained for the inverse Korringa product R-1e/T. Most of she spectral features in the "rigid" lattice regime are described by the dipolar interac tion. No evidence of the deuterium self-diffusion was observed in the measu red temperature range. The low-temperature spectra ill YD1.99+0.04 consiste d of two components: a central line and a doublet characteristic for the qu adrupole interaction. The central line corresponds to zero electric field g radients (EFG) at the sites of the deuterons which have a surrounding: with cubic symmetry like in YD1.99 The doublet indicates a non-zero EFG which c an be explained in terms of the presence of short-range ordered domains of the hypothetical YD2.25 stoichiometry. Other possible interpretations of th e spectra are also discussed. In the vicinity of 250 K both spectra and R-1 reflect the onset of the rapid motion of deuterium atoms. The linear depen dence of R-1 at low temperatures yields R-1e/T = 6.35 x 10(-5) s(-1) K-1.