H1andD2NMR in stoichiometric PdH (PdD)

The results of ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^2{}_{}{}^{}\mathrm{D}$ nuclear spin-lattice relaxation-rate measurements in stoichiometric PdH and PdD, respectively, indicate an increasing spin density at the proton site, ${\mathrm{}\left[N\right(0\mathrm{}\left)\mathrm{}{H}_{\mathrm{hfs}}\right]}_{\mathrm{H}}$, which correlates with the increase in $T_c$ with increasing hydrogen concentration. An isotope effect is also found {i.e., $\frac{{\mathrm{}\left[N\right(0\mathrm{}\left)\mathrm{}{H}_{\mathrm{hfs}}\right]}_{\mathrm{D}}}{{\mathrm{}\left[N\right(0\mathrm{}\left)\mathrm{}{H}_{\mathrm{hfs}}\right]}_{\mathrm{H}}}>1\mathrm{}$} for the stoichiometric compounds, which could result from the effect of the zero-point displacements smearing out the Fermi-level charge density at the hydrogenic sites.