Nuclear Spin-Lattice Relaxation in Liquid Nontransition Metals

We develop a broad interpretation for nuclear spin-lattice relaxation in liquid nontransition metals using our new data for ${\mathrm{Bi}}^{209}$ and previously reported data for ${\mathrm{Ga}}^{69,71}$, ${\mathrm{Rb}}^{85,87}$, ${\mathrm{Sb}}^{121,123}$, ${\mathrm{Na}}^{23}$, and ${\mathrm{In}}^{115}$. Our work provides new insight into the relative importance of the various contributions to the NMR shift $K$ and the nuclear spin-lattice relaxation rate $R_1$. The three potentially significant contributions to $K$ are the hyperfine contact $K_s$, hyperfine orbital $K_{\mathrm{o}}$, and core polarization $K_{\mathrm{cp}}$. All other contributions to $K$ are negligible. The sum of $K_{\mathrm{o}}$ and $K_{\mathrm{cp}}$ is small compared to $K_s$ even in heavy elements. The first significant contribution to $R_1$ is the hyperfine contact rate $R_{1s}$, expressed by the Korringa relation, with $K\left(\alpha \right)$, the correction factor for electron-electron interactions, having a reasonable value of about 0.75 for all metals in our study. The second and last non-negligible contribution to $R_1$ is the nuclear quadrupole rate $R_{1q}$ arising from the effect of ionic motion on the conduction electrons, whose magnitude decreases with an increase in temperature.