We report extensive new measurements of the longitudinal relaxation time $T_1$ of ${}^{129}\mathrm{Xe}$ nuclear spins in solid xenon. For temperatures $T<\mathrm{}120\mathrm{}\mathrm{K}$ and magnetic fields $B>\mathrm{}0.05\mathrm{}\mathrm{T}$, we found $T_1$ on the order of hours, in good agreement with previous measurements and with the predicted phonon-scattering limit for the spin-rotation interaction. For $T>\mathrm{}120\mathrm{}\mathrm{K}$, our new data show that $T_1$ can be much shorter than the phonon scattering limit. For $B=0.06\mathrm{}\mathrm{T}$, a field often used to accumulate hyperpolarized xenon, $T_1$ is $\sim 6\mathrm{s}$ near the Xe melting point $T_m=161.4\mathrm{}\mathrm{K}$. From $T=50\mathrm{}\mathrm{K}$ to $T_m$, the new data are in excellent agreement with the theoretical prediction that the relaxation is due to (i) modulation of the spin-rotation interaction by phonons, and (ii) modulation of the dipole-dipole interaction by vacancy diffusion.

• Received 15 January 2002

DOI:https://doi.org/10.1103/PhysRevLett.88.147602