Vacancy-induced nuclear-spin-lattice relaxation in solidHe3

New experimental data are presented for the temperature-dependent vacancy-induced nuclear-spin-lattice relaxation times in both the hcp and bcc phases of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. Single-crystal specimens were studied over a range of temperature and magnetic field for which values of the activation energies $\Phi$ and the tunneling frequencies ${\omega }_V$ of vacancies could be obtained with an accuracy hitherto unattained. The values of $\Phi$ and ${\omega }_V$ deduced from the data are compared with previous values obtained from NMR measurements and x-ray diffraction.