Very Long Nuclear Spin Relaxation Times in GaseousHe3by Suppression ofHe3-Surface Interactions

Experiments are described that reveal the nature of the surface relaxation mechanisms between ${\mathrm{He}}^3$ atoms and their containing walls, and effective means for their suppression. The resultant very long ${\mathrm{He}}^3$ relaxation times (>2×${10}^5$ sec at 300°K, and rising rapidly with temperature) measured in highly spin-polarized samples prepared by optical pumping offer new possibilities for high-density polarized ${\mathrm{He}}^3$ nuclear targets, and for experiments requiring near-perfect gyroscopes.