Wall Relaxation ofH3ein Spin-Exchange Cells

The ${}^3\mathrm{He}$ longitudinal spin-relaxation rate $T_1^{-1\mathrm{}}$ is crucial for production of highly polarized ${}^3\mathrm{He}$ by spin-exchange optical pumping. We show that $T_1^{-1\mathrm{}}$ is increased by a factor of 2–20 solely by exposure of spin-exchange cells to a few-kG magnetic field. The original $T_1^{-1\mathrm{}}$ can be restored by degaussing the cell. The effect is attributed to magnetic surface sites and has been observed in both Pyrex and aluminosilicate-glass cells. Our results both advance the understanding of wall relaxation and demonstrate the use of ${}^3\mathrm{He}$ as an extremely sensitive probe of surface magnetism.