Obtaining polarized liquid helium 3 from optically oriented gas

Spin polarized liquid helium three can be obtained by liquefaction of a gas polarized by laser optical pumping. We show that this method can lead to nuclear polarizations exceeding 40 % in a liquid at about 400 mK and almost zero pressure. The relaxation time of the orientation is a few minutes, comparable to the relaxation time of weakly polarized bulk liquid. The NMR signals given by the liquid are strongly shifted in frequency ; this provides a precise and convenient way to measure the polarization and to follow the motion of the liquid inside the experimental cell.