HIGH NUCLEAR-POLARIZATION IN HE-3 AND HE-3-HE-4 GAS-MIXTURES BY OPTICAL-PUMPING WITH A LASER-DIODE

New diode lasers delivering 50 mW output power at 1083 nm are shown to be efficient sources for optical pumping of helium. They can polarize nuclei in a He-3 gas up to M = 50% over the pressure range 0.4-1.6 to rr. Larger nuclear polarizations M of He-3 nuclei, of order 80%, can b e obtained in He-3-He-4 mixtures when the laser frequency is tuned to a He-4 line. A standard optical measurement of nuclear polarization M has been extended to the case of He-3-He-4 mixtures. The effect of var ious parameters on the steady-state polarization M and on the pumping time T-p is discussed.