High nuclear polarization in3He and3He-4He gas mixtures by optical pumping with a laser diode

Abstract

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 a3He gas up toM = 50% over the pressure range 0.4–1.6 torr. Larger nuclear polarizationsM of3He nuclei, of order 80%, can be obtained in3He-4He mixtures when the laser frequency is tuned to a4He line. A standard optical measurement of nuclear polarizationM has been extended to the case of3He-4He mixtures. The effect of various parameters on the steady-state polarizationM and on the pumping timeTp is discussed.