Hybrid spin-exchange optical pumping of 3He -: art. no. 123003

We demonstrate spin-exchange optical pumping of He-3 using a "hybrid" K-Rb vapor mixture. The Rb atoms absorb light from a standard laser at 795 nm, then collisionally polarize the potassium atoms. Spin-exchange collisions of K and He-3 atoms then transfer the angular momentum to the He-3 with much greater efficiency than Rb-He-3. For a K-rich vapor, the efficiency of the hybrid spin-exchange collisions approaches 1/4, an order of magnitude greater than achieved by pure Rb pumping. We present the first measurements of actual photon efficiencies (polarized nuclei produced per absorbed photon), and show that a new parasitic absorption process limits the total efficiencies for both hybrid and pure Rb pumping.