POLARIZATION-DEPENDENT FREQUENCY-SHIFTS FROM RB-HE-3 COLLISIONS

We present measurements of the frequency shift of the Rb electron-para mgnetic-resonance (EPR) line in the presence of nuclear-polariZed He-3 gas for the temperature range of 30 to 85-degrees-C. The frequency sh ift is due to the Fermi-contact interaction between the Rb valence ele ctron and the polarized He-3 nucleus. Expressions for both the frequen cy shift and the spin-exchange cross section are derived in terms of t he strength of this contact interaction. From these expressions and th e measured frequency shift, we estimate the Rb-He-3 spin-exchange cros s section. The Rb EPR frequency shift, which is 53 kHz for a 100% pola rized 10-amagat He-3 sample at 50-degrees-C, can be used to determine the absolute polarization of nuclear polarized He-3 targets. From thes e measurements, one can also predict the shift of the He-3 NMR line du e to a polarized Rb vapor.