High-field measurement of the 129Xe-Rb spin-exchange rate due to binary collisions

We have measured the binary spin-exchange rate coefficient for collisions between Rb and 129Xe atoms at a magnetic field B=9.4 T and in the temperature range 160<T<200 deg. C. The longitudinal spin-relaxation rate 1/T1 of 129Xe is dominated by 129Xe-Rb binary collisions. We measured 1/T1 using the methods of conventional nuclear magnetic resonance, with no spin enhancement by optical pumping. At the high magnetic field and large gas pressures used in this work, the contribution of 129Xe-Rb molecules to the spin-exchange rate was less than 0.1% of the binary-collision rate. The Rb atomic number density [Rb] was measured directly from the large Faraday rotation of the polarization of near-resonant light passing through the sample cells. The rate coefficient is κ=d(1/T1)/d [Rb]=(1.75±0.12)x10-16 cm3/s