Measurement of the ²¹Ne Zeeman frequency shift due to Rb-²¹Ne collisions

Using a ²¹Ne-³He Zeeman maser, we compared the frequency shift of the ²¹Ne nuclear Zeeman resonance induced by polarized Rb vapor to the shift induced in the ³He nuclear Zeeman resonance. The ³He-Rb shift has recently been measured with high precision [M.V. Romalis and G.D. Cates, Phys. Rev. A 58, 3004 (1998)], permitting the conversion of our differential measurement to an absolute value for the ²¹Ne-Rb shift. We report a value of κ₂₁=32.0±2.9 for the Rb-²¹Ne contact shift enhancement factor at a temperature of approximately 128°C. We also propose high-precision differential contact shift measurements, the absolute accuracy of which could be limited by the error in the ³He contact shift.