Temperature dependence of diffusion coefficients for rubidium-inert gas mixtures using coherent scattering

We have recently measured diffusion coefficients D for naturally abundant Rb atoms in 6 buffer systems (He, Ne, N2, Ar, Kr and Xe) using coherent scattering from an optically pumped Rb population grating. These measurements, which were carried out at a temperature of T = 24 ℃, have combined statistical and systematic uncertainties ranging from 5.5% to 15%, and agree with quantum mechanical and classical calculations (Pouliot et. al, Submitted Phys. Rev. A). Our results suggest that it is possible to develop a quantum pressure sensor from diffusion measurements by reducing systematic effects, and by measuring the temperature dependence of D. We report progress on these measurements by (i) modifying the design of our oven to vary the temperature over approximately 100 ℃, (ii) using PMT detection to eliminate systematic effects from the heterodyne detection system, (iii) spatially filtering the excitation beams to reduce wavefront curvature, and (iv) expanding beam size to reduce transit time effects.