Light-induced drift in rubidium: Spectral dependence and isotope separation

Abstract

We report on the frequency dependence of the light-induced drift velocity of rubidium in argon buffer gas. The sign of the drift velocity is found to closely follow the sign of the derivative of the low-intensity absorption spectrum. This is in disagreement with previous predictions and is qualitatively different from the sodium case. Numerical studies agree with our observations, and point to the importance of the ratio of the ground-state hyperfine splitting to the Doppler width. These observations imply that the two naturally occuring isotopes 85Rb and 87Rb can be easily separated using light-induced drift, and this is experimentally demonstrated.