Collisional depopulation of excited Nasstates by He, Ar, and Xe

The authors have measured the collisional depopulation cross sections of Na s states from n=6 to 11. The maximum cross sections observed for He, Ar, and Xe, respectively, are {~}20, 20, and 100 ². The cross sections rise from {~}0.1 ² at n~6 to a plateau at n~10. The small size of the cross sections suggests that the process proceeds via the interaction of the Na⁺ core with the rare-gas atom. Specifically, this short-range interaction produces a transient dipole on the rare-gas atom which efficiently couples Na states of different n. This is an entirely different mechanism than that responsible for the collisional l mixing previously reported.