[en] 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 approx. 20, 20, and 100 A². The cross sections rise from approx. 0.1 A² at n approx. 6 to a plateau at n approx. 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