Collisional Depopulation of Excited Na s States by Rare Gas Atoms

Our work bias motivated by measurements made by Gallagher and Cooke on depopulation cross sections of Na s states from n = 6 to 11 due to collision with He, Ar and Xe atoms at thermal velocities. These cross sections were much smaller than those associated with collisional ℓ mixing, the maximum values for He, Ar and Xe being ~20, 20 and 100 A 2 . They rose from ~0.1 A 2 at n~6 to a plateau at n~10. The small size of the cross sections suggests that the depopulation proceeds through direct interaction between the Na + core and the rear gas atom.