Rotational Energy Transfer within the A 1 Σ u + State of Na 2 Induced by Collisions with ( 2 S 1 / 2 )

The (v′ = 34, J′ = 14) level of the A∑u electronic state of Na2 has been selectively populated by excitation with the 578.1 nm line of a ring dye-laser with rhodamine 6G. Through collisions with (S1/2) Na atoms, energy is transferred to neighbouring rotational levels in Na2, and the density of these levels is determined by observing the fluorescence to the electronic ground state. From previous measurements of the lifetime of the A∑u state and new measurements of the intensities of collision-induced spectral lines, absolute collision cross-sections for all rotational transitions up to ∆J = ±6 have been obtained; the total cross-section for all rotational transitions observed is: rotσ total = 0.41 nm2.