High resolution Fourier spectrometry techniques have been used to study the A

The (v = 34, J = 14) level of the A 1 ∑ + u electronic state of Na 2 has been selectively populated by excitation with the 578.1 nm line of a ring dye-laser with rhodamine 6G. Through collisions with ( 2 S 1/2 ) Na atoms, energy is transferred to neighbouring rotational levels in Na 2 , 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 1 ∑ + 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: rot σ total = 0.41 nm 2 .

The A