Intercombination transitions b3Πu ← X1Σg+ in Na2

The weak intercombination band b (3) Pi(u)(upsilon(b) = 0) <-- X (1) Sigma(g)(+)(upsilon " = 0) of Na-2 molecules formed in a supersonic beam has been excited directly with a pulsed narrow-band dye laser and recorded with rotational resolution, Molecular constants of the b (3) Pi(u) state are derived and compared with results in the literature, obtained with other techniques. The different perturbation mechanisms are discussed. (C) 1997 Published by Elsevier Science B.V.