Photoassociation of cesium atoms into Cs2 33Πg state at 543.5 nm

We report absorption measurements in pure cesium vapor at high temperatures, when triplet absorption bands in the spectral interval 540-560 nm emerge within the singlet molecular bands which slowly diminish due to efficient thermal dissociation. The absorption bands have been identified as stemming from extrema in the Cs-2 3 (3)Pi(g)-a (3)Sigma(u)(+) difference potential curve. We performed a quasiclassical simulation which agrees well with experimental observation. Since the Cs-2 a 3 Sigma(u)(+) State is only weakly bound, the observed absorption bands at 543.5 and 557 nm represent free-hound transitions or the photoassociation process.