Photoassociation of cesium atoms into the double minimum Cs2 3 1Σ u+ state

We have observed the transition from the free colliding pair of cesium atoms into the outer well of the double minimum Cs₂ 3 ¹Σ _u⁺ state. This photoassociation process takes place in a cesium vapor consisting predominantly of atoms, in which dimers have been about 85% thermally dissociated. Excellent agreement with quasiclassical simulations was found. We discuss the possibility of using a double minimum Cs₂ 3 ¹Σ _u⁺ state for the formation of ultracold Cs₂ X ¹Σ _g⁺ molecules.