Trapping molecular ions formed via photo-associative ionization of ultracold atoms

The formation of Ca-40(2)+ molecular ions is observed in a hybrid Ca-40 magneto-optical and ion trap system. The molecular ion formation process is determined to be photo-associative ionization of ultracold Ca-40 atoms. A lower bound for the two-body rate constant is found to be (beta) over bar >= 2 +/- 1 x 10 (15) cm(3) Hz. Ab initio molecular potential curves are calculated for the neutral Ca-2 and ionic Ca-2(+) molecules and used in a model that identifies the photo-associative ionization pathway. As this technique does not require a separate photo-association laser, it could find use as a simple, robust method for producing ultracold molecular ions.