Photoassociative Ionization of Heteronuclear Molecules in a Novel Two-Species Magneto-optical Trap

We describe the experimental observation of ultracold NaCs⁺ molecular formation in a novel two-species magneto-optical trap. We interpret our observations in terms of a photoassociative ionization pathway similar to that observed in a sodium trap: Na+Cs+ωNa+ωCs→NaCs⁺+e^-. We have directly measured the NaCs⁺ production rate as a function of the excitation laser frequency and intensity elucidating the role of ground-state hyperfine levels. We have observed resonance structures in the frequency-dependent ion rate which we associate with the molecular character of the process.