Photoassociative Spectroscopy of Ultracold NaCs

We present photoassociative spectroscopy of excited states of NaCs below the Na(3S1/2)+Cs(6P3/2) asymptote by ionization detection of ground state molecules. States have been observed as far as 31 cm$^{-1}$ from dissociation and as close as 0.1 cm$^{-1}$ from dissociation. We observe as many as 60 ions per ionizer pulse, implying ground state molecule formation rates as high as 100 kHz.