Ultracold ground-state molecule production in sodium

We have observed the formation of ground-state Na-2 molecules via the spontaneous decay of excited molecules created by the photoassociation of ultracold atoms. We measure the binding energies of molecules created in three hyperfine components of the lowest singlet and triplet potentials of Na-2 by two different methods. Two of the features are purely triplet a (3)Sigma(u)(+) (v=15) (quasibound) states that have not been previously observed, while the third is a mixed X (1)Sigma(g)(+)-a (3)Sigma(u)(+) state. The molecules are detected with high-resolution cw laser ionization techniques and binding energies are measured to within 10 MHz.