Formation of ultracold X 1Σ+(v=0) NaCs molecules via coupled photoassociation channels

We report production of ultracold X (1)Sigma(+)(v '' = 0) NaCs molecules via photoassociation. We utilize a combination of spectroscopic techniques to determine formation pathways and label ground-state samples. Efficient free-bound excitation occurs due to coupling between B-1 Pi and neighboring electronic states in the Na 3S + Cs 6P complex. An f-wave shape resonance contributes to formation of a rotationally pure sample of X (1)Sigma(+)(v '' = 0, J '' = 1) molecules.