Highly sensitive photoassociation spectroscopy of ultracold ²³Na¹³³Cs molecular long-range states below the 3S_1/2+6P_3/2 limit

We present high resolution photoassociation spectroscopy of ultracold ²³Na¹³³Cs molecules in a long-range c³∑⁺ state below the (3S_1/2 + 6P_3/2) asymptote. We perform photoassociation spectroscopy in a dual-species magneto-optical trap (MOT) and detect the photoassociation resonances using trap-loss spectroscopy. By fitting the experimental data with the semi-classical LeRoy-Bernstein formula, we deduce the long-range molecular coefficient C₆ and derive the empirical potential energy curve in the long-range region.