Improvement of signal-to-noise ratio of the Cs2 photoassociation spectroscopy by using dark SPOT magneto-optical trap

► We have obtained of long-range PA spectroscopy of cesium atoms in dark SPOT. ► We employed frequency modulation technique to obtain high sensitivity spectroscopy. ► The signal-to-noise ratio of spectroscopy in dark SPOT is enhanced to 115.6. ► The method effectively improving the detection sensitivity of spectroscopy.