Research on ultracold cesium molecule long-range states by high-resolution photoassociative spectroscopy

In this paper, an ultra-high resolution photoassociation spectroscopy study on photoassociation of cesium atoms is reported. The cold cesium gas in the magneto-optical trap is illuminated by a photoassociation laser with red-tuning as large as 40 cm⁻¹ below the 6S _1/2 + 6P _3/2 dissociation limit, and the photoassociation to the excited state ultracold molecule is detected. High signal-to-noise ratio is obtained by using the lock-in detection of the fluorescence from the modulated cold Cs atoms. The 0 _g ⁻ , 1_g and 0 _u ⁺ long-range states which correspond to 6S _1/2 + 6P _3/2 dissociation limit are present in the photoassociation spectrum. The effective coefficients of leading long-range interactions and the corresponding vibrational quantum number are obtained using LeRoy-Bernstein Law. It is found that photoassociation process creates rotating molecules and the high J value is a hint that higher partial waves participate in the PA process in the presence of trapping laser. Supported by 973 Program of China (Grant. No. 2006CB921603), the National Natural Science Foundation of China (Grant Nos. 10574084, 60678003, and 60778008), the Special Foundation for State Major Basic Research Program of China (Grant No. 2005CCA06300), and the Youth Science Foundation of Shanxi Province of China (Grant No. 20041013)