In this paper, an ultra-high resolution photoassociation spectroscopy study on photoassociation of cesium atoms is reported. The cold cesium gas in the mag-neto-optical trap is illuminated by a photoassociation laser with red-tuning as large as 40 cm?1 below the 6S1/2 + 6P3/2 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 at-oms. The 0g?, 1g and 0u+ long-range states which correspond to 6S1/2 + 6P3/2 dissocia-tion limit are present in the photoassociation spectrum. The effective coefficients of leading long-range interactions and the corresponding vibrational quantum num-ber 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.
WANG LiRongMA JieJI WeiBangWANG GuiPingXIAO LianTuanJIA SuoTang
We theoretically analysed the linewidth of the probe absorption spectrum in a cold Cs atom–molecule system.The tunnelling coupling between the two excited molecular states,especially for the Cs atom–molecule system,plays an important role in obtaining the sub-natural linewidth of the probe absorption spectrum.For example,when the tunnelling couple strength fulfils σ12 = 10γab1 ,the linewidth is only about 0.66 MHz.Moreover,since the linewidth of interest is dominated by the tunnelling coupling,the absorption peak becomes very narrow even in the case of large pump laser intensities.
