超低频调制光缔合光谱的实验研究

通过激光冷却技术在磁光阱中俘获原子数约107，温度约200 μK，直径约400 μm的超冷铯原子，利用超冷铯原子光缔合方法制备了激发态的超冷铯分子。实验研究了光缔合光不同扫描速率对铯分子振转光谱分辨率的影响，发现光缔合光扫描速率较慢时，铯分子振转光谱分辨率较高。通过高灵敏的雪崩光电探测器探测冷原子荧光，获得了超冷铯分子第一激发态6S_1/2+6P_3/2离解限0-_g长程态高分辨振转光谱。为了实现受控拉曼光缔合制备超冷基态分子，光缔合激光频率需要锁定在原子-分子共振跃迁线，对超冷原子光缔合光谱进行了超低频波长调制，通过改变调制幅度和调制频率获得最优化的一阶微分信号，将该信号反馈回激光器，实现闭合环路稳频，满足了受控拉曼光缔合制备振转能级可控的基态分子的实验要求，该工作对研究受限空间中的超冷原子分子具有很重要的意义。

Experimental Study of Ultralow Frequency Modulation Photoassociation Spectrum

In the present paper, ultracold cesium atoms were obtained in magnetic optical trap using the laser cooling technology. The number of ultracold atoms is 107. The temperature of ultracold atoms is about 200 μK and the diameter of the ultracold atoms cloud is about 400 μm. The ultracold cesium molecules of excited states were formed using the photoassociation of ultracold atoms. The resolution of vib-rotational spectrum was studied under different scan rates of photossociation laser in the experiment. The resolution of vib-rotational spectrum becomes high when the scan rate of photossociation laser becomes slow. The cold atoms fluorescence was obtained using the high sensitive avalanche photo detector and the high resolution vib-rotational spectrum of ultracold cesium molecule in its first excited state of with dissociation limit long range state was obtained. The ultracold ground molecule was formed by controlled Raman photoassociation and the photoassociation laser must be locked to atom-molecular hyperfine transitions. The ultracold atoms photoassociation spectrum was modulated using ultra-low frequency. The first-order differential signal was optimized by changing modulation amplitude and modulation frequency. It provides a feedback signal to correct error of the laser. The laser frequency satisfies experimental requirement to form ultracold ground molecules using the controlled Raman photoassociation. This work is important for studies of ultracold atoms and molecules in confined space.