Generation and manipulation of ultra-cold molecules by coherent photoassociation

通过缓冲气体冷却产生冷分子，并通过Stark速度过滤器进行筛选；第一阶段，在碰撞池中制备液氮温度下的He缓冲气体，用于热碰撞冷却目标分子。碰撞池后的目标气体被转移到高真空室进行飞行时间光谱的探测。用质谱仪将该分子从缓冲气体中区分出来。从飞行光谱的观测时间可以看出，在室温下引入的分子是有效冷却的。在乙醛的情况下，获得了130K的分子束，在下一阶段，利用四极电场选择了热Maxwel-Bolzmann分布的慢运动分子。在电极间隙1 mm处施加200KV/cm的高压。结果表明，在速度对应温度为8K的条件下，成功地选择了Nd3分子的低场搜索态，并首次用线电极选择了高场搜索态。最后，还对激光冷却技术进行了重新研究，以期在未来的分子体系中得到应用。利用磁光囚禁技术在微K温度下对Rb原子进行了囚禁，为制备超冷分子开辟了新的途径。这将具有重要意义，因为该方法适用于具有永久偶极矩的一般分子。

Cold molecules were produced by buffer gas cooling and selected by Stark velocity filter.At first stage, He buffer gas in the collision cell at the temperature of liquid nitrogen was prepared for cooling the target molecules by thermal collision. The target gas after the collision cell was transferred to high vacuum chamber to detect time of flight spectrum. The molecule was distinguished by mass spectrometer from the buffer gas. From the observed time of flight spectrum we could see the effective cooling of the molecule which was introduced at the room temperature. In the case of acetaldehyde, molecular beam of 130K was obtained.In the next stage, slow moving molecules in the thermal Maxwel-Bolzmann distribution were selected by quadra-pole electric field. High-voltage of 200kV/cm was applied to the 1mm gap of the electrodes. As a result, the lower filed seeking states of the ND_3 molecule were successfully selected with the velocity corresponding temperature of 8 K. The higher field seeking states were also selected by the wire electrode for the first time.And finally, laser cooling technique was also reinvestigated in order to apply for molecular system in the future. Rb atom was trapped by magneto optical trap at the temperature of micro K By these studies, the way to ultra cold molecules is developed. It would be significant because the way is applicable to general molecules with permanent dipole moment