Generation and manipulation of ultra-cold molecules by coherent photoassociation

冷分子由缓冲气体冷却产生，并经Stark速度过滤器筛选，第一阶段在液氮温度下的碰撞池中制备He缓冲气体，用于热碰撞冷却靶分子。将碰撞池后的靶气体转移到高真空室中进行飞行时间谱检测。通过质谱仪将该分子与缓冲气体区分开。从观察到的飞行时间谱图中，我们可以看到在室温下引入的分子的有效冷却。在乙醛的情况下，获得了130 K的分子束，在下一阶段，在热Maxwel-Bolzmann分布的慢运动分子被四极电场选择。将200 kV/cm的高压施加到电极的1 mm间隙。结果表明，ND_3分子在8 K的速度对应温度下，成功地选择了较低的寻场态。首次采用线电极选择了更高的场搜索态，并对激光冷却技术进行了重新研究，以期将其应用于分子体系。在微K温度下，Rb原子被磁光阱捕获，为超冷分子的制备开辟了途径。该方法适用于一般的具有永久偶极矩的分子，具有重要的意义

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