利用激光把中性原子和正离子冷却到超低温是目前比较成熟的技术。在过去四十多年的发展中，激光冷却取得了很多重要成果，并打开了多个激动人心的研究领域。然而，激光冷却负离子到现在还没有被实现，这是由于负离子通常没有激光冷却所需的快速光跃迁循环。通过二十多年的研究，目前人们发现La负离子具有电偶极跃迁允许的束缚态，很有可能可以被激光冷却。但是由于La唯一的稳定同位素139核自旋为7/2，存在较多的暗态，使得激光系统比较复杂。因此很有必要寻找新的可以激光冷却的负离子。项目计划利用新发展的低温离子阱-慢电子速度成像联用的高分辨光电子谱学方法在过渡族、镧系、锕系中搜寻新的可以激光冷却的负离子，测量其能级结构，确定电偶极跃迁的能量和速率。激光冷却负离子的一个重要用途是协同冷却反质子。此外，超冷负离子对冷化学、冷等离子等研究也具有重要意义。

Laser cooling is a well-established technique for the creation of ultracold neutral atoms and positive ions ensembles. This ability has opened many exciting new research fields over the past forty years. However, no negative charged ions has been directly laser cooled because the cycling transition in atomic anions is very rare. La has been chosen as the most promising candidate based on the efforts over twenty years. However，Lanthanum has only one stable isotope 139La. Its nuclear spin is 7/2. This makes the repumping laser system very complicated due to the dark states. Therefore, it is very important to search for new candidates for laser cooling of negative ions. The present project aims to find new candidates in transition metals, lanthanides, and actinides via the slow electron velocity mapping imaging in combination with cold ion trap. The energy levels and the transition rates of promising candidates will be determined. A particularly important application is to sympathetically cool antiprotons in the production of ultracold antihydrogen. Obviously, laser cooling of anions could also open the previously inaccessible research fields in which ultracold negative ions are required, such as the cold chemistry, the cold plasma.