镧系金属元素电子亲和势的精密测量

电子亲和势是反映原子分子和电子结合能力的一个基本参数，对化学反应、等离子物理、大气物理化学、天体物理等多个领域都很重要。目前大多数镧系元素的电子亲和势还是未知的，有报道的实验测量值误差也较大，约10 meV。由于f电子亚层和d电子亚层没有填满，镧系元素原子负离子电子结构非常复杂。传统的光电子能谱仪的典型能量分辨率10 meV，很难分辨其电子结构。项目计划利用慢电子速度成像方法对镧系元素的电子亲和势进行精密测量，同时得到其负离子能级的精细结构劈裂。将质谱、低温离子阱、慢电子速度成像三种方法联用，可以实现0.5 meV的能量分辨率，可以很好分辨镧系原子分子的复杂电子结构，解决氢化物同位素干扰问题。高分辨谱学数据将为发展相应的理论计算方法提供严格的检验，帮助人们更好地认识镧系金属元素的性质。

Electron affinity (EA) is a fundamental parameter of atoms and molecules. It plays a key role in many fundamental areas, such as chemical reactions, plasma physics, atmosphere chemistry and physics, astrophysics. At current stage, the electron affinities of most of lanthanides remain unknown. Only a few lanthanide elements were measured, and the accuracy of their EAs is quite low. The typical uncertainty is about 10 meV. The electronic structures of lanthanides are very complicated due to the partially filled f and d sub-shell. The energy resolution (~10 meV) of traditional photoelectron spectroscopy cannot resolve the fine structures of atomic ions. We plan to conduct the precision measurement of the electron affinities of lanthanides via the slow electron velocity imaging technique. The combination of the cold ion trap, the mass spectrometer, and the slow electron velocity imaging can achieve the super high energy resolution 0.5 meV, which can well resolve their complicated electronic structures. The super high energy resolution also can solve the isobar issue due to the hydride contamination. The experimental data can server a benchmark for developing more accurate theoretical methods for lanthanides.