镥原子自电离态的共振电离谱

Resonance ionization spectrum of autoionization states of lutetium atom

^(177)Lu是一种用于成像引导放射性治疗的重要医用同位素,可通过辐照高丰度^(176)Lu或^(176)Yb的方式生产,通过同位素分离手段获取高丰度^(176)Lu辐照前体是解决世界范围内^(177)Lu供应不足问题的必要途径.由于镥同位素无法通过离心分离方式生产,需要发展多步多色光电离方法以获取高丰度^(176)Lu,但镥原子的自电离态能级数据稀缺,限制了高效光电离路径的构建.激光共振电离谱是少数具有自电离态研究能力的激光光谱学方法之一,利用实验室搭建的激光共振电离飞行时间质谱系统,测量得到激发态35274.5 cm^(-1)的能级寿命为(31.6±1.7)ns;由该激发态出发,利用三色三步光电离方案,扫描了镥的50560—53450 cm^(-1)能区,获取了47条自电离态能级,其中33条为首次发现,确定了自电离跃迁的峰宽和相对跃迁强度,提供了可见光波段内可用于镥原子高效光电离的关键光谱数据.同时,为确定自电离态能级的电子组态,通过3条不同J值激发态的扫描实验,标识了21条能级的角动量,为确定自其他激发态出发的电偶极跃迁禁戒情况提供了参考依据.

^(177)Lu is an important medical isotope used in imaging-guided radiotherapy,and it can be produced by irradiating ^(176)Lu or ^(176)Yb with high abundance.With an increasing demand for medical isotopes,it is very essential to improve the supply capacity for ^(177)Lu.The multi-step multi-color photoionization method is an effective method to obtain isotopes,and the information of odd-parity autoionization levels is essential.Laser resonance ionization spectroscopy is one of a few spectroscopic experimental methods that can study autoionization levels.An experimental system is developed for the frontier spectroscopic research,and it consists of custom-made tunable lasers and a high-resolution time of flight mass spectrometer.The lifetime of the excited state 35274.5 cm^(−1) is measured to be(31.6±1.7)ns by the delayed photoionization method for the first time.A three-step three-color photoionization process is used to detect the autoionization levels,with a delay of 30 ns between l2−l1 and l3−l2 respectively,in order to avoid any unexpected transitions.Forty-seven odd-parity autoionization levels are obtained,of which 33 levels are discovered for the first time,and the l2 and l1 are blocked to exclude possible interference peaks,such as the l1+l3+l3 transition.Several autoionization levels show asymmetrical peak shapes,and the Fano fitting is carried out for all the levels to determine the widths and relative transition strengths of the autoionizing transitions.This study provides critical data for the high-efficient photoionization of lutetium atoms in the visible range.The angular momenta of 21 odd-parity autoionization levels in an energy range of 50650−51650 cm^(−1) are identified for the first time,which provides a reference for determining the forbidden state of electric dipole transitions from other excited states and ascertaining the electronic configuration.