The latest electron affinity value of an iridium atom is 1.564 36(15) eV, determined via a method based on the Wigner threshold law by Bilodeau and co-workers. However, they observed a significant deviation from the Wigner threshold law in the threshold photodetachment experiment. To address this dilemma, we conducted high-resolution photoelectron spectroscopy of Ir- via the slow-electron velocity-map imaging method in combination with an ion trap. The electron affinity of Ir was measured to be 12 614.97(9) cm-1 or 1.564 057(11) eV. We find that the Wigner threshold law is still valid for the threshold photodetachment of Ir- through a p-wave fitting of the photodetachment channel Ir-5d86s23F4→Ir5d86sb4F9/2. The photoelectron angular distributions of photodetachment channels Ir-5d86s23F4→Ir5d76s2a4F9/2 and Ir-5d86s23F4→Ir5d86sb4F9/2 were also investigated. The behavior of anisotropy parameter β indicates a strong interaction between the two channels. Moreover, the energy level 3P2 of Ir-, which was not observed in the previous works, was experimentally determined to be 4163.24(16) cm-1 above the ground state.

中文翻译：

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铱原子的电子亲和力和铱阴离子的光电子角分布的测量。

铱原子的最新电子亲和力值为1.564 36（15）eV，这是由Bilodeau及其同事通过基于Wigner阈值定律的方法确定的。但是，他们在阈值光解实验中观察到了与维格纳阈值定律的显着偏离。为了解决这个难题，我们通过慢电子速度图成像方法结合离子阱进行了Ir-的高分辨率光电子能谱。Ir的电子亲和力经测量为12 614.97（9）cm-1或1.564 057（11）eV。我们发现，通过光解离通道Ir-5d86s23F4→Ir5d86sb4F9 / 2的p波拟合，Wigner阈值定律对于Ir-的光解阈值仍然有效。还研究了光分离通道Ir-5d86s23F4→Ir5d76s2a4F9 / 2和Ir-5d86s23F4→Ir5d86sb4F9 / 2的光电子角分布。各向异性参数β的行为表明两个通道之间有很强的相互作用。此外，通过实验确定Ir-的能级3P2在以前的工作中没有观察到，实验确定为高于基态4163.24（16）cm-1。