Study of multiple photoionization processes by multi-electron coincidence spectroscopy

我们采用多电子符合谱法来研究原子和分子的多重光离过程。为此，具有高探测效率的磁瓶飞行时间电子能谱仪和同步辐射脉冲时间结构是非常重要的。对于Ne原子，我们获得了从阈值到200eV的入射光子能量区域的最终状态选择双光离截面，其中两个电子从2s和2p外层电离。这是第一个精确的实验数据，为现有理论提供了严格检验的机会。在Xe原子中，自1976年瑞典研究组首次观测到4p光电子峰的异常行为以来，一直受到人们的关注；4p_<1/2>峰被完全抹去，4p_<3/2>峰呈现复杂结构。我们发现了4d^2双电离的异常增强，并精确地分析了这两个电子之间的能量相关性，揭示了Xe^<2+> 4d^<-2>态是通过Xe+ 4p-1态的Super-Coster-Kronig过程产生的，这是30年前理论上预测的，现在用新的强大的重合光谱实验证明了这一点。此外，我们还研究了CO分子的双光电离，其中一个外层电子与一个C1s或O1ss电子的内层电离同时发射。通过对这两个电子的重合测量，我们发现CO^<2+>态的光谱特征是局域价空穴与核心空穴之间的相互作用。这些结果已在学术期刊上发表，并在国内和国际会议上发表，如下页所示。虽然到目前为止，我们对双光电电离过程感兴趣，其中两个电子起重要作用，我们将发展我们的研究三电子过程，使用一个机械光斩波器完成了这项资助的帮助。实际上，我们已经在Ar三电离方面获得了有趣的结果，很快就会提交到期刊上。少

We have carried out multi-electron coincidence spectroscopy for investigating multiple photoionization processes of atoms and molecules. For this aim, it is very important to have a magnetic bottle time-of-flight electron spectrometer with high detection efficiency, and pulsed time structure of synchrotron radiation. For Ne atoms, we have obtained the final state-selective double photoionization cross sections for the incident photon energy region from the thresholds to 200eV, where the two electrons are ionized from the 2s and 2p outer shells. This is the first precise experimental data supplying an opportunity of rigorous examination for existing theories. In Xe atoms, the abnormal behavior of 4p photoelectron peaks has been paid attention since its first observation by Swedish group in 1976 ; the 4p_<1/2>peak is completely smeared out and the 4p_<3/2>peak is appeared as a complex structure. We have found an abnormal enhancement of 4d^2 double ionization, and analyzed precisely the e … More nergy correlation between these two electrons, which reveals that the Xe^<2+> 4d^<-2> states are produced via Super-Coster-Kronig processes of Xe+ 4p-1 states, which was predicted theoretically 30 years ago, and now proved experimentally with a new powerful coincidence spectOscopy. Furthermore, we have studied double photoionization of CO molecules, where an outer shell electron is simultaneously emitted with inner shell ionization of a C1s or O1ss electron. With coincidence measurements of these two electrons, we have found on the spectral features that the properties of the CO^<2+> states are characterized by the interaction between the localized valence holes and the core holes.These results have been reported in the academic journals and presented at the internal and international conferences as shown in the next pages. While so far we have been interested in double photoionization processes where two electrons makes important roles, we will develop our study three electrons processes, using a mechanical light chopper accomplished with an aid of this grant. Actually, we have already obtained interesting results on Ar triple ionization, which will be submitted to a journal very soon. Less