Study on Multielectron Effect Near Molecular Inner-Shell Photoionization Thresholds

UVSOR的双环分析仪(DTA)最初是由一个法国集团开发的，目前正在进行调试。没有任何出射狭缝的成像探测使我们能够同时观察到能量范围超过通过能量的10%的电子及其角分布。最近证实，经过差热分析的重新组装和仔细的调试，分析仪的性能有了很大的改善。带二维探测器的离子飞行时间光谱仪正处于计划阶段，用于进行能量选择电子-离子符合实验。在研究和开发新的实验装置的同时，还进行了一些试验性实验，用于观察分子内壳激发后的次要产物，如高激发的中性物质和阴离子。由于N^*的形成，在N_2分子的1s阈值附近观察到了很强的增强作用。研究发现，导致N^*形成的高激发态N_2^&lt；+^*&gt；是由核激发态的旁观者俄歇衰变以及慢光电子重新俘获到里德堡轨道所填充的。结果表明，亚稳态观测是研究核激发态衰变动力学和后碰撞相互作用引起的光电子再俘获的一种新的灵敏工具。对于分子内层激发后的阴离子成像检测，我们遇到了消除电子背景噪声的困难，这种背景噪声可以通过时间分辨实验来解决。

The double toroidal analyzer (DTA) at UVSOR, which has been originally developed by a French group, has been under conditioning. The imaging detection without any exit slit enables us to observe electrons within an energy range more than 10% of the pass energy, and their angular distributions simultaneously. Recently it was confirmed that the performance of the analyzer has been improved considerably, after re-assembling of DTA and its careful tuning. The introduction of an ion time-of-flight spectrometer with a two dimensional detector is in the planning stage, to perform energy-selected-electron-ion coincidence experiments.Parallel to the research and development of new experimental setups, some trial experiments have been made for observing minor products, such as highly excited neutral species and anions after the molecular inner-shell excitations. A strong enhancement due to the N^* formation has been observed around the 1s threshold of N_2 molecules. It has been found that the highly excited N_2^<+^*> states leading to the N^* formation are populated by spectator Auger decay from the core-excited states, as well as by the recapture of slow photoelectrons into the Rydberg orbitals. It turns out that the metastable observation is a new and sensitive tool to study the decay dynamics of core-excited states and the photoelectron recapture due to the post-collision interaction. Concerning the anion imaging detection after the molecular inner-shell excitations, we have confronted difficulty in eliminating a large background noise by electrons, which may be fixed by performing time-resolved experiments.