Studies on relaxation processes of core-excited molecules followed by deformation

分子软x射线光谱学是近二十年来研究分子核电子激发后的衰变动力学和分子核电子电离动力学的一个重要热点，它与核激发分子的弛豫动力学有关。众所周知，多重符合技术是研究岩心孔形成后状态到状态解离动力学的有力工具。然而，以前为这类研究而研制的许多实验仪器都有一定的应用局限性，因此并不令人满意。这里开发的新设备是世界著名的EPICEA II的自然扩展，在法国奥赛的LURE开发，通过引入两个二维探测器，对电子和离子探测都具有足够快的响应。为了满足测定电子或离子初始动量的空间聚焦条件，设计了一种新型的双环形静电分析仪。在UVSOR设施新建的光束线BL4B上进行的分析仪性能测试结果清楚地表明，即使是简单的电子能谱，也迫切需要进一步改进。最近在LURE使用与我们相似的概念开发的新设备获得的结果，直接显示了H2O和CO2中核心激发态的分子几何变形的重要作用，它诱导了特定的破碎通道。这种工作正是我们在现有的实验装置发展之后想要做的，并为我们未来系统的改进提供了动力。在不久的将来，我们将研制一种新的飞行时间质谱仪，并将其引入我们的实验装置。

This work intends to cover an important and hot topic in the research field of molecular soft X-ray spectroscopy, in which the decay dynamics following core-electron excitation as well as core-electron ionization for molecules has been extensively studied over the past two decades, which is related to the relaxation dynamics of core-excited molecules. As is widely recognized, the multi-coincidence technique is a powerful tool to investigate state-to-state dissociation dynamics following the core-hole creation. However, many experimental apparatuses previously developed for such investigations were not so close to satisfaction, because each of them has a certain limitation for its application. The new apparatus developed here is a natural enlargement of the capability of the world-famous EPICEA II developed at LURE, Orsay, France, by introducing two two-dimensional detectors with sufficiently fast response, both to electron and ion detections. A great deal of effort has been put into designing a new electrostatic analyzer with a double toroidal shape, in order to satisfy spatial focusing condition for determining the initial momenta of electrons or ions. The result of the performance tests for the analyzer performed at a newly constructed beamline BL4B of the UVSOR facility clearly indicate that further improvements are strongly desired even for the simple electron spectroscopy. The recent results obtained at LURE using a new apparatus developed with the similar concepts as we have, show directly the significant role of the molecular geometry deformation of the core-excited states in H2O and CO2, which induces to specific fragmentation channels. This kind of work is exactly what we would like to perform after the development of the present experimental setup, and gives us an impetus for future improvement of our system. A new time-of-flight mass spectrometer with a two-dimensional detector will be developed and introduced to our experimental setup in the near future.