Site-specific photochemistry following soft x-ray irradiation

软X射线吸收在涉及核电子电离的分子中通常会导致分子碎裂。碎裂经常被观察到发生在原子的核心电子激发发生的位置周围。基于这些观察，人们可以考虑使用可调谐的软X射线来刺激化学反应或选择性地破坏大分子有机分子。从这个角度出发，我们设计并建造了一个新的实验装置，包括俄歇电子分析器、阈值电子分析器和质谱仪，以阐明吸附在表面的分子的软X射线光化学的完整机制。利用该装置，我们成功地探测到了氧/铜体系中光激脱附的俄歇电子和离子产物。我们还发现，无论激发能是低于还是高于核心电子的电离极限，软X射线辐照后的碎裂模式都会发生变化。

Soft x ray absorption in a molecule involving ionization of a core electron usually results in a fragmentation of molecule. The fragmentation has often been observed to occur specifically around the site of the atom where the core electron excitation takes place. Based on these observations one might consider the use of tunable soft x rays to stimulate chemical reactions or to selectively break large organic molecules, as one pleases.From this point of view, in this project we have designed and constructed a new experimental apparatus involving an Auger electron analyser, a threshold electron analyser, and a mass spectrometer to elucidate the full mechanism of a soft x ray photochemistry of the adsorbed molecules on the surfaces. Using this apparatus, we have succeeded in detecting both Auger electrons and ionic products of photo-stimulated desorption in a oxygen/Cu system. We have also found that the fragmentation pattern following soft x ray irradiation changes whether the exctation energy is lower or higher than the ionization limit of a core electron.