Site-specific photochemistry following soft x-ray irradiation

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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.