Study on the electronic states of the outermost surface layers by Metastable deexcitation spectroscopy.

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The purpose of this project is to construct a machine for metastdble deexcitation spectroscopy and to measure the outermost surface electronic structures using MDS. We constructed a beam source for MDS and it combined with a UHV chamber which was already working. We adopted a supersonic nozzle beam of He as the metastable atom source. The high-pressure gases are expanded through a nozzle into vacuum. The expanded stream is skimmed by a skimmer located at 10mm downstream to form an atomic beam. Therefore, we need two pumping stages in parallel for evacuation of introduced gases. Two big oil diffusion pumps combined with a box type vacuum chamber which is made of aliminium alloy. We found that an another UHV chamber was required for reducing the contamination of the sample held in the UHV main chamber. Combining the small UHV chamber which is pumped by a turbomolecular pump, we settled the problem. Owing to darkness of an energy analzyer which was already set in the main chamber, it was unsuccessful to get a MDS spectrum. We are now preparing a new type of analyzer with high-brightness.