STUDY OF THE ELECTRONIC STATE OF THE MANGANESE CLUSTER IN PHOTOSYSTEM II : AN APPROACH BY SOFT X-RAY EMISSION SPECTROSCOPY

点击翻译按钮获取中文摘要

The purpose of this study was to perform Mn 2p soft x-ray absorption/emission measurement of the oxygen evolving complex, manganese cluster, in photosystem II. In order to apply soft x-ray absorption/emission measurement which is limited to a solid system or gas system, to a system in solution, we have improved the following three points:1.Development of the soft X-ray emission spectrometer --balancing high energy resolution and high detection efficiency--It has become possible to measure the soft x-ray emission from a monolayer adsorbed on a substrate in only 30 minites, with the energy resolution of 1000(E/ΔE).2.Development of a solution cell with Si_3N_4 membrane to hold a solution in an ultra high vacuumWe have succeeded to maintain about 2μl solution sample between two Si plates with Si3N4 thin films of 200nm thickness using a sealant compatible for ultra high vacuum.We used this cell to measure Fe 2p soft x-ray absorption and emission measurement of a stable and dense (-10mM) myoglobin.3.Development of a sample scanning system to reduce radiation damageWe have developed a sample scanning system using the solution cell. However, an opening area toward soft x-rays required for control of a sample position and the opening area restricted for a vacuum-proof did not suit well, so we have given up the scanning of the sample position during measurements. Instead, we have developed a bulk sensitive spectrometer, a high energy photoemission spectrometer, to place a solution sample in a low vacuum.