Vacuum Ultraviolet Emission Spectra of Organic Photoconductors Excited by Low Energy Electrons.

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This work, the object of which is to observe directly the electronic structure of unoccupied levels in organic photoconductors, has been carried out for these two years, since those levels are even less studied experimentally than valence levels in spite of their importance in relation to physical and chemical properties.The main program of this work is to make an instrument for the measurement of vacuum ultraviolet light emitted in accordance with electronic relaxations to low unoccupied levels in a sample solid or thin film irradiated with low energy electrons in vacuo. We designed such an ultra-high vacuum compatible instrument consisting of a measurement chamber, a system for lodging an electron gun, a light detection system, a sample transfer system and a sample preparation chamber, through examinations of various aspects from measurement principles to practical processing of machineries, and reached a final stage to assemble the instrument at the end of the last fiscal year.In th … More is fiscal year we continued to adjust respective parts of the instrument. A severe problem which could not been foreseen at the stage of planning was found on a high-intensity low-energy electron gun designed with improving a Johnson-type one considerably, so that the parts of significance have been reproduced. Further, we have improved a light focusing system and a sensitizer at the first anode of the detector to increase the sensitivity for vacuum ultraviolet lights. With taking account of advices of researchers at the Institute for Solid State Physics, the University of Kyoto. On the other hand, ultra-high vacuum of the instrument was broken accidentally, when a sample cooling system, aimed to diminish a radiation damage by electron irradiation on an organic sample, was being troubleshooted. As every trial to trace the origin of the leak was failed, the instrument was returned to manufactory located at Osaka, and it was found that the main valve of the preparation chamber had been out of order. While its substitute was ordered (abroad), the earthquake attacked the southern area of the Hyogo Prefecture and damaged our instrument, which needed an overhaul. However, its reconstruction has almost been completed at the end of this fiscal year.Thus, the direct observation of unoccupied levels in organic photoconductors, included in the first plan of this project, has not yet been started. Nevertheless, the instrument to be useful for this purpose has almost been completed by the financial support of this Grant-in-Aid. We will make the most of it to studies of organic solid state chemistry. Less