Investigations on the establishment and applications of pulsed ENDOR

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In the last term of this research project, the main results obtained so far were examined extensively to conclude this research project, especially innovative developments of two pulsed ENDOR methods and their characteristics. We pursued two different approaches, one starting from TM-mode cavity, which is a standard method for CW-ENDOR or TRIPLE spectroscopy, and one from TE-mode cavity, which is widely used for pulsed ESR spectroscopy. First we analyzed characteristics of these cavities, and examined how they could be modified to pulsed ENDOR experiments.It was established that an ENDOR cavity modified from TM-mode exhibits high ENDOR effect compared to the cavity from TE-mode. But it gave low S/N ratio, because of weak microwave pulse power. The weak spin echo after two- or three-pulse sequence(Davis or Mims ENDOR)is one of the severe drawbacks for the applications in the wide variety of fields. In the TE-mode cavity modified for pulse ENDOR, on the other hand, strong spin echoes are expected so that it leads to the problem how much ENDOR effect results in. In spite of the weak echo height, spectrum resolution as well as S/N ratio were found excellent for conventional pulsed ENDOR spectroscopy. The important point for the TE-mode cavityis accomplishment of high radio frequency power around the samples. One of our ideas is employment of Z-coil system, wllich was first experienced in this project. Another idea is proposal of the 90-degree rotated cavity for usual TE-mode, which was also first designed and manufactured.Some deffects or problems which should be reloved in future were pointed out finally for complete establishment of the pulsed ENDOR spectroscopy. Applicable research could not be made satisfactorily partly due to short term of the research project and limited fund.