Counting correlation analysis of internal conversion electrons excited by nuclear-resonant synchrotron radiation and its application to surface study

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The aim of this research project is detection of internal-conversion electrons excited by nuclear resonant synchrotron radiation and its application to advanced studies of solid surfaces.The first step of this project was a development of time-resolved electron energy analyzer. We have designed two kind of such spectrometer. One was based on a retarding field analyzer which consists of three stage ellipsoidal mesh grid. The special feature of this analyzer is a wide detection angle most preferable to the very weak electron signal. We have make use of an avalanche phot-diode (APD) to measure electrons. The signal to noise ratio of APD was superior to conventional channel-type electron multiplier by several hundreds. The other type is a hemispherical deflector-type analyzer combined with a specially designed streak-camera. This system is for a angular-resolved measurement with nice time-resolution. Maximum time resolution is 20ps.The measurement of internal-conversion electron was made at NE-3 beamline in KEK.We have successfully measured a tail of electron emission after irradiation of synchrotron radiation. The sample of this measurement was Fe_2BO_<3.> crystal. To elucidate the nature of delayd emission and new surface phenomena, the measurement of delayd electron emission is continued.