Soft X-Ray Spectroscopic Studies of Mixed Valence 4f Electronic States in Rare Earth Compounds

(1)CeRh_3B_2的三维吸收谱偏振相关性的测量。CeRh_3B_2是一种具有六方晶体结构的铁磁体，由于它具有较高的居里温度，即T_o=112K，因此人们对其进行了大量的研究。根据光电子能谱的结果，它也被称为混合价材料，基态4f电子数n_f=0.85-0.90。CeRh_3B_2中的Ce原子沿c轴形成直链，且Ce-Ce原子间的距离远小于c-面上的距离。因此，平行于和垂直于CeRh_3B_2的六方c轴的偏振方向的Ce-3d X射线吸收谱可能会有所不同。测量于今年4月在KEK-PF举行。(2)用于探测软X射线的平行板雪崩室(PPAC)的新发展。在大块晶体中，用总电子产生法测量了吸收光谱。抛射出的光电子对表面条件非常敏感。另一方面，荧光X射线对于检测块状材料是非常有用的。为了检测荧光X射线，采用了气体流动正比室。为此，设计了低压平行板雪崩室，现已试运行。(3)电子能量损失能谱仪。众所周知，电子能量损失谱(EELS)提供了与软X射线吸收谱(XAS)相同的信息。反射式能量损失光谱仪是固体物理中一种有用的研究工具。到目前为止，已经制作了静电双聚焦能量分析仪，并设计了电子枪和透镜系统。一个项目正在进行中。

(1) Measurement of polarization dependency in Ce 3d absorption spectra of CeRh_3B_2. CeRh_3B_2 is known to be a ferromagnet with a hexagonal crystal structure, and many studies have been carried out on the compounds since it has a high Curie temperature, i. e., T_o =112K. It is also known as a mixed valence material with the number of 4f electrons n_f in the ground state as n_f = 0.85-0.90, from the result of photoemission spectroscopy. The Ce atoms in CeRh_3B_2 form linear chains along the c-axis, and the interatomic Ce-Ce distance in this direction is much smaller than that in the c-plane. So, a difference in the Ce 3d x-ray absorption spectra between polarization parallel and perpendicular to the hexagonal c-axis of CeRh_3B_2 is expected. The measurement is held this April at KEK-PF.(2) New development of parallel plate avalanche chamber (PPAC) for detection of soft x-ray. In the caseo f bulk crystals, the absorption spectra were measured by total electron yield method. The ejected photoelectron is very sensitive to the surface condition. On the other hand, the fluorescent x-ray is very useful to detect the bulk materials. In order to detect the fluorescent x-ray, gas flow proportional chamber is used. For this purpose, the low pressure parallel plate avalanche chamber is designed and now test operated.(3) Electron energy loss spectrometer. It is well known that the electron energy loss spectra (EELS) provide the same information as the soft x-ray absorption spectra (XAS). The reflection type energy loss spectrometer is a useful research tool for use in solid state physics. Until now, the electrostatic double focusing energy analyzer was made and the electron gun and lens systems are designed. A project is in progress.