A development of absorption spectra for wide energy region by inelastic x-ray scattering

吸收系数、反射率等光学性质不仅是物质最基本的性质之一，而且还与介电常数、范德华力等其他性质有关。特别是，只要在较宽的能量范围内已知，材料与x射线和带电粒子的相互作用也可以用光学数据来描述。然而，由于各种实验困难，在真空-紫外和软x射线区域的光学常数的测量很少，而且实际上不存在关于液体的光学常数的测量。本课题试图建立一种新的光谱方法，利用硬x射线的非弹性散射来获得各种液体的宽能区光谱。利用目前的援助资金，一个具有多功能性的新光谱仪已经建成，并被送往同步辐射设施（筑波光子工厂和美国布鲁克海文国家同步加速器光源）。在那里进行了测量，我们成功地获得了包括水在内的几种液体在0 ~ 200 eV之间的非弹性x射线散射光谱，该光谱可以转换为真空紫外区的光学常数。关于水的数据是辐射化学的基础，一篇评论论文已经发表在《日本辐射化学学会杂志》上。此外，从非弹性x射线散射谱的动量转移依赖关系也可以推导出x射线结构因子，它与电子关联密切相关。用组态相互作用法和新发展的耦合聚类法对结果进行了分析。

Optical properties such as absorption coefficient and reflectivity are no only one of the most fundamental properties of matters but also are related to other properties like dielectric constants and van der Waals force. In particular, interactions of the material with x-rays and charged particles are also described by optical data, as long as they are known over wide energy range. Because of various experimental difficulties however, measurements of optical constants in the vacuum-uv and soft x-ray region are scarce, and are practically nonexistence about liquids. In this project an attempt is made to establish a new spectroscopic method that makes it possible to obtain spectra of various liquids over wide energy region by the use of inelastic scattering of hard x-rays.A new spectrometer which features versatility has been constructed with the present grant-in-aid, and it was sent to synchrotron radiation facilities (Photon Factory at Tsukuba and National Synchrotron Light Source at Brookhaven, U.S.A.). Measurements were carried out there and we have succeeded in obtaining inelastic x-ray scattering spectra of several liquids including water between 0 and 200 eV, which can be transformed to optical constants in the vacuum uv region. The data on water makes a basis of radiation chemistry, and a review paper has been written to the Journal of Japanese Radiation Chemistry Society.In addition, x-ray structure factor can also be deduced from momentum-transfer dependence of inelastic x-ray scattering spectra, which is closely related with electron correlation. The results have been analyzed in terms of the configuration interaction method as well as newly developed coupled cluster method.