Study of Nuclear Resonant Bragg Scattering of Synchrotron Radiation and Its Application to Crystallography

同步辐射核共振布拉格散射研究及其在晶体学中的应用

• 批准号: 60460230
• 负责人: KIKUTA Seishi
• 金额: $ 4.67万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1986
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-60460230/
• 关键词: Nuclear resonant scattering; Synchrotron radiation; Multilayered film; メスバウアーγ線

Studies on X-ray scattering and diffraction have been extensively developed with the use of the high intensity synchrotron radiation. However the monochromaticity and the coherency of X-rays used in these studies are nearly the same as those from conventional X-ray tubes. In contrast it is well known that the nuclear resonant Bragg scattered beam is ultrahighly monochromatic and coherent. Such a beam would open new perspectives to various X-ray studies.In this project we aimed at obtaining the beam with a small angular spread and an extremely narrow band width by using the nuclear resonant Bragg scattering of synchrotron radiation. As the scatterer for observing the scattering with a good S/N ratio, it was proposed to fabricate a multilayered film consisting of ^<57>Fe isotope and natural iron layers. The reflectivities of the multilayered films as a function of a glancing angle were computed on the basis of the dynamical theory of diffraction. As a result, it was concluded to design a film of the layer thickness 8 A^^゜ for ^<57>Fe isotops and 12 A^^゜ for natural iron with 100 layer pairs.By alternate deposition in ultrahigh valuum, the multilayerd films were prepared according to the designed values. The fabricated films were characterized by means of the Mossbauer r-Ray scattering apparatus with a ^<57>Co source and a Bragg peak was observed at the expected angular position. The high precision X-ray optical system was constructed for this study at the wiggler beam line in the Photon Factory. The nuclear resonant Bragg scattering was tried to observe with two multilayeted films arranged in the parallel position and a small peak appeared at the expected Bragg angle. The improvement of a quality of the multilayered films is necessary for the further development of the present study.

随着高强度同步辐射的应用，对x射线散射和衍射的研究得到了广泛的发展。然而，在这些研究中使用的x射线的单色性和相干性几乎与传统x射线管相同。相反，众所周知，核共振布拉格散射光束是高度单色和相干的。这样的光束将为各种x射线研究开辟新的视角。在这个项目中，我们的目标是利用同步辐射的核共振布拉格散射获得具有小角扩展和极窄频带宽度的光束。作为观测高信噪比散射的散射体，提出制备由^<57>Fe同位素和天然铁层组成的多层膜。根据衍射动力学理论，计算了多层膜的反射率随反射角的变化规律。因此，得出的结论是设计一层厚度为8 a ^^（^<57>铁同位素）和12 a ^^（天然铁）的膜，具有100层对。通过在超高值条件下交替沉积，制备出符合设计值的多层膜。用^<57>Co源的穆斯堡尔r-射线散射仪对制备的薄膜进行了表征，在期望的角位置观察到布拉格峰。为此，在光子工厂的摆动光束线上构建了高精度的x射线光学系统。将两层多层膜平行排列，观察核共振Bragg散射，在期望的Bragg角处出现一个小峰。提高多层膜的质量是本研究进一步发展的必要条件。