Dynamics of ^<57>Fe atoms in Graphite compounds by means of in-beam Mossbauer Spectroscopy

放射性同位素束流作为核反应后产生的二次束流，在材料科学领域受到越来越多的关注，因为一些加速器设施的束流强度和束流注入能量都有了很大的提高。因此，放射性同位素不仅可以作为植入后立即获得材料原子信息的核探针，而且可以作为改变材料物理和化学性质的工具。光束内^<57>Fe穆斯堡尔光谱装置是RIKEN加速器研究设施新开发的。与AVF回旋加速器相连的装置可用于束流实验，其中2-4 MeV/核子的束流能量足以激发穆斯堡尔能级，例如，库仑激发和反冲注入产生的^<57>Fe的14.4 keV能级。本文利用光束内穆斯堡尔光谱研究了范德华固体（固体稀有气体、多晶石墨和单晶石墨）样品中^<57>铁探针原子的占位、化学状态和动力学。

A radioactive-isotope beam (RI beam), which is produced as a secondary beam after a nuclear reaction, is becoming more and more attractive in materials science, because the beam intensity and the beam energy available for implantation have been considerably increased at some accelerator facilities. Accordingly, the radioactive isotopes can be used not only as nuclear probes to obtain atomistic information in materials immediately after the implantation, but also as a tool to change the physical and chemical properties of materials.The setup for in-beam ^<57>Fe Mossbauer spectroscopy is newly developed at RIKEN Accelerator Research Facility. This set-up connected to the AVF cyclotron can be used for in-beam experiments, where the beam energy of 2-4 MeV/nucleon is sufficient for the excitation of the Mossbauer level, for instance, the 14.4 keV level of ^<57>Fe produced by the Coulomb excitation and recoil-implantation. The identification of site-occupation, chemical states, and dynamics of ^<57>Fe probe atoms in the samples of van der Waals solids (solid rare-gases, polycrystalline graphite, and single-crystal graphite) have been studied by means of the in-beam Mossbauer spectroscopy.