Production and decay of K-shell hollow atoms in relativistic ion-atom collisions

by Prof. Caojie Shao（邵曹杰） (Institute of Modern Physics, Chinese Academy of Sciences)

Wednesday 15 Oct 2025, 12:00 → 13:30 Asia/Shanghai

5#/6th-603 - Meeting Room 603 (Science Building)

Abstract:

K-shell hollow atoms—atoms with both K-shell electrons removed while the outer shells remain occupied—are very special atomic species that exist under highly nonequilibrium conditions. Heavy hollow atoms provide a unique opportunity to study angular momentum coupling and electron-electron correlation in an exotic regime, where the Breit interaction and relativistic effects play a more prominent role than in light atoms. In addition to their significance for fundamental atomic physics, the production mechanisms and decay properties of such atoms are also important for research on high-energy-density plasmas, hard X-ray lasers, and nuclear physics. Theoretical studies on K-shell hollow atoms began as early as the 1930s. However, due to the challenges in producing such atoms, experimental observations were not made until the 1970s, when Briand and colleagues first indirectly detected X-rays emitted from hollow Ga atoms produced by a ⁷¹Ge radioactive nuclear. Since then, a variety of beam sources—including radioactive sources, electrons and HCIs, and photons—have been employed to ​produce​ K-shell hollow atoms and investigate their decay properties. This report will present an overview of research on K-shell hollow atoms and introduce the latest experimental results on X-ray spectroscopy of high-Z hollow atoms at the HIRFL-CSR (Heavy Ion Research Facility in Lanzhou – Cooling Storage Ring).

Biography:

​Prof. Caojie Shao, Associate Research Fellow and Deputy Director of the Highly Charged Ion Precision Spectroscopy Group at the Institute of Modern Physics, Chinese Academy of Sciences. He received his Ph.D. in Particle Physics and Nuclear Physics from the University of Chinese Academy of Sciences (UCAS) and Lanzhou University in 2017. His primary research focuses on X-ray spectroscopy experiments involving highly charged ions (HCIs) conducted at heavy-ion storage rings. This work aims to investigate radiative electron capture (REC), multiple ionization and excitation mechanisms that occur during particle-atom collisions, as well as exotic decay modes (such as hypersatellite transitions and two-electron one-photon [TEOP] transitions).​

Host: Prof. Ke Han

Alternative online link：https://meeting.tencent.com/dm/n7U9cXi6Z2tP

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