Chinese Journal of Nature

Development of large-scale user facilities for photon science in China

LIU Zhi, WAN Weishi, WANG Dong

2024, 46(3): 161-172. doi:10.3969/j.issn.0253-9608.2024.03.001

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Large-scale user facilities for photon science, including synchrotron radiation sources and free-electron lasers, produce high flux, high brightness light with photon energy ranging from infrared to hard X-ray and continuously tunable. As a result, synchrotron radiation sources and free-electron lasers become the centers of scientific research for multiple fields such as physics, chemistry, material science, life sciences, energy, and environmental sciences over the past half a century. In China, synchrotron radiation sources and free-electron lasers have been developed for four decades and state-of-the-art facilities are under construction, making China one of the major powers of these facilities. In this paper, the history and present state of synchrotron radiation sources and free-electron lasers in China are described through introducing the existing and upcoming facilities, with brief discussions on future development.

Advances in extending ultrafast and nonlinear spectroscopy to X-ray wavelengths

LIU Weimin, LI Runze, PENG Peng, DAI Sheng, LI Zhenhui, WANG Han, John Andrew McGuire

2024, 46(3): 173-184. doi:10.3969/j.issn.0253-9608.2024.03.002

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Nonlinear and ultrafast optical (far infrared to near ultraviolet) spectroscopic techniques are versatile tools for probing material dynamics and symmetries. Recent advances in the design of X-ray free electron lasers now allow for the extension of ultrafast spectroscopy to the X-ray region. We discuss the examples of such extensions highlighting the unique contributions that implementation of ultrafast and nonlinear spectroscopy in the X-ray region can make to deepen our understandings of chemical and physical phenomena and material properties.

The application of X-ray free electron lasers in condensed matter physics

WU Yang, WANG Jinghui

2024, 46(3): 185-193. doi:10.3969/j.issn.0253-9608.2024.03.003

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As an emerging experimental method, free electron laser has the characteristics of high power, short pulse, and strong coherence. With wide applications in condensed matter physics research, it has received increasing attentions. In this article we present the research progress of free electron laser in condensed matter physics, especially its importance and potential in magnetism characterization and ultrafast magnetodynamics. We also briefly introduce the research results in phase transition physics and lattice dynamics.

Progress of synchrotron radiation light sources in the field of atomic and molecular physics

DING Bocheng, WU Ruichang, FENG Yunfei, HUANG Jianye, LIAO Jianfeng, JIN Xin, LIU Xiaojing

2024, 46(3): 194-202. doi:10.3969/j.issn.0253-9608.2024.03.004

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Synchrotron radiation is electromagnetic radiation that is emitted along the tangential direction of the motion orbit when electrons make circular or snaking motion at a speed close to the speed of light. It is also called light. This radiation covers a wide band from infrared rays to hard X-rays, and has excellent characteristics such as high brightness and good coherence. Especially in the soft X-ray and hard X-ray bands, synchrotron radiation source is the only source with both high brightness and free choice of wavelength. It provides a highly sophisticated experimental tool for studying the interactions between atoms or molecules and highenergy photons, thus opening a new door to the analysis of the microscopic world. In this paper, the key elements of synchrotron radiation are analyzed in the process of its production and utilization, and the latest progress of synchrotron radiation in atomic and molecular physics is reviewed.

Atomic, molecular and cluster applications of short-wavelength free-electron lasers

DONG Ruichao, FENG Jinze, WANG Xincheng, JIANG Yuhai

2024, 46(3): 203-220. doi:10.3969/j.issn.0253-9608.2024.03.005

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Short-wavelength free-electron lasers provide ultra-intense, ultra-fast, and highly coherent pulse radiation, tunable from extreme ultraviolet (XUV) to hard X-ray regimes, opening up new avenues for studying ultra-fast electron and structural dynamics processes in atoms, molecules, and clusters. From the few-photon single-ionization, few-photon multiple-ionization, and multiphoton multiple-ionization processes induced in atoms to single-pulse imaging of molecular structures and time-resolved molecular dynamics, further to ultra-fast energy and proton transfer processes in clusters, short-wavelength free-electron lasers have a wide range of applications and a number of groundbreaking achievements have successively achieved. The recent research progress of shortwavelength free-electron lasers in the field of atoms, molecules and clusters is systematically reviewed through several illustrative scientific cases. Finally, the current achievements and future development trends of short-wavelength free-electron lasers in this field are summarized and prospected.

Applications of free electron laser in photochemical research areas

ZHU Ruixue, ZHOU Kun, LI Bing, DAI Sheng, WANG Han, WENG Tsu-Chien

2024, 46(3): 221-230. doi:10.3969/j.issn.0253-9608.2024.03.006

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The experimental technology using X-ray free electron laser source (XFEL) has irreplaceable advantages in the research direction of microstructure and electronic structure in the fields of chemistry, biology, materials and other fields. Free electron laser (FEL) sources can emit ultrashort X-ray pulses with pulse durations of 10 fs, making conventional optical lasers ideal for pump-probe experiments. One of its most important applications is the study of ultrafast dynamics inside microstructures (femtosecond pumpprobe measurement). It is a typical technology for studying ultrafast dynamics at very small scales. The rapid developmenting ultrafast X-ray spectroscopy experimental technology has been widely used in different research fields. This article mainly introduces the application and technological development of femtosecond X-ray free electron lasers in the field of photochemistry in recent years. In the future, with the completion of the hard X-ray free electron laser in Shanghai, it can support multi-disciplinary and interdisciplinary fields such as physics, chemistry, energy, materials, environment, etc., and make significant scientific research achievements.

Synchrotron radiation laminography for flat sample system

ZHANG Difei, YAO Yudong, JIANG Huaidong

2024, 46(3): 231-237. doi:10.3969/j.issn.0253-9608.2024.03.007

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Using the characteristics of synchrotron radiation X-ray, such as high penetrability and brightness, non-destructive three-dimensional (3D) imaging of samples significantly impacts the fields including biology, materials science, and chemistry, in conjunction with the iterative reconstruction method. In flat sample systems, conventional iterative reconstruction methods like computed tomography (CT) encounter challenges in imaging size and resolution due to the high-angle missing wedge. Computed laminography (CL) has reintroduced in recent years, addressing the challenge of 3D imaging for flat samples. This paper develops a laminography Fourier iterative algorithm (LFIA) for CL, building upon the existing CT iterative reconstruction algorithm. The LFIA demonstrates superior reconstruction resolution compared to the traditional real-space iterative algorithm, and verifies through simulation and experimentation.

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