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中国物理学会期刊

高电荷态离子阿秒激光光谱研究展望

CSTR: 32037.14.aps.72.20230986

Prospect for attosecond laser spectra of highly charged ions

CSTR: 32037.14.aps.72.20230986
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  • 高电荷态离子(highly charged ions, HCI)的光谱测量不仅可以检验量子电动力学效应和相对论效应等基本物理模型, 还能够为天体物理、聚变等离子体物理甚至HCI光钟等研究提供关键原子物理数据. HCI离子能级跃迁大多在极紫外甚至X射线波段, 受限于目前的光源技术较难直接产生该波段激光, 实验室对于HCI离子的激光光谱测量十分有限. 阿秒光源具有极紫外甚至软X波段的高光子能量和超短的脉冲持续时间, 为实验室开展HCI的光谱测量与超短能级寿命研究等提供了新的机遇. 本文分析了目前国际上利用同步辐射光、自由电子激光以及飞秒高次谐波等光源已开展的一些HCI离子光谱实验测量的基本方法、研究进展等, 总结了阿秒光源、离子靶等技术的研究现状, 讨论了将极紫外阿秒光源与不同HCI离子靶的技术结合开展HCI离子阿秒时间分辨激光光谱测量的可行性, 并提出了一个HCI离子阿秒光谱测量的初步设计方案, 为未来开展HCI光谱精密测量与离子能级寿命测量等研究提供参考.

     

    The spectra of highly charged ions (HCIs) are of great significance for astronomical observation, astrophysical model establishment, and test of quantum electrodynamics (QED) theory. However, the transitions of HCI are mostly in the extreme ultraviolet or even X-ray range, the excitation spectra of HCI measured by laser spectroscopy in laboratory are very limited due to lack of the suitable light source. Up to now, only few experiments on the spectra of HCIs performed on synchrotron radiation, free electron laser or heavy-ions storage ring have been reported, which are summarized in this work. With the development of attosecond technology, several attosecond light source facilities have been built, such as extreme light infrastructure attosecond light pulse source (ELI-ALPS) and synergetic extreme condition user facility (SECUF), which have high photon energy and ultra-short pulse duration in the extreme ultraviolet and even soft X-ray range, providing new opportunities for laboratory research on HCI spectra and ultra short energy level lifetimes. Electron beam ion trap (EBIT), electron cyclotron resonance (ECR), and heavy-ion storage ring are usually used to generate ion target. But it is difficult to combine the attosecond laser source with large scale facility of HCI, for none of laboratories has both these two facilities now. Thus, two possible experimental schemes for attosecond spectrum of HCIs are proposed in this work. One scheme is that an EBIT can be designed as a terminal of attosecond laser facility, such as ELI-ALPS and SECUF, which can output different laser beams with high photon energy, ultra-short pulse duration or high flux. Another scheme is that a table-top HHG system pumped by an all-solid-state femtosecond laser or fiber femtosecond laser with high power can be combined with heavy-ion storage ring, such as ESR, CSRe, HIAF, and FAIR. Owing to high energy of ions in storage ring, the measurable energy levels of HCIs can even be extended to keV by the Doppler shift. Three different measurement methods: fluorescence detection, ion detection and attosecond absorption spectroscopy, can be used to obtain the HCI spectrum. Finally, a preliminary experimental setup for attosecond laser spectrum of HCI is proposed. The proposal on combining extreme ultraviolet attosecond light source with HCI target is discussed, and the feasibility of attosecond time-resolved precision spectrum for HCI is analyzed according to the typical parameters of attosecond light source and the known excitation cross-section and detection efficiency, which can provide a new platform for implementing ion level structure calculation, QED theory high-precision test and astronomical spectroscopic observation. It can be used to measure the ultra-short lifetime, low excitation cross-section ionic energy level, and even some transitions with large energy interval. We hope that this work can provide a reference for the experimental measuring of HCI spectrum and ion energy level lifetime in future.

     

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