物理学报2024，Vol.73Issue(15)：1-8,8.DOI:10.7498/aps.73.20240554
自由电子激光制备高强度亚稳态氦原子和类氦离子
Free electron laser prepared high-intensity metastable helium and helium-like ions
摘要
Abstract
In the precision spectroscopy of few-electron atoms,the generation of high-intensity metastable helium atoms and helium-like ions is crucial for implementing experimental studies as well as a critical factor for improving the signal-to-noise ratio of experimental measurements.With the rapid development of free-electron laser(FEL)and technology,FEL wavelengths extend from hard X-rays to soft X-rays and even vacuum ultraviolet bands.Meanwhile,laser pulses with ultra-fast,ultra-intense and high repetition frequencies are realized,thus making it possible for FEL to prepare single-quantum state atoms/ions with high efficiency.In this work,we propose an experimental method for obtaining high-intensity single-quantum state helium atoms and helium-like ions by using FEL. The preparation efficiency can be calculated by solving the master equation of light-atom interaction.Considering the experimental parameters involved in this work,we predict that the efficiencies of preparing metastable 23S He,Li+and Be2+are about 3%,6%and 2%,respectively.Compared with the common preparation methods such as gas discharge and electron bombardment,a state-of-the-art laser excitation method can not only increase the preparation efficiency,but also reduce the effects of high-energy stray particles such as electrons,ions,and photons generated during discharge.Furthermore,combined with the laser preparation technique,the sophisticated ion confinement technique,which can ensure a long interaction time between the ions and laser,increases the efficiency of metastable Li+and Be2+by several orders of magnitude.Therefore,the preparation of high-intensity metastable helium and helium-like ions can improve the measurement accuracy of precision spectroscopy of atoms and ions.A new experimental method,based on FEL,to study the fine structure energy levels 23P of helium,has the potential to obtain the results with an accuracy exceeding the sub-kHz level.Thus,the high-precision fine structure constants can be determined with the development of high-order quantum electrodynamics theory. In order to measure energy levels with higher accuracy,a new detection technique,which can reduce or even avoid more systematic effects,must be developed.For example,the quantum interference effect,which has been proposed in recent years,seriously affects the accuracy of fine-structure energy levels.If the interference phenomenon of spontaneous radiation between different excited states can be avoided in the detection process,the measurement accuracy will not be affected by this quantum interference effect.High-intensity metastable atoms or ions in chemical reaction dynamics studies also have better chances to investigate reaction mechanisms.In summary,the FEL preparation of high-intensity metastable helium atoms and helium-like ions proposed in this work will lay an important foundation for developing cold atom physics and chemical reaction dynamics.关键词
亚稳态氦原子和类氦离子/精密光谱/自由电子激光/测量信噪比/制备效率Key words
metastable helium and helium-like ions/precision spectroscopy/free electron laser/signal-to-noise ratio/preparation effciency引用本文复制引用
杜小娇,魏龙,孙羽,胡水明..自由电子激光制备高强度亚稳态氦原子和类氦离子[J].物理学报,2024,73(15):1-8,8.基金项目
国家自然科学基金(批准号:12304291,22241301,91736101,12393822)和国家科技部博士后基金(批准号:2022M723062)资助的课题.Project supported by the National Natural Science Foundation of China(Grant Nos.12304291,22241301,91736101,12393822)and the Science Foundation for Postdoctoral Research of the Ministry of Science and Technology of China(Grant No.2022M723062). （批准号:12304291,22241301,91736101,12393822）
