桌面飞秒极紫外光原子超快动力学实验装置  

A tabletop experimental system for investigating ultrafast atomic dynamics based on femtosecond extreme ultraviolet photons

作　　者：海帮 张少锋[1] 张敏[1,2] 董达谱 雷建廷 赵冬梅 马新文[1] Hai Bang;Zhang Shao-Feng;Zhang Min;Dong Da-Pu;Lei Jian-Ting;Zhao Dong-Mei;Ma Xin-Wen(Institute of Modern Physics,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Nuclear Science and Technology,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]中国科学院近代物理研究所,兰州730000 [2]中国科学院大学,北京100049 [3]兰州大学核科学技术学院,兰州730000

出　　处：《物理学报》2020年第23期146-153,共8页Acta Physica Sinica

基　　金：国家重点基础研究发展计划(批准号:2017YFA0402300);国家自然科学基金(批准号:11934004)资助的课题.

摘　　要：飞秒极紫外光脉冲是研究原子分子超快动力学过程的重要工具,是同步辐射及自由电子激光这样的大科学装置的重要补充,而且具有非常诱人的发展前景.本工作基于大功率飞秒近红外激光在气体介质中的高次谐波过程,搭建了一套桌面飞秒极紫外光源.使用充气的中空波导管产生高次谐波,增大了驱动光与介质的作用长度,显著提高了光子产额.使用了光栅的圆锥衍射模式来实现高次谐波光子能量的选择,在保证高衍射效率的同时,减小了光栅衍射对于光脉冲的时间展宽效应.通过实际测量,光源的输出光子能量可覆盖20-90 eV的范围.在光子能量为40 eV附近,输出光子流强达1×10^10 photons/s,光子能量分辨约为0.4 eV.该光源结合新研制的反应显微成像谱仪,为研究极紫外光与原子分子的相互作用提供了独特的手段.目前已成功开展多次原子及分子电离实验,系统性能稳定.Femtosecond extreme ultraviolet(XUV)light pulses play an important role in investigating the ultrafast dynamics of atoms and molecules,and are complementary to the conventional large facilities like synchrotron radiation and free electron laser.We build a table-top femtosecond extreme ultraviolet light source based on the high-order harmonic generation(HHG)process of gaseous medium in a strong laser field.We implement HHG by focusing an intense IR laser into a 5 cm long gas-filled hollow waveguide,instead of the conventional tightly focusing geometry with gas jet.Inside the waveguide,the laser peak intensity is nearly constant and the gas pressure is well-controlled,making it possible to maintain the phase matching condition over an extended distance.And a fully coherent high harmonic beam builds up along the waveguide,leading to a dramatically higher HHG efficiency.Monochromatic XUV light pulses are obtained by spectral selection of the HHG through employing the conical diffraction method of grating.With this geometry used,the pulse broadening caused by wave front tilting during the diffraction can be strongly suppressed,especially for the case of grazing incidence.And the femtosecond temporal character of the light pulse can be preserved while keeping a high reflectivity.The temporal broadening of the XUV light pulse in our setup is estimated to be within 100 femtosecond.By using different noble gases,photons with energy values ranging from 20 eV to 90 eV are produced.For the 27thorder harmonic centered at 41.9 eV,the flux is measured to be 1×10^10 photons per second,with an energy spread of 0.4 eV.In order to investigate the ultrafast dynamic behaviors of gaseous atoms and molecules with an HHG-based XUV source,we develop a reaction microscope with ultrahigh vacuum of about 10-11 mbar.The combination of HHG-based XUV with the newly developed reaction microscope provides a unique tool for studying the XUV photon and atom/molecule interaction.A series of experiments has been successfully carried out on the plat

关 键 词：极紫外光源 高次谐波 圆锥衍射 反应显微成像谱仪 

分 类 号：O56[理学—原子与分子物理] TN23[理学—物理]