He原子高阶阈上电离的空间类共振增强结构  

Spatial Resonance-like Enhancements in High-order above Threshold Ionization of Helium

作　　者：周又洋 王怡昕 胡梦竹 贾欣燕 ZHOU You-yang;Wang Yi-xin;HU Meng-zhu;JIA Xin-yan(School of Physical Science and Technology,Southwest Jiaotong University,Chengdu 610000,China)

机构地区：[1]西南交通大学物理科学与技术学院,四川成都610000

出　　处：《量子光学学报》2023年第3期29-36,共8页Journal of Quantum Optics

摘　　要：利用量子S-矩阵理论,研究了光电子末动量沿着强激光场的极化方向,以及与场方向存在一定夹角时,He原子高阶阈上电离光电子能谱的类共振增强结构。研究发现:光电子末动量不论是沿着场的极化方向还是与场的极化方向存在一定夹角时,均会出现类共振增强结构,且该结构出现的光强满足通道关闭(channel closing,CC)条件,从而证实了空间类共振增强结构的通道关闭机制。同时,结果表明在光强一定时,随着光电子出射角度的不断增加,类共振增强结构会逐渐向低能量方向移动;而当光电子出射角度不变时,随着光强的不断增加,类共振增强和抑制现象会交替出现在光电子能谱中,造成这些现象的可能原因是返回次数不同的量子轨道之间的相干叠加。进一步分析发现,在光电子末动量与场的极化方向存在一定夹角时,也会出现类似于沿着场方向的type-Ⅰ和type-Ⅱ两种类共振增强结构。Within the framework of the strong-field approximation theory,using the quantum S-matrix theory and the saddle point method,we investigated the resonance-like enhancement structures in the high-order above-threshold ionization photoionization electron energy spectrum of He atoms,when the final momentum of photoelectrons was aligned along the direction of the strong laser field and at an angle to the field direction.The research results indicate that the resonance-like enhancement structures appeared regardless of whether the final momentum of photoelectrons was aligned along the polarization direction of the field or at an angle to it,and the intensities of the enhancement peaks also satisfied the channel closing conditions,further confirming the channel closing mechanism of resonancelike enhancement.At the same time,it was found that with the increase in laser intensity,the resonance-like enhancement and suppression phenomena alternated in the photoelectron energy spectrum.When the laser intensity was constant,the resonance-like enhancement structures gradually shifted towards the low-energy direction as the emission angle of photoelectrons increased.These phenomena may be caused by the interference of quantum orbitals with different return times.To further analyze these resonance-like enhancement structures,the photoelectron energy spectrum was calculated for photoelectron emission angles of 0°,10°,and 20°,laser intensities ranging from 1.5 × 10~(14)W/cm~2 to 2.5 × 10~(14)W/cm~2,and photoelectron kinetic energy ranging from 2 a.u.to 4.5 a.u.Two types of island structures were observed in the photoelectron energy spectra:Island Ⅰ,with the enhancement structures concentrated in the central region of the channel closing laser intensity,while Island Ⅱ and Island Ⅱ',with the enhancement structures distributed within a certain range of the channel closing laser intensity.Similar Island Ⅰ,Island Ⅱ,and Island Ⅱ' enhancement structures were obtained for photoelectron emission angles of 10° and 20° as

关 键 词：强激光场 阈上电离 类共振增强 

分 类 号：O562[理学—原子与分子物理]