摘要
对阈上电离过程中电子电离时间特性的研究,不仅是理解强场非微扰量子动力学的关键,也是当前阿秒科学重点关注的问题之一。本文基于长度规范下的量子S-矩阵理论,利用类维格纳分布函数方法,对氢原子在四个光学周期线偏振激光脉冲中(载波包络相位(carrier-envelope phase,CEP)φ=0和φ=π/2两种情况)的阈上电离动力学行为进行了系统研究。重点分析了沿不同出射方向电离电子的时间-能量分布、能谱特性以及瞬时电离率分布,研究发现这些分布特性对载波包络相位和电子出射方向具有显著依赖性。时间-能量分布方面:当CEPφ=0(φ=π/2)时,t~1.75 o.c.(optical cycle)和t~2.25 o.c.(t~1.5 o.c.、2.0 o.c.、2.5 o.c.)处电离条纹的分布形态,以及t~2.0 o.c.(t~1.75 o.c.和t~2.25 o.c.)处干涉结构的数量和能量间隔均随出射角Θ而变化。能谱特性方面:光电子能谱峰的能量间隔随出射角Θ变化,仅在横向出射方向(Θ=90°)呈现规则的2ω间隔;与CEPφ=0相比,φ=π/2时的能谱峰结构对比度显著降低。瞬时电离率分布方面:两种CEP条件下分布呈现不同的对称性特征,且电离峰值对应时间会随出射角Θ变化而发生偏移。这些特征主要源于激光场接近极值时刻发射电子间的干涉效应,本研究为深入理解强场阈上电离过程中的量子干涉现象提供了新的理论视角。
Objective Investigation of time-dependent characteristics in above-threshold ionization(ATI)is not only crucial for understanding strong-field nonperturbative quantum dynamics,but also represents one of the key research focuses in attosecond science.This work systematically examines the time-energy characteristics of atomic ATI in linearly polarized intense laser fields.While existing studies have primarily focused on electrons emitted along the laser polarization direction and the direction perpendicular to it,our research provides a comprehensive analysis the time-energy properties of electrons ejected in all directions.These findings significantly advance our understanding of electron dynamics in strong-field ionization processes and offer novel theoretical insights for attosecond science research.Methods Within the framework of quantum S-matrix theory in length gauge,this study employs the Wignerdistribution-like(WDL)method to calculate the time-energy distributions,spectral characteristics,and timedependent ionization rates of photoelectrons emitted along various directions from hydrogen atoms subjected to a four-cycle linearly polarized laser field with two distinct carrier-envelope phases(CEP)φ=0和φ=π/2.Results and Discussions The time-energy distributions reveal that for both CEPφ=0 andCEPφ=0 cases,the morphological characteristics of ionization stripes observed at t~1.75 o.c.and t~2.25 o.c.(or at t~1.5 o.c.,2.0 o.c.,2.5 o.c.forφ=π/2)demonstrate significant dependence on the emission angle,as do the number of interference structures and their energy spacings at t~2.0 o.c.(or at t~1.75 o.c.and t~2.25 o.c.forφ=π/2).The spectral analysis shows that while the energy spacing between photoelectron peaks varies with emission angle,only the transverse emission direction(Θ=90°)exhibits the characteristic regular 2ω spacing,with theβ=π/2 case showing markedly reduced peak contrast compared to φ=0.The time-dependent ionization rate distributions display distinct symmetry properties under different CEP conditions,where the timing of ionization peaks shifts systematically with emission angle.These observed phenomena primarily arise from quantum interference effects occuring between electrons emitted near the extremal points of the laser field cycle.Conclusions The study reveals that in hydrogen atoms subjected to four-optical-cycle linearly polarized laser fields,the time-energy distributions,spectral characteristics,and time-dependent ionization rates of emitted electrons exhibit significant dependence on both the carrier-envelope phase and electron emission angles.Through comprehensive analysis of electron dynamics in all emission directions,this research provides new theoretical insights into quantum interference phenomena in strong-field above-threshold ionization processes.Thereby offering valuable theoretical references for related experimental investigations.
作者
胡梦竹
樊代和
贾欣燕
HU Meng-zhu;FAN Dai-he;JIA Xin-yan(School of Physical Science and Technology,Southwest Jiaotong University,Chengdu 610000,China)
出处
《量子光学学报》
北大核心
2025年第2期85-94,共10页
Journal of Quantum Optics
基金
国家自然科学基金(62374139)。
关键词
强激光场
阈上电离
时间-能量分布
类维格纳分布函数
intense laser field
above-threshold ionization
time-energy distribution
Wigner-distribution-like function
