少周期飞秒激光场下Ne原子的非顺序双电离  

Nonsequential double ionization of Ne subject to few-cycle femtosecond laser pulses

作　　者：全威[1] 肖智磊[1,2] 陈永菊[1,2] 许松坡 赖炫扬[1] 华林强[1] 龚成[1] 陈京[3] 柳晓军[1] QUAN Wei XIAO ZhiLei CHEN YongJu XU SongPo LAI XuanYang HUA LinQiang GONG Cheng CHEN Jing LIU XiaoJun(State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China University of Chinese Academy of Sciences, Beijing 100080, China Institute of Applied Physics and Computational Mathematics, Beijing 100088, China)

机构地区：[1]中国科学院武汉物理与数学研究所,波谱与原子分子物理国家重点实验室,武汉430071 [2]中国科学院大学,北京100080 [3]北京应用物理与计算数学研究所,北京100088

出　　处：《中国科学：物理学、力学、天文学》2017年第3期56-63,共8页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:11274050;11204356;11334009;11374329;11425414;11474321);国家重点基础研究发展计划(编号:2013CB922201);中国科学院青年创新促进会(编号:2011242)资助项目

摘　　要：本文实验测量了少周期飞秒激光场下惰性气体Ne原子非顺序双电离引起的Ne^(2+)离子动量分布,发现该分布强烈依赖于激光场的载波-包络相位(Carrier-Envelope Phase,CEP),在某些CEP条件下呈现出明显不对称的双峰结构.半经典理论计算可以定性地重现实验结果.理论分析表明,二价离子的不对称动量分布来自于非顺序双电离过程中碰撞直接电离(Recollision-Impact-Ionization,RII)与碰撞-激发电离(Recollision-Excitation and Subsequent Ionization,RESI)两个通道的贡献,其中不对称双峰结构来自于RII通道,而RESI通道影响的是低动量部分,导致双峰结构变平.RII通道中产生的Ne^(2+)离子动量分布对CEP有较强的依赖性,而RESI通道中Ne^(2+)离子动量分布随CEP的变化不明显.进一步的计算表明,离子实库仑势在非顺序双电离过程中起到非常重要的作用,它将引起RESI通道产量增大.We investigate experimentally and theoretically the evolution of Ne2＋ ion momentum distributions from Nonsequential Double Ionization （NSDI） in few-cycle laser pulses with respect to the Carrier Envelope Phase （CEP）. The distributions depend strongly on the CEP and exhibit an asymmetric double-hump structure at some CEPs. A semiclassical calculation can reproduce the experimental observations qualitatively, where the rescattering scenario is identified as the main mechanism of double ionization. Analysis based on this semiclassical model reveals that double ionization happens a little later than the collision. Depending on the time difference between the ionization moment and the collision moment, we can distinguish two ionization pathways involved, i.e., Recollision Impact Ionization （R/I） （with time difference below 0.1 optical cycle） and Recollision-Excitation and Subsequent Ionization （RESI） （with time difference above 0.1 optical cycle） pathways. The asymmetric pattern results from both RII and RESI： R/I leads to the asymmetric double-hump structure, while RESI contributes to the low momentum part and makes the dip of the double-hump structure shallower. Furthermore, Ne2＋ ion momentum distributions from RII depend strongly on the CEP and the distributions from RESI seem to be not very sensitive to the CEE To shed more light on physical mechanism of the asymmetric momentum distribution, the momentum distributions from two ionized electrons are presented at the collision moment, the ionization moment and the moment right after laser field ends for each pathway, respectively. The comparison unravels that the asymmetry comes from the asymmetric acceleration from the laser electric field after the double ionization moments. To demonstrate the significant role of long range Coulomb potential in NSDI process, we replace the Coulomb potential with a short-range model potential in the calculation and the results show appreciable distinctions from the case of Coulomb potential. It is clar

关 键 词：少周期飞秒激光场 惰性气体原子 载波.包络相位 非顺序双电离 

分 类 号：O562.4[理学—原子与分子物理]