Non-sequential double ionization of argon in counterrotating circularly polarized two-color laser fields
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摘要: 在经典系综模型下, 研究了氩(Argon, Ar)原子在800 nm和400 nm反向旋转圆偏振双色(Counterrotating Circularly Polarized Two-Color, CRTC)激光场驱动下的非顺序双电离(Non-Sequential Double Ionization, NSDI)过程. 理论分析了激光强度、双色场强度比、脉冲相对相位, 以及激光脉冲宽度等光场参数对非顺序双电离机制及其量子产率的影响, 得到了双电子能量的时间演化谱; 发现并分析了两种不同的非顺序双电离机制; 讨论了电子返回碰撞能对不同非顺序双电离过程的影响.Abstract: In this paper, the non-sequential double ionization (NSDI) process of Ar in 800 nm and 400 nm counterrotating circularly polarized two-color(CRTC) laser fields was studied using the classical ensemble model. The dependence of the non-sequential double ionization mechanism and quantum yield on laser intensity, laser intensity ratio, relative phase, and pulse duration of two pulses is calculated and analyzed in detail. The energy evolution of two electrons in the time domain is obtained and two different non-sequential double ionization mechanisms are revealed. The influence of the electron collision energy for different non-sequential double ionization processes is also discussed.
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图 1 Ar原子在单色圆偏振场(绿色空心菱形)和4种不同的CRTC激光场中的双电离产率,
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ 分别为 0.5, 1, 2, 6; 阴影区域表示电离增强区, 绿色实线所在光场强度为0.4 PW/cm2Fig. 1 Double ionization yields of argon atoms in monochromatic circularly polarized fields (olive-colored hollow diamond) with four different CRTC laser fields. The
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ values are 0.5, 1, 2, and 6, respectively.The shaded area represents the NSDI enhancement zone, the solid green line represents a laser intensity of 0.4 PW/cm2图 2 图中光场强度均为0.4 PW/cm2: (a)、(b)在不同脉宽下, Ar原子双电离几率随
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ 的变化曲线; (c)Ar原子双电离几率随激光脉宽的变化曲线,${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ = 2; (d)不同脉宽下双电离几率随相对相位的变化曲线,${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ = 2Fig. 2 The laser intensities in the four figures are all 0.4 PW/cm2: (a), (b) Double ionization probability as a function of
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ at different pulse widths; (c) Double ionization probability as a function of pulse width; (d) Double ionization probability as a function of relative phases under different pulse widths, the${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ value is 2 for (c), (d)图 3 3种不同
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ 下电场振幅(红线, 任意单位)驱动电子轨线(黑线, 任意单位)的示意图: (a)${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ = 0.5; (b)${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ = 2; (c)${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ = 6Fig. 3 Schematic diagram of electric field amplitudes (red lines, a.u.) driving electron trajectories (black lines, a.u.) for three different
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ values; the${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ values are 0.5, 2, and 6 for (a), (b), and (c), respectively图 4 图中脉宽为10 fs, 光场强度为0.4 PW/cm2: (a)、(b 、(c)为3种不同
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ 下两个电子总能量的时间演化示意图; (d)、(e)、(f)为3种代表性的电子能量演化轨线,${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ 为2Fig. 4 The pulse width is 10 fs and the laser intensity is 0.4 PW/cm2: (a), (b), (c) Energy evolution diagram of two electrons in the ionization process at different
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ values; (d), (e), (f) Schematic diagram of three representative electron energy evolution processes; the${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ value is 2图 6 (a)、(b)、(c)、(d)分别为4种不同
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ 下电子返回动能分布示意图, 蓝色虚线表示双电离需要的能量(1.02 a.u.), 红色虚线表示电子的激发能(0.63 a.u.), 合场峰值强度为0.4 PW/cm2, 脉宽10 fsFig. 6 (a), (b), (c) and (d) are the distribution diagrams of the returned kinetic energy of electrons under four different
${{I}_{\rm{b}}}/{{I}_{{\rm{r}}}} $ values. The dotted blue line indicates the energy required for a double ionization (1.02 a.u.) and the dotted red line indicates the electron excitation energy (0.63 a.u.), the combined field peak intensity was 0.4 PW/cm2 and the pulse width was 10 fs -
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