Analysis of the multielectron dynamics in intense laser-induced ionization of CO by the time-dependent effective potentials for natural orbitals
Analysis of the multielectron dynamics in intense laser-induced ionization of CO by the time-dependent effective potentials for natural orbitals
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DOI：
10.1088/1361-6455/ab9f0e
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发表时间：
2020-07
期刊：
影响因子：
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通讯作者：
S. Ohmura;T. Kato;H. Ohmura;S. Koseki;H. Kono
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文献类型：
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作者：
S. Ohmura;T. Kato;H. Ohmura;S. Koseki;H. Kono
用多组态含时Hartree-Fock方法模拟了不同载流子包络相位的近红外λ=760 nm双周期脉冲辐照下CO分子的多电子动力学行为。模拟结果表明，当激光电场ɛ(T)从C指向O时，其电离速率高于从C指向O时的电离率，这与双色实验的结果一致。通过将所获得的多电子动力学转换为TD自然轨道{ϕj(T)}的形式，研究了CO隧道电离中的方向各向异性的机理。在MCTDHF框架下，我们推导了{ϕj(T)}的运动方程。从导出的方程出发，我们定义了支配ϕj(T)动力学的TD等效势Vjef(T)。Vjef(T)由包括与ɛ(T)相互作用的一体部分v1(T)和源于电子-电子相互作用的二体部分v2，j(T)组成。在5σHOMO的V5σEff(T)中，当σ(T)从C指向O时，v1(T)+v2，5σ(0)的场畸变势垒越过了与v2，5ɛ(T)有关的狭窄的驼峰，从而导致CO的各向异性电离。对于4σ，当σ(T)从C指向O时，在v4ɛEf(T)中形成了抑制电离的高势垒，这表明4σ和5σ电子之间存在着动力学关联。对于相反的相位，v4σff(T)变得无势垒，通过4σ增强高次谐波产生。我们还模拟了λ=380 nm脉冲的动力学过程，以研究v_5σff(T)如何反映脉冲的非绝热电子响应。我们发现，无论响应是否是绝热的，v1(0)+v2，5σ(T)中的驼峰高度与ϕ5σ(T)的诱导偶极矩几乎成正比。还给出了LiH的vHOMOef(T)，以说明驼峰结构的普遍存在。
We simulated the multielectron dynamics of a CO molecule irradiated by near-IR λ = 760 nm two-cycle pulses with different carrier envelope phases by using the multiconfiguration time-dependent (TD) Hartree–Fock (MCTDHF) method. The ionization rate estimated from the simulations is higher when the laser electric field ɛ(t) points from C to O than in the opposite case, in agreement with the results of two-color experiments. The mechanism of the directional anisotropy in tunnel ionization of CO was examined by converting the obtained multielectron dynamics to the representation in terms of TD natural orbitals {ϕj(t)}. Within the framework of MCTDHF, we derived the equations of motion for {ϕj(t)}. From the derived equations, we defined the TD effective potentials vjeff(t) that govern the dynamics of ϕj(t). vjeff(t) consists of the one-body part v1(t) including the interaction with ɛ(t) and the two-body part v2,j(t) originating from electron–electron interaction. In v5σeff(t) for the 5σ HOMO, a narrow hump associated with the increase in v2,5σ(t) is surmounted on the field-distorted barrier of v1(t) + v2,5σ(0) near the nucleus C when ɛ(t) points from C to O, which results in the anisotropic ionization of CO. For 4σ, a high barrier that suppresses ionization is formed in v4σeff(t) when ɛ(t) points from C to O, which suggests that dynamical correlation exists between 4σ and 5σ electrons on route to ionization. For the opposite phase, v4σeff(t) becomes barrierless, enhancing high-harmonic generation through 4σ. We also simulated the dynamics for a λ = 380 nm pulse to investigate how v5σeff(t) reflects the nonadiabatic electronic response to the pulse. We found that the height of the hump in v1(0) + v2,5σ(t) is nearly proportional to the induced dipole moment of ϕ5σ(t), irrespective of whether the response is adiabatic or not. The vHOMOeff(t) for LiH is also presented to demonstrate the ubiquity of hump structures.