Single-active-electron analysis of laser-polarization effects on atomic/molecular multiphoton excitation.
Single-active-electron analysis of laser-polarization effects on atomic/molecular multiphoton excitation.
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DOI：
10.1063/1.4994876
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发表时间：
2017-10
期刊：
影响因子：
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通讯作者：
M. Kanno;N. Inada;H. Kono
中科院分区：
文献类型：
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作者：
M. Kanno;N. Inada;H. Kono
我们从理论上探讨了光学椭圆率对强偏振激光场照射的原子和（接近）球形分子中单活性电子多光子激发的影响。这项工作是由 Hertel 等人的实验和理论研究推动的。 [物理。莱特牧师。 102, 023003 (2009) 和 Phys。 Rev. A 79, 053414 (2009)]，他报道了在低光强度下，氙和 C60 的近红外诱导离子产额作为椭圆率的函数（特别是圆偏振的产额减少）的显着变化，并通过假设系统的激发态能量和径向跃迁电偶极矩与方位角无关，导出了微扰截面公式来描述这种偏振效应量子数l.首先，通过重新表述单个活性电子的 N 光子吸收截面，我们证明他们的假设将光学允许的跃迁路径网络减少到我们所说的仅由 (N + 1) (N + 2)/2 态组成的“帕斯卡三角形”。接下来，不仅在低强度区域，而且在高强度区域，给出了简单的双光子激发模型的时间相关薛定谔方程的非微扰解析和数值解。结果表明，椭圆率相关的多光子激发概率的决定因素是跃迁矩幅度，并且系统的详细能量结构在高强度下也变得重要。实验观察到的氙和 C60 离子产率随强度增加而趋平的现象可以在没有饱和效应的情况下得到解释，而此前人们认为饱和效应是其原因。我们还论证了 Hertel 等人的横截面公式的适用范围。以及 C60 电离的“门口态”的身份。
We theoretically explore the effects of optical ellipticity on single-active-electron multiphoton excitation in atoms and (nearly) spherical molecules irradiated by intense polarized laser fields. This work was motivated by the experimental and theoretical studies of Hertel et al. [Phys. Rev. Lett. 102, 023003 (2009) and Phys. Rev. A 79, 053414 (2009)], who reported pronounced changes in the near-infrared-induced ion yields of xenon and C60 as a function of ellipticity (in particular, yield reduction for circular polarization) at low light intensities and derived a perturbative cross section formula to describe such polarization effects by assuming that the excited-state energies and radial transition electric dipole moments of the system are independent of the azimuthal quantum number l. First, by reformulating the N-photon absorption cross section of a single active electron, we prove that their assumptions reduce the network of optically allowed transition pathways into what we call the "Pascal triangle" consisting of (N + 1) (N + 2)/2 states only. Next, nonperturbative analytical and numerical solutions of the time-dependent Schrödinger equation for a simple model of two-photon excitation are presented not only in the low-intensity regime but also in the high-intensity regime. The results show that the determining factor of ellipticity-dependent multiphoton excitation probability is transition moment magnitudes and that the detailed energetic structure of the system also becomes important at high intensities. The experimentally observed flattening of the ion yields of xenon and C60 with increasing intensity can be explained without a saturation effect, which was previously deemed to be responsible for it. We also argue the applicability range of the cross section formula by Hertel et al. and the identity of the "doorway state" for ionization of C60.