The European Physical Journal D ( IF 1.5 ) Pub Date : 2021-07-16 , DOI: 10.1140/epjd/s10053-021-00218-0 Severin Meister 1 , Hannes Lindenblatt 1 , Florian Trost 1 , Thomas Pfeifer 1 , Robert Moshammer 1 , Aaron Bondy 2, 3 , Klaus Bartschat 2 , Kirsten Schnorr 4 , Sven Augustin 4 , Xinhua Xie 4 , Markus Braune 5 , Bastian Manschwetus 5 , Nora Schirmel 5 , Harald Redlin 5 , Nicolas Douguet 6
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Abstract
Ionization of laser-dressed atomic helium is investigated with focus on photoelectron angular distributions stemming from two-color multi-photon excited states. The experiment combines extreme ultraviolet (XUV) with infrared (IR) radiation, while the relative polarization and the temporal delay between the pulses can be varied. By means of an XUV photon energy scan over several electronvolts, we get access to excited states in the dressed atom exhibiting various binding energies, angular momenta, and magnetic quantum numbers. Furthermore, varying the relative polarization is employed as a handle to switch on and off the population of certain states that are only accessible by two-photon excitation. In this way, photoemission can be suppressed for specific XUV photon energies. Additionally, we investigate the dependence of the photoelectron angular distributions on the IR laser intensity. At our higher IR intensities, we start leaving the simple multi-photon ionization regime. The interpretation of the experimental results is supported by numerically solving the time-dependent Schrödinger equation in a single-active-electron approximation.
Graphic abstract
中文翻译：
激光修整氦的少光子电离中的线性二色性
摘要
研究了激光修饰的原子氦的电离，重点是源于双色多光子激发态的光电子角分布。该实验结合了极紫外 (XUV) 和红外 (IR) 辐射，同时可以改变脉冲之间的相对极化和时间延迟。通过在几个电子伏特上进行 XUV 光子能量扫描，我们可以访问表现出各种结合能、角动量和磁量子数的装饰原子中的激发态。此外，改变相对极化被用作打开和关闭某些只能通过双光子激发才能访问的状态的控制。通过这种方式，可以抑制特定 XUV 光子能量的光发射。此外，我们研究了光电子角分布对红外激光强度的依赖性。在我们更高的红外强度下，我们开始离开简单的多光子电离机制。通过在单活性电子近似中数值求解与时间相关的薛定谔方程来支持对实验结果的解释。
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