The European Physical Journal D ( IF 1.5 ) Pub Date : 2021-07-09 , DOI: 10.1140/epjd/s10053-021-00214-4 Yuxin Kang 1 , Emilio Pisanty 2, 3 , Marcelo Ciappina 3, 4, 5 , Maciej Lewenstein 3, 6 , Carla Figueira de Morisson Faria 1 , Andrew S Maxwell 1, 3
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Abstract
We investigate twisted electrons with a well-defined orbital angular momentum, which have been ionised via a strong laser field. By formulating a new variant of the well-known strong field approximation, we are able to derive conservation laws for the angular momenta of twisted electrons in the cases of linear and circularly polarised fields. In the case of linear fields, we demonstrate that the orbital angular momentum of the twisted electron is determined by the magnetic quantum number of the initial bound state. The condition for the circular field can be related to the famous ATI peaks, and provides a new interpretation for this fundamental feature of photoelectron spectra. We find the length of the circular pulse to be a vital factor in this selection rule and, employing an effective frequency, we show that the photoelectron OAM emission spectra are sensitive to the parity of the number of laser cycles. This work provides the basic theoretical framework with which to understand the OAM of a photoelectron undergoing strong field ionisation.
Graphic Abstract
中文翻译：
强场电离中电子涡流的守恒定律
摘要
我们研究具有明确定义的轨道角动量的扭曲电子，这些电子已通过强激光场电离。通过制定著名的强场近似的新变体，我们能够推导出线性和圆极化场情况下扭曲电子的角动量的守恒定律。在线性场的情况下，我们证明了扭曲电子的轨道角动量由初始束缚态的磁量子数决定。圆形场的条件可能与著名的 ATI 峰有关，并为光电子能谱的这一基本特征提供了新的解释。我们发现圆形脉冲的长度是该选择规则中的一个重要因素，并且采用有效频率，我们表明，光电子 OAM 发射光谱对激光周期数的奇偶性敏感。这项工作为理解经历强场电离的光电子的 OAM 提供了基本的理论框架。
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