近日，德国奥尔登堡大学的M. Wollenhaupt及其研究团队，报道了他们对成形自由电子涡旋的研究。相关研究成果已于2024年11月20日在国际知名学术期刊《物理评论A》上发表。

自自由电子涡旋（FEV）首次被理论提出[Ngoko Djiokap等人，《物理评论快报》115, 113004 (2015)]和实验验证[Pengel等人，《物理评论快报》118, 053003 (2017)]以来，在光驱动过程中制备的FEV已引起了广泛关注。

最近，理论上提出了一种新型的非寻常成形FEV，称为“可逆电子螺旋”[Strandquist等人，《物理评论A》106, 043110 (2022)]，它是由两个相反手性且反向旋转的圆极化（CRCP）阿秒脉冲引起的，原子单光子电离所产生的。

基于这一概念，该研究团队实验演示了使用相反手性的CRCP飞秒脉冲，对通过原子多光子电离（MPI）产生的成形FEV。在极化整形脉冲引起的MPI中，几个不同旋转对称性的形状可控FEV相互叠加，形成了实验中观察到的总光电子波包。

研究人员采用速度映射成像技术来测量光电子动量分布（PMD），并通过光电子断层扫描重建三维PMD。利用傅里叶分析将测得的PMD分解为，具有不同旋转对称性的贡献FEV。

实验结果得到了分析模型的支持，并通过数值模拟得以复现，从而深入了解了共振中间态的作用。这项研究方法使他们能够从整形激光场中检索光谱信息，并揭示记录在成形FEV中的MPI动力学特征。

附：英文原文

Title: Shaped free-electron vortices

Author: D. Khnke, T. Bayer, M. Wollenhaupt

Issue&Volume: 2024/11/20

Abstract: Since their first theoretical proposal [Ngoko Djiokap et al., Phys. Rev. Lett. 115, 113004 (2015)] and experimental demonstration [Pengel et al., Phys. Rev. Lett. 118, 053003 (2017)], free electron vortices (FEVs) prepared in light-driven processes have attracted considerable attention. Recently, a new class of unusually shaped FEVs, termed “reversible electron spirals,” was proposed theoretically [Strandquist et al., Phys. Rev. A 106, 043110 (2022)] for atomic single-photon ionization by two oppositely chirped and counterrotating circularly polarized (CRCP) attosecond pulses. Building on this concept, we present an experimental demonstration of shaped FEVs created by atomic multiphoton ionization (MPI) using oppositely chirped CRCP femtosecond pulse pairs. In MPI by polarization-shaped pulses, several shaped FEVs of different rotational symmetry are superimposed resulting in the total photoelectron wave packet observed in the experiment. We employ velocity map imaging techniques to measure the photoelectron momentum distribution (PMD) and reconstruct the three-dimensional PMD by photoelectron tomography. Fourier analysis is used to decompose the measured PMD into the contributing FEVs with different rotational symmetries. The experimental results are supported by an analytical model and reproduced by numerical simulations, which provide insight into the role of resonant intermediate states. Our approach allows us to retrieve spectral information from the shaped laser field and the signatures of the MPI dynamics inscribed within the shaped FEVs.

DOI: 10.1103/PhysRevA.110.053109

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.053109