整形自由电子涡旋
Shaped free electron vortices
AI总结：
本文首次实验演示反向啁啾 CRCP 飞秒脉冲对经原子多光子电离产生整形自由电子涡旋，并结合速度 map 成像、断层扫描与傅里叶分解揭示其光谱及动力学信息。
摘要：
自自由电子涡旋（FEVs）首次在理论上被提出［Ngoko Djiokap 等人，Phys. Rev. Lett. 115, 113004 (2015)］并在实验上得到演示［Pengel 等人，Phys. Rev. Lett. 118, 053003 (2017)］以来，它们已引起相当大的关注。最近，Strandquist 等人［Phys. Rev. A 106, 043110 (2022)］在理论上提出了一类新的、具有异常形状的 FEVs，称为“可逆电子螺旋”，用于由两个反向啁啾且反向旋转的圆偏振（CRCP）阿秒脉冲产生的原子单光子电离。基于这一概念，我们首次实验演示了利用反向啁啾的 CRCP 飞秒脉冲对通过原子多光子电离（MPI）产生的整形 FEVs。在偏振整形脉冲引发的 MPI 中，若干具有不同旋转对称性的整形 FEVs 相互叠加，形成实验中观测到的总光电子波包。我们采用速度 map 成像技术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 FEVs。实验结果得到解析模型的支持，并由数值模拟复现，从而揭示了共振中间态所起的作用。我们的方法能够从整形激光场中恢复光谱信息，以及提取铭刻在整形 FEVs 中的 MPI 动力学特征。
英文摘要：
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) have attracted considerable attention. Recently, a new class of unusually shaped FEVs, termed `reversible electron spirals', has been 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 the first 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.
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