近日，德国奥尔登堡大学的M. Wollenhaupt及其研究团队取得一项新进展。经过不懈努力，他们利用光电子涡流测量原子共振增强多光子电离的电离延迟。相关研究成果已于2024年12月16日在国际知名学术期刊《物理评论A》上发表。

该研究团队利用对光电子涡旋的相位敏感检测，研究了原子多光子电离（MPI）中的时间延迟。光电子涡旋是通过反旋圆极化（CRCP）超短双脉冲序列实现多光子电离而产生的。这些涡旋的特征在于，由每个脉冲产生的部分光电子波包发生拉姆齐型干涉，从而形成螺旋状的光电子动量分布（PMD）。螺旋臂的斜率以干涉测量的精度编码了部分波包之间的时间延迟。

研究人员利用飞秒CRCP白光超连续谱脉冲，研究了钾原子1+2共振增强多光子电离中的电离时间延迟。部分波包与一个参考波包发生成对干涉，产生了不同旋转对称性的涡旋，这些涡旋叠加形成了总的光电子动量分布。研究人员通过断层扫描重建了光电子动量分布，并使用三维傅里叶分析将其分解为各个涡旋。从涡旋的能量依赖谱相位中，研究人员检索到了约1飞秒量级的共振电离延迟，这远小于脉冲持续时间。这项研究结果展示了光电子涡旋在精确测定光电离时间延迟方面的强大能力，并为光电子时间测量技术开辟了新的前景，包括在阿秒时间尺度上测量电离延迟。

附：英文原文

Title: Measurement of ionization delays in atomic resonance-enhanced multiphoton ionization using photoelectron vortices

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

Issue&Volume: 2024/12/16

Abstract: We study time delays in atomic multiphoton ionization (MPI) using the phase-sensitive detection of photoelectron vortices. Photoelectron vortices are created by MPI with counterrotating circularly polarized (CRCP) ultrashort double-pulse sequences. The vortices are characterized by a spiral-shaped photoelectron momentum distribution (PMD) resulting from the Ramsey-type interference of the partial photoelectron wave packets created by each pulse. The slope of the spiral arms encodes the time delay between the partial wave packets with interferometric precision. We study the ionization time delay in the 1+2 resonance-enhanced multiphoton ionization of potassium atoms using femtosecond CRCP white-light supercontinuum pulses. Pairwise interference of the partial wave packets with a reference wave packet gives rise to vortices of different rotational symmetry, which are superimposed to form the total PMD. The PMD is reconstructed tomographically and decomposed into the vortices using three-dimensional Fourier analysis. From the energy-dependent spectral phases of the vortices, we retrieve a resonant ionization delay on the order of 1 fs, much shorter than the pulse duration. Our results demonstrate the power of photoelectron vortices for the accurate determination of photoionization time delays and open up new perspectives for photoelectron chronoscopy including the measurement of ionization delays on the attosecond timescale.

DOI: 10.1103/PhysRevA.110.063111

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.063111