Time delays from one-photon transitions in the continuum
Time delays from one-photon transitions in the continuum
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DOI：
10.1364/optica.378639
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发表时间：
2020-02-20
期刊：
影响因子：
10.4
通讯作者：
Keller, Ursula
中科院分区：
文献类型：
--
作者：
Fuchs, Jaco;Douguet, Nicolas;Keller, Ursula
阿秒光电离时间延迟揭示了有关电离时传出电子波包探测的势能景观的信息。在这项研究中，我们通过实验量化了时间延迟对释放光电子角动量的依赖性。为此，我们使用氦气中的双色阿秒泵浦探针光电离实验解析了能量和角度的电子量子路径干涉光谱。角度相关干涉图样的拟合过程使我们能够解开已知对最终光电子信号有贡献的所有四个量子路径的相对相位。特别是，我们解决了连续态之间单光子跃迁延迟对角动量的依赖性，这是对阿秒泵浦探针测量中观察到的总光电离延迟的重要且普遍的贡献。对于这种连续谱-连续谱跃迁，我们测量了输出 s 和 d 电子之间的延迟高达 12 阿秒，相当于氦气的电离阈值。单活性电子和第一原理从头开始模拟都证实了氦和氢的这一观察结果，证明了观察到的延迟的普遍性。由光学协会根据知识共享署名 4.0 许可条款发布。
Attosecond photoionization time delays reveal information about the potential energy landscape that an outgoing electron wavepacket probes upon ionization. In this study, we experimentally quantify the dependence of the time delay on the angular momentum of the liberated photoelectrons. For this purpose, we resolved electron quantum-path interference spectra in energy and angle using a two-color attosecond pump-probe photoionization experiment in helium. A fitting procedure of the angle-dependent interference pattern allows us to disentangle the relative phase of all four quantum pathways that are known to contribute to the final photoelectron signal. In particular, we resolve the dependence on angular momentum of the delay of one-photon transitions between continuum states, which is an essential and universal contribution to the total photoionization delay observed in attosecond pump-probe measurements. For such continuum-continuum transitions, we measure a delay between outgoing s and d electrons as large as 12 attoseconds, dose to the ionization threshold in helium. Both single-active-electron and first-principles ab initio simulations confirm this observation for helium and hydrogen, demonstrating the universality of the observed delays. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.