Extracting doubly-excited state lifetimes in helium directly in the time domain with attosecond noncollinear four-wave-mixing spectroscopy

arXiv - PHYS - Atomic Physics Pub Date : 2024-08-01 DOI:arxiv-2408.00209

Patrick RupprechtDepartment of Chemistry, University of California, Berkeley, California, USAChemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA, Nicolette G. PuskarDepartment of Chemistry, University of California, Berkeley, California, USAChemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA, Daniel M. NeumarkDepartment of Chemistry, University of California, Berkeley, California, USAChemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA, Stephen R. LeoneDepartment of Chemistry, University of California, Berkeley, California, USAChemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USADepartment of Physics, University of California, Berkeley, California, USA

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Abstract

The helium atom, with one nucleus and two electrons, is a prototypical system to study quantum many-body dynamics. Doubly-excited states, or quantum states in which both electrons are excited by one photon, are showcase scenarios of electronic-correlation mediated effects. In this paper, the natural lifetimes of the doubly-excited $^1$P$^o$ 2s$n$p Rydberg series and the $^1$S$^e$ 2p$^2$ dark state in helium in the 60 eV to 65 eV region are measured directly in the time domain with extreme-ultraviolet/near-infrared noncollinear attosecond four-wave-mixing (FWM) spectroscopy. The measured lifetimes are in agreement with lifetimes deduced from spectral linewidths and theoretical predictions, and the roles of specific decay mechanisms are considered. While complex spectral line shapes in the form of Fano resonances are common in absorption spectroscopy of autoionizing states, the background-free and thus homodyned character of noncollinear FWM results exclusively in Lorentzian spectral features in the absence of strong-field effects. The onset of strong-field effects that would affect the extraction of accurate natural lifetimes in helium by FWM is determined to be approximately 0.3 Rabi cycles. This study provides a systematic understanding of the FWM parameters necessary to enable accurate lifetime extractions, which can be utilized in more complex quantum systems such as molecules in the future.

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利用阿秒非共轭四波混合光谱直接在时域中提取氦的双激发态寿命

氦原子有一个原子核和两个电子，是研究量子多体动力学的典型系统。双激发态，即两个电子都被一个光子激发的量子态，是电子相关介导效应的展示场景。本文利用极紫外/近红外非共轭四次混频（FWM）光谱法，在时域内直接测量了氦中 60 eV 至 65 eV 区域的^1$P$^o$ 2s$n$p Rydberg 系列双激发态和^1$S$^e$ 2p$^2$ 暗态的自然寿命。测得的寿命与根据光谱线宽和理论预测推断的寿命一致，并考虑了特定衰变机制的作用。虽然法诺共振形式的复杂谱线形状在自电离状态的吸收光谱学中很常见，但非共振全武磁的无背景性和同调性在没有强场效应的情况下只产生洛伦兹谱线特征。强场效应的起始时间大约为 0.3 拉比周期。这项研究提供了对实现精确寿命提取所必需的 FWM 参数的系统性理解，将来可用于更复杂的量子系统（如分子）。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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arXiv - PHYS - Atomic Physics

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