Attosecond Photoemission Dynamics: Novel AB Initio Methods for Atomic and Molecular Ex-situ Spectrscopies

阿秒光电子发射动力学：原子和分子异位光谱的新型 AB 从头算方法

• 批准号: 1912507
• 负责人: Luca Argenti
• 金额: $ 32.7万
• 依托单位: The University of Central Florida Board of Trustees
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1912507&HistoricalAwards=false
• 关键词: Attosecond; Photoemission; Dynamics; Novel; AB

At a fundamental level, atoms consists of negatively-charge particles, the electrons, flying around a massive positively-charged nucleus. Using ultrashort laser pulses, snapshots of electrons can be taken with attosecond time resolution (one attosecond is a billionth of a billionth of a second), which is the natural timescale of electronic motion. To control how atoms evolve in time, however, it is also essential to be able to predict their fast dynamics. This is a difficult task because electrons try to avoid each other in their motion around the nucleus. Furthermore, electrons occasionally do collide, causing the choreography of the dance to change. During the last three years, this research group has developed numerical tools that can predict how this complex dynamics unfolds under the influence of external light pulses. The present project will add to the theoretical toolbox the pieces necessary to describe three important aspects of electron dynamics; the interaction of their spin with their orbital motion, their interaction with circularly polarized light, and, in the case of molecular electrons, their interaction with two or more nuclear centers. These new tools will contribute to consolidate the U.S. presence in the ultrafast atomic and molecular international community, and to equip the students involved in this research with unique computational skills.Attosecond pulses have given access to the time-resolved study of electronic excitations in atoms and molecules above their ionization threshold. Such studies rely on ever more sophisticated theoretical models. Currently, it is possible to describe, within the electrostatic approximation, the ionization of systems as complex as neon and argon. Yet, the accurate treatment of atoms beyond the first period requires incorporation of their spin-orbit interaction. Thanks to constant experimental advances, the polarization of attosecond light pulses can now be changed at will, and it is possible to detect angularly resolved photoelectron spectra from oriented molecular targets. This project will include spin-orbit effects and the interaction with arbitrarily polarized pulses in the time-resolved description of atomic ionization, and it will extend existing molecular scattering codes to finite-pulse multi-photon ionization regimes. The inclusion of relativistic interactions will be essential to quantify the ionization delay due to the interplay between spin-orbit interaction and electron correlations. The study of ionization with arbitrarily polarized ultrashort pulses will open the way to non-axially symmetric photoemission. The new molecular-codes will be a more rigorous basis for attosecond interferometric spectroscopies. This project aims at solving persistent discrepancies in atomic attosecond experiments that are due to the non-negligible spin-orbit splitting in the valence and inner-valence shells of atoms as heavy as argon and krypton. It will explore new pump-prope schemes with circularly-polarized pulses, which hold the keys to the direct measurement of resonant retardation in photoemission and to the dichroism in the ionization of chiral systems. This project will also foster STEM excellence in Florida by promoting the participation of students from local high schools to the USA Physics Olympiads through off-campus training sessions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

从根本上讲，原子由带负电的粒子（即电子）组成，围绕着一个巨大的带正电的原子核飞行。使用超短激光脉冲，可以以阿秒时间分辨率（一阿秒是十亿分之一秒）拍摄电子快照，这是电子运动的自然时间尺度。然而，为了控制原子如何随时间演化，还必须能够预测它们的快速动态。这是一项艰巨的任务，因为电子在围绕原子核运动时试图相互避开。此外，电子偶尔也会发生碰撞，导致舞蹈的编排发生变化。在过去三年中，该研究小组开发了数值工具，可以预测这种复杂的动力学在外部光脉冲的影响下如何展开。本项目将向理论工具箱添加描述电子动力学三个重要方面所需的部分；它们的自旋与轨道运动的相互作用，它们与圆偏振光的相互作用，以及在分子电子的情况下，它们与两个或多个核中心的相互作用。这些新工具将有助于巩固美国在超快原子和分子国际界的地位，并使参与这项研究的学生具备独特的计算技能。阿秒脉冲使人们能够对原子和分子中的电子激发进行时间分辨研究。分子高于其电离阈值。此类研究依赖于更加复杂的理论模型。目前，可以在静电近似内描述氖气和氩气等复杂系统的电离。然而，对第一周期之后的原子的精确处理需要结合它们的自旋轨道相互作用。由于不断的实验进展，阿秒光脉冲的偏振现在可以随意改变，并且可以检测来自定向分子目标的角分辨光电子光谱。该项目将在原子电离的时间分辨描述中包括自旋轨道效应以及与任意偏振脉冲的相互作用，并将现有的分子散射代码扩展到有限脉冲多光子电离体系。由于自旋轨道相互作用和电子相关性之间的相互作用，相对论相互作用的包含对于量化电离延迟至关重要。任意偏振超短脉冲电离的研究将为非轴对称光电发射开辟道路。新的分子代码将成为阿秒干涉光谱学更严格的基础。该项目旨在解决原子阿秒实验中持续存在的差异，这些差异是由于氩和氪等重原子的价层和内价层中不可忽略的自旋轨道分裂造成的。它将探索新的圆偏振脉冲泵浦方案，该方案掌握着直接测量光电子发射共振延迟和手性系统电离二色性的关键。该项目还将通过校外培训课程促进当地高中学生参加美国物理奥林匹克竞赛，从而促进佛罗里达州 STEM 的卓越发展。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力评估进行评估，被认为值得支持。优点和更广泛的影响审查标准。

项目成果

Attosecond photoelectron spectroscopy of helium doubly excited states

氦双激发态阿秒光电子能谱

• DOI: 10.1103/physrevresearch.5.033047
• 发表时间: 2023
• 期刊: Physical Review Research
• 影响因子: 4.2
• 作者: Argenti, Luca;Lindroth, Eva
• 通讯作者: Lindroth, Eva

Autoionizing Polaritons in Attosecond Atomic Ionization

阿秒原子电离中的自电离极化子

• DOI: 10.1103/physrevlett.127.023202
• 发表时间: 2021
• 期刊: Physical Review Letters
• 影响因子: 8.6
• 作者: Harkema, N.;Cariker, C.;Lindroth, E.;Argenti, L.;Sandhu, A.
• 通讯作者: Sandhu, A.

Time delays from one-photon transitions in the continuum

• DOI: 10.1364/optica.378639
• 发表时间: 2020-02-20
• 期刊: OPTICA
• 影响因子: 10.4
• 作者: Fuchs, Jaco;Douguet, Nicolas;Keller, Ursula
• 通讯作者: Keller, Ursula

Multipolariton control in attosecond transient absorption of autoionizing states

自电离态阿秒瞬态吸收的多极化控制

• DOI: 10.1103/physreva.105.063107
• 发表时间: 2022
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Yanez-Pagans, S.;Cariker, C.;Shaikh, M.;Argenti, L.;Sandhu, A.
• 通讯作者: Sandhu, A.

Photoionization cross sections and photoelectron angular distributions of molecules with XCHEM-2.0

• DOI: 10.1016/j.cpc.2023.109033
• 发表时间: 2023-12
• 期刊: Comput. Phys. Commun.
• 作者: V. J. Borràs;P. Fernández-Milán;L. Argenti;J. González-Vázquez;Fernando Martín