Probing Attosecond Electron Coherence in Molecular Charge Migration by Ultrafast X-Ray Photoelectron Imaging

Yuan, Kai-Jun; Bandrauk, André D.

doi:10.3390/app9091941

Cited by 10 publications

(9 citation statements)

References 63 publications

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“…For the optical responses in Figure 3B of the molecule H + 2 perpendicular to the laser (x, y) polarization plane, R ⊥ E, Figure 1B, by a single 70-nm circularly polarized pulse, resonant excitation between the ground σ g state and the excited π + u state with magnetic quantum number Δm 1 leads to ring electron currents in molecules [64,67]. As shown in Supplementary Appendix A2, using the electronic angular continuity equation [16,17],…”

Section: Resonant Excitation In the Case Of Around-axis R ⊥ Ementioning

confidence: 99%

Electronic Currents and Magnetic Fields in H2+ Induced by Coherent Resonant Bichromatic Circularly Polarized Laser Pulses: Effects of Orientation, Phase, and Helicity

2021

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We theoretically study pulse phase and helicity effects on ultrafast magnetic field generation in intense bichromatic circularly polarized laser fields. Simulations are performed on the aligned molecular ion H2+ from numerical solutions of corresponding time-dependent Schrödinger equations. We demonstrate how electron coherent resonant excitation influences the phase and helicity of the optically induced magnetic field generation. The dependence of the generated magnetic field on the pulse phase arises from the interference effect between multiple excitation and ionization pathways, and is shown to be sensitive to molecular alignment and laser polarization. Molecular resonant excitation induces coherent ring electron currents, giving enhancement or suppression of the phase dependence. Pulse helicity effects control laser-induced electron dynamics in bichromatic circular polarization excitation. These phenomena are demonstrated by a molecular attosecond photoionization model and coherent electron current theory. The results offer a guiding principle for generating ultrafast magnetic fields and for studying coherent electron dynamics in complex molecular systems.

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Section: Resonant Excitation In the Case Of Around-axis R ⊥ Ementioning

confidence: 99%

Electronic Currents and Magnetic Fields in H2+ Induced by Coherent Resonant Bichromatic Circularly Polarized Laser Pulses: Effects of Orientation, Phase, and Helicity

2021

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“…Basis sets were applied to separate part of the variables in prolate spheroidal coordinates for the H 2 molecule (Awasthi et al, 2005;Guan et al, 2011). Two-and three dimensional grids in cylindrical coordinates without basis expansions were used in solving the TDSE for single-electron problems (Kulander, 1987;Yuan and Bandrauk, 2019).…”

Section: Solution Of the Tdse On The Space-time Gridmentioning

confidence: 99%

Atomic, molecular and optical physics applications of longitudinally coherent and narrow bandwidth Free-Electron Lasers

Callegari,

Grum-Grzhimailo,

Ishikawa

et al. 2020

Preprint

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Short wavelength Free-Electron Lasers (FELs) are the newest light sources available to scientists to probe a wide range of phenomena, with chemical, physical and biological applications, using soft and hard X-rays. These sources include the currently most powerful light sources in the world (hard X-ray sources) and are characterised by extremely high powers and high transverse coherence, but the first FELs had reduced longitudinal coherence. Now it is possible to achieve good longitudinal coherence (narrow bandwidth in the frequency domain) and here we discuss and illustrate a range of experiments utilising this property, and their underlying physics. The primary applications are those which require high resolution (for example resonant experiments), or temporal coherence (for example coherent control experiments). The currently available light sources extend the vast range of laboratory laser techniques to short wavelengths.

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“…Measuring subfemtosecond electron dynamics in molecules and materials has been the focus of much recent interest. These dynamics, which result from a coherent superposition of states, occur at time scales faster than nuclear motion. − These dynamics form the initial stages of photochemical and light-harvesting processes, which are still poorly understood. In solids, electron dynamics resulting from intense laser pulses result in band dynamics such as band distortion and valence band/conduction band redistribution − and result in strong-field effects like negative-differential conductivity .…”

Section: Introductionmentioning

confidence: 99%

First-Principles Simulations of X-ray Transient Absorption for Probing Attosecond Electron Dynamics

Chen

Lopata

2020

J. Chem. Theory Comput.

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X-ray transient absorption spectroscopy (XTAS) is a promising technique for measuring electron dynamics in molecules and solids with attosecond time resolutions. In XTAS, the elemental specificity and spatial locality of core-to-valence X-ray absorption is exploited to relate modulations in the time-resolved absorption spectra to local electron density variations around particular atoms. However, interpreting these absorption modulations and frequency shifts as a function of the time delay in terms of dynamics can be challenging. In this paper, we present a first-principles study of attosecond XTAS in a selection of simple molecules based on real-time time-dependent density functional theory (RT-TDDFT) with constrained DFT to emulate the state of the system following the interaction with a ultraviolet pump laser. In general, there is a decrease in the optical density and a blue shift in the frequency with increasing electron density around the absorbing atom. In carbon monoxide (CO), modulations in the O K-edge occur at the frequency of the valence electron dynamics, while for dioxygen (O 2 ) they occur at twice the frequency, due to the indistinguishability of the oxygen atoms. In 4-aminophenol (H 2 NC 6 H 4 OH), likewise, there is a decrease in the optical density and a blue shift in the frequency for the oxygen and nitrogen K-edges with increasing charge density on the O and N, respectively. Similar effects are observed in the nitrogen K-edge for a long-range charge-transfer excitation in a benzene (C 6 H 6 )–tetracyanoethylene (C 6 N 4 ; TCNE) dimer but with weaker modulations due to the delocalization of the charge across the entire TCNE molecule. Additionally, in all cases, there are pre-edge features corresponding to core transitions to depopulated orbitals. These potentially offer a background-free signal that only appears in pumped molecules.

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Probing Attosecond Electron Coherence in Molecular Charge Migration by Ultrafast X-Ray Photoelectron Imaging

Cited by 10 publications

References 63 publications

Electronic Currents and Magnetic Fields in H2+ Induced by Coherent Resonant Bichromatic Circularly Polarized Laser Pulses: Effects of Orientation, Phase, and Helicity

Electronic Currents and Magnetic Fields in H2+ Induced by Coherent Resonant Bichromatic Circularly Polarized Laser Pulses: Effects of Orientation, Phase, and Helicity

Atomic, molecular and optical physics applications of longitudinally coherent and narrow bandwidth Free-Electron Lasers

First-Principles Simulations of X-ray Transient Absorption for Probing Attosecond Electron Dynamics

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