Dynamics of valence-shell electrons and nuclei probed by strong-field holography and rescattering

Walt, Samuel G.; Ram, N. Bhargava; Atala, Marcos; Shvetsov-Shilovski, N. I.; Conta, Aaron von; Baykusheva, Denitsa; Lein, Manfred; Wörner, Hans Jakob

doi:10.1038/ncomms15651

Cited by 107 publications

(86 citation statements)

References 43 publications

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“…We, however, note that electronic superposition states have also been created in neutral molecules using impulsive stimulated Raman scattering 42 . The electronic dynamics of this superposition state have been followed by high-harmonic spectroscopy 42–44 and photoelectron holography 45 . Since both of these techniques offer sub-cycle temporal resolution, 46–50 they will also be suitable for following charge migration in neutral molecules 30,31,35,39,51 .…”

Section: Basic Conceptsmentioning

confidence: 99%

Charge migration and charge transfer in molecular systems

Wörner

Arrell

Banerji

et al. 2017

Structural Dynamics

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The transfer of charge at the molecular level plays a fundamental role in many areas of chemistry, physics, biology and materials science. Today, more than 60 years after the seminal work of R. A. Marcus, charge transfer is still a very active field of research. An important recent impetus comes from the ability to resolve ever faster temporal events, down to the attosecond time scale. Such a high temporal resolution now offers the possibility to unravel the most elementary quantum dynamics of both electrons and nuclei that participate in the complex process of charge transfer. This review covers recent research that addresses the following questions. Can we reconstruct the migration of charge across a molecule on the atomic length and electronic time scales? Can we use strong laser fields to control charge migration? Can we temporally resolve and understand intramolecular charge transfer in dissociative ionization of small molecules, in transition-metal complexes and in conjugated polymers? Can we tailor molecular systems towards specific charge-transfer processes? What are the time scales of the elementary steps of charge transfer in liquids and nanoparticles? Important new insights into each of these topics, obtained from state-of-the-art ultrafast spectroscopy and/or theoretical methods, are summarized in this review.

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Section: Basic Conceptsmentioning

confidence: 99%

Charge migration and charge transfer in molecular systems

Wörner

Arrell

Banerji

et al. 2017

Structural Dynamics

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184

163

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“…All data presented in this article have been recorded using a two-color pump-probe scheme utilizing low-orderharmonic generation (LOHG) in a semi-innite gas cell, and a velocity-map-imaging spectrometer (VMIS) 39,40 . The setup is schematically depicted in Figure 2.…”

Section: Methodsmentioning

confidence: 99%

Time-resolved photoelectron imaging with a femtosecond vacuum-ultraviolet light source: Dynamics in the A∼/B∼- and F∼-bands of SO2

Svoboda

Ram

Rajeev

et al. 2017

The Journal of Chemical Physics

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Time-resolved photoelectron imaging is demonstrated using the third harmonic of a 400-nm femtosecond laser pulse as the ionization source. The resulting 133-nm pulses are combined with 266-nm pulses to study the excited-state dynamics in theÃ/B-andF-band regions of SO 2 . The photoelectron signal from the molecules excited to theÃ/B-band does not decay for at least several picoseconds, reecting the population of bound states. The temporal variation of the photoelectron angular distribution (PAD) reects the creation of a rotational wave packet in the excited state. In contrast, the photoelectron signal from molecules excited to theF-band decays with a time constant of 80 fs. This time constant is attributed to the motion of the excited-state wave packet out of the ionization window. The observed time-dependent PADs are consistent with theF band corresponding to a Rydberg state of dominant s character. These results establish loworder harmonic generation as a promising tool for time-resolved photoelectron imaging of the excited-state dynamics of molecules, simultaneously giving access to low-lying electronic states, as well as Rydberg states, and avoiding the ionization of unexcited molecules.

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“…Our quantitative interpretation of the PMDs from atoms by means of a powerful semiclassical model forms the foundation for the future analysis of more complex system with e.g. non-trivially polarized fields [53][54][55] or more complex targets such as molecules [22,23,[56][57][58]. We expect that the changed focal-point structure influences decisively the resulting PMDs.…”

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confidence: 98%

“…For linearly polarized laser pulses, the PMDs are dominated by photoelectron holography [15,17]. Since these holograms [18] may be qualitatively explained by the interference of a non-scattered "reference" wave packet and a scattered "signal" wave packet [19,20], they have been applied for ultrafast imaging [21][22][23].While PMDs obtained by numerical solution of the time-dependent Schrödinger equation (TDSE) in full dimensionality (3D) agree well with experimental data [15,17], PMDs obtained in reduced dimensionality (2D) are unable to reproduce quantitatively the fringe positions and emission strength of the experiment [21]. Indeed, by direct comparison we find that the positions of the holographic fringes in the numerical solution of the TDSE in 3D differ from those in 2D.…”

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confidence: 99%

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Gouy’s Phase Anomaly in Electron Waves Produced by Strong-Field Ionization

2020

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Ionization of atoms by linearly polarized strong laser fields produces cylindrically symmetric photoelectron momentum distributions that exhibit modulations due to the interference of outgoing electron trajectories. For a faithful modeling, it is essential to include previously overlooked phase jumps occurring when trajectories pass through focal points. Such phase jumps are known as Gouy's phase anomaly in optics or as Maslov phases in semiclassical theory. Most importantly, because of Coulomb focusing in three dimensions, one out of two trajectories in photoelectron holography goes through a focal point as it crosses the symmetry axis in momentum space. In addition, there exist observable Maslov phases already in two dimensions. Clustering algorithms enable us to implement a semiclassical model with the correct preexponential factor that affects both the weight and the phase of each trajectory. We also derive a simple rule to relate two-dimensional and three-dimensional models. It explains the shifted interference fringes and weaker high-energy yield in three dimensions. The results are in excellent agreement with solutions of the time-dependent Schrödinger equation.The π phase shift of an electromagnetic wave as it passes through a focus is an astonishing effect. Even though it was already observed by Gouy [1] more than 100 years ago, recent advances in laser technology have shone new light on Gouy's phase [2][3][4][5]. Analogous phenomena have also been found in other types of waves such as acoustic waves [6], standing microwaves [7] and phonon-polariton wave packets in Raman scattering [8].In the past years, various experiments have been proposed and conducted for measuring the Gouy phase in matter waves [9][10][11]. In the present work, we demonstrate that Gouy's phase anomaly appears in electron wave packets produced by strong-field ionization leading to a significant imprint on interference structures in photoelectron momentum distributions (PMDs).Strong-field ionization may be viewed as a two-step process consisting of: (i) release of an electron from the target; (ii) acceleration of the electron by the electromagnetic field in presence of the potential of the parent ion [12,13]. Depending on the system geometry, different parts of the emitted wave packets are mapped to the same final momentum, creating interference structures [14][15][16]. As the positions of the interference fringes are determined by the phase difference between the wave packets, the emerging PMDs may be viewed as "phasometer". For linearly polarized laser pulses, the PMDs are dominated by photoelectron holography [15,17]. Since these holograms [18] may be qualitatively explained by the interference of a non-scattered "reference" wave packet and a scattered "signal" wave packet [19,20], they have been applied for ultrafast imaging [21][22][23].While PMDs obtained by numerical solution of the time-dependent Schrödinger equation (TDSE) in full dimensionality (3D) agree well with experimental data [15,17], PMDs obtained in reduced dimensi...

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Dynamics of valence-shell electrons and nuclei probed by strong-field holography and rescattering

Cited by 107 publications

References 43 publications

Charge migration and charge transfer in molecular systems

Charge migration and charge transfer in molecular systems

Time-resolved photoelectron imaging with a femtosecond vacuum-ultraviolet light source: Dynamics in the A∼/B∼- and F∼-bands of SO2

Gouy’s Phase Anomaly in Electron Waves Produced by Strong-Field Ionization

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