Attosecond metrology of 2D charge distribution in molecules
V. Loriot, A. Boyer, S. Nandi, C. M. González-Collado, E. Plésiat, A. Marciniak, C. L. Garcia, Y. Hu, M. Lara-Astiaso, A. Palacios, P. Decleva, F. Martín, F. Lépine
光电离作为一种半散射过程并非瞬时发生。通常，光电离中的时间延迟约为几十阿秒（1 as = 10⁻¹⁸ s）。从单个原子过渡到纳米物体时，由于光电子在更大距离上发生散射，可以预期延迟会增加。本文表明，在平面体系中这一预期不再成立。利用阿秒干涉测量技术，我们发现二维碳基分子萘（naphthalene）中的时间延迟显著小于其三维类金刚石对应物金刚烷（adamantane）。测得的时间延迟携带了残余分子阳离子中所产生空穴的空间分布特征，使我们能够以埃级精度获得其尺寸。我们的发现为追踪和操控分子材料中的超快电荷输运提供了新的机遇。
英文摘要：
Photoionization as a half-scattering process is not instantaneous. Usually, time delays in photoionization are of the order of few tens of attoseconds (1 as = 10$^{-18}$ s). While going from a single atom to a nano-object, one can expect the delay to increase since the photoelectron scatters over a larger distance. Here, we show that this is no longer valid in the case of planar systems. Using attosecond interferometry, we find that the time delay in a 2D carbon-based molecule, naphthalene, is significantly smaller compared to its 3D diamond-like counterpart, adamantane. The measured time delay carries the signature of the spatial distribution of the hole created in the residual molecular cation, allowing us to obtain its dimensions with angstrom accuracy. Our findings offer novel opportunities for tracking and manipulating ultrafast charge transport in molecular materials.
Tracing ultrafast processes induced by interaction of light with matter is often very challenging. In molecular systems, the initially created electronic coherence becomes damped by the slow nuclear rearrangement on a femtosecond timescale which makes real-time observations of electron dynamics in molecules particularly difficult. In this work, we report an extension of the theory underlying the attosecond transient absorption spectroscopy (ATAS) for the case of molecules, including a full account for the coupled electron-nuclear dynamics in the initially created wave packet, and apply it to p…
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Zepto to Attosecond core-level photoemission time delays in homonuclear diatomic molecules and non-dipole effects in the framework of Multiple Scattering theory
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Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry an additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences and demonstrate how it offers a novel tool to monitor non-adiabatic dynamics as it occurs in the vicinity of conical intersections and …
Attosecond charge migration is a periodic evolution of the charge density of a molecule on a time scale defined by the energy intervals between the electronic states involved. Here, we report the observation of charge migration in neutral silane (SiH$_4$) in 690~as, its decoherence within 15~fs, and its revival after 40-50~fs using X-ray attosecond transient absorption spectroscopy. The migration of charge is observed as pairs of quantum beats with a characteristic spectral phase in the transient spectrum. The decay and revival of the degree of electronic coherence is found to be a result of b…
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Charge migration is the electronic response that immediately follows localized ionization or excitation in a molecule, before the nuclei have time to move. It typically unfolds on sub-femtosecond time scales and most often corresponds to dynamics far from equilibrium, involving multi-electron interactions in a complex chemical environment. While charge migration has been documented experimentally and theoretically in multiple organic and inorganic compounds, the general mechanism that regulates it remains unsettled. In this work we use tools from nonlinear dynamics to analyze charge migration …
Electron dynamics in water are of fundamental importance for a broad range of phenomena, but their real-time study faces numerous conceptual and methodological challenges. Here, we introduce attosecond size-resolved cluster spectroscopy and build up a molecular-level understanding of the attosecond electron dynamics in water. We measure the effect that the addition of single water molecules has on the photoionization time delays of water clusters. We find a continuous increase of the delay for clusters containing up to 4-5 molecules and little change towards larger clusters. We show that these…
Preparation and control of electronic wave packets in neutral molecules via attosecond x-ray processes
Technical University of Denmark（丹麦技术大学）；University of Hamburg（汉堡大学）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；The Hamburg Centre for Ultrafast Imaging（汉堡超快成像中心）；Friedrich Schiller University Jena（耶拿弗里德里希·席勒大学）；Q-Chem, Inc.（Q-Chem公司）；University of Southern California（南加州大学）
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In this work, we present a time-dependent (TD) selected configuration interaction method based on our recently-introduced adaptive configuration interaction (ACI). We show that ACI, in either its ground or excited state formalisms, is capable of building a compact basis for use in real-time propagation of wave functions for computing electron dynamics. TD-ACI uses an iteratively selected basis of determinants in real-time propagation capable of capturing strong correlation effects in both ground and excited states, all with an accuracy---and associated cost---tunable by the user. We apply TD-A…
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Time-resolved investigations of ultrafast electronic and molecular dynamics were not possible until recently. The typical time scale of these processes is in the picosecond to attosecond realm. The tremendous technological progress in recent years made it possible to generate ultrashort pulses, which can be used to trigger, to watch, and to control atomic and molecular motion. This tutorial focuses on experimental and theoretical advances which are used to study the dynamics of electrons and molecules in the presence of ultrashort pulses. In the first part, the rotational dynamics of molecules…
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A nonadiabatic scheme for the description of the coupled electron and nuclear motions in the ozone molecule was proposed recently. An initial coherent nonstationary state was prepared as a superposition of the ground state and the excited Hartley band. In this situation neither the electrons nor the nuclei are in a stationary state. The multiconfiguration time dependent Hartree method was used to solve the coupled nuclear quantum dynamics in the framework of the adiabatic separation of the time-dependent Schrödinger equation. The resulting wave packet shows an oscillation of the electron densi…
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High-order harmonic generation is a powerful and sensitive tool for probing atomic and molecular structures, combining in the same measurement an unprecedented attosecond temporal resolution with a high spatial resolution, of the order of the angstrom. Imaging of the outermost molecular orbital by high-order harmonic generation has been limited for a long time to very simple molecules, like nitrogen. Recently we demonstrated a technique that overcame several of the issues that have prevented the extension of molecular orbital tomography to more complex species, showing that molecular imaging c…
