Ultrafast charge migration by electron correlation

Cederbaum, Lorenz S.; Zobeley, Jürgen

doi:10.1016/s0009-2614(99)00508-4

Cited by 336 publications

(364 citation statements)

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“…The investigation of the inherent structural and dynamical anisotropies of polar molecules has however been prevented by the difficulty of orienting molecules. Interesting phenomena tied to polar molecules include the predicted recombination-site dependence of structural minima [14,15] and attosecond charge migration [16][17][18] triggered by strong-field ionization. Here, we demonstrate a protocol for molecular orientation which achieves macroscopic field-free orientation and exploit this progress to probe the anisotropy of photorecombination dipole moments at a molecular shape resonance.…”

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confidence: 99%

Two-Pulse Field-Free Orientation Reveals Anisotropy of Molecular Shape Resonance

2014

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We report the observation of macroscopic field-free orientation, i.e. more than 73 % of CO molecules pointing in the same direction. This is achieved through an all-optical scheme operating at high particle densities (> 10 17 cm −3 ) that combines a one-color (ω) and a two-color (ω + 2ω) non-resonant femtosecond laser pulses. We show that the achieved orientation solely relies on the hyperpolarizability interaction as opposed to an ionization-depletion mechanism thus opening a wide range of applications. The achieved strong orientation enables us to reveal the molecularframe anisotropies of the photorecombination amplitudes and phases caused by a shape resonance. The resonance appears as a local maximum in the even-harmonic emission around 28 eV. In contrast, the odd-harmonic emission is suppressed in this spectral region through the combined effects of an asymmetric photorecombination phase and a sub-cycle Stark effect, generic for polar molecules, that we experimentally identify.Techniques for fixing molecules in space are invaluable tools for a broad range of experiments in ultrafast science [1,2]. The availability of transiently aligned molecular samples has particularly advanced strong-field and attosecond spectroscopies, providing new insights into the electronic structure of molecules and its temporal evolution [3][4][5][6][7]. High-harmonic spectroscopy (HHS) provides a new access to the rich structures of photoionization continua, such as Cooper minima [8][9][10][11] and shape resonances [11][12][13]. The investigation of the inherent structural and dynamical anisotropies of polar molecules has however been prevented by the difficulty of orienting molecules. Interesting phenomena tied to polar molecules include the predicted recombination-site dependence of structural minima [14,15] and attosecond charge migration [16][17][18] triggered by strong-field ionization. Here, we demonstrate a protocol for molecular orientation which achieves macroscopic field-free orientation and exploit this progress to probe the anisotropy of photorecombination dipole moments at a molecular shape resonance.Successful approaches to laser-induced molecular orientation include the combination of an electrostatic field with a rapidly turned-off laser field [19], alignment in combination with quantum-state selection and a weak dc-field [20][21][22][23], adiabatic [24] and impulsive two-color orientation [25][26][27]. All of these techniques are subject to substantial limitations: The presence of electric fields may alter the electronic structure of the molecule, its photo-induced dynamics or the subsequent probing process. The low particle densities available after quantumstate selection make the application of such techniques to high-harmonic and attosecond spectroscopies challenging to impossible. The two-color scheme [22,25], recently applied to HHS [26,27], relies on an ionization-depletion mechanism [28] and thus ties the achievable degree of orientation to the ionization fraction of the sample. This fact does not only limi...

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confidence: 99%

Two-Pulse Field-Free Orientation Reveals Anisotropy of Molecular Shape Resonance

2014

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“…A principal tool of attophysics, attosecond streaking spectroscopy [3] can resolve the ultrafast dynamics in atoms and condensed matter involving the emission of photo-or secondary electrons. This excludes the ultrafast electron transitions of the bound-bound type, for example the migration of an inner-valence electron hole driven by electron correlation [4][5][6] (see Ref. [7] for a recent theoretical work on photon emission spectroscopy of hole migration).…”

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Single-Photon Laser-Enabled Auger Spectroscopy for Measuring Attosecond Electron-Hole Dynamics

Cooper

Averbukh

2013

Phys. Rev. Lett.

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We propose and simulate a new type of attosecond time-resolved spectroscopy of electron hole dynamics, applicable particularly to ultrafast hole migration. Attosecond ionization in the innervalence region is followed by a VUV probe inducing single-photon laser-enabled Auger decay, a onephoton two-electron transition filling the inner-valence vacancy. The double ionization probability as a function of the attosecond pump-VUV probe delay captures efficiently the ultrafast innervalence hole dynamics. Detailed ab initio calculations are presented for inner-valence hole migration in glycine.

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“…due to nuclear motion, is well-known. More recently, charge migration has been found to occur in which the electron density moves, typically after ionisation, over a static nuclear framework [1,2]. It is due to the fact that a number of eigenstates of the ion contain contributions from the molecular orbital from which the electron is removed.…”

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confidence: 99%

Using quantum dynamics simulations to follow the competition between charge migration and charge transfer in polyatomic molecules

et al. 2017

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Recent work, particularly by Cederbaum and co-workers, has identified the phenomenon of charge migration, whereby charge flow occurs over a static molecular framework after the creation of an electronic wavepacket. In a real molecule, this charge migration competes with charge transfer, whereby the nuclear motion also results in the re-distribution of charge. To study this competition, quantum dynamics simulations need to be performed. To break the exponential scaling of standard grid-based algorithms, approximate methods need to be developed that are efficient yet able to follow the coupled electron-nuclear motion of these systems. Using a simple model Hamiltonian based on the ionisation of the allene molecule, the performance of different methods based on Gaussian Wavepackets is demonstrated.

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Ultrafast charge migration by electron correlation

Cited by 336 publications

References 14 publications

Two-Pulse Field-Free Orientation Reveals Anisotropy of Molecular Shape Resonance

Two-Pulse Field-Free Orientation Reveals Anisotropy of Molecular Shape Resonance

Single-Photon Laser-Enabled Auger Spectroscopy for Measuring Attosecond Electron-Hole Dynamics

Using quantum dynamics simulations to follow the competition between charge migration and charge transfer in polyatomic molecules

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