Catching Conical Intersections in the Act: Monitoring Transient Electronic Coherences by Attosecond Stimulated X-Ray Raman Signals

Kowalewski, Markus; Bennett, Kochise; Dorfman, Konstantin E.; Mukamel, Shaul

doi:10.1103/physrevlett.115.193003

Cited by 155 publications

(209 citation statements)

References 45 publications

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“…Recently, the development of nonlinear optics has allowed to conceive new vibrational spectroscopies based on pulsed lasers . In particular, broadband stimulated Raman spectroscopy (SRS) interrogates the sample through the joint action of a pair of overlapped Raman pulse (RP) and probe pulse (PP) at different wavelengths.…”

Section: Introductionmentioning

confidence: 99%

Resonant broadband stimulated Raman scattering in myoglobin

Ferrante

Batignani

Fumero

et al. 2018

J Raman Spectroscopy

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Spontaneous Raman is a well‐established tool to probe molecular vibrations. Under resonant conditions, it is a largely used method for characterizing the structure of heme‐proteins. In recent years, advances in pulsed laser sources allowed to explore vibrational features with complex techniques based on nonlinear optical interactions, among which is stimulated Raman scattering (SRS). Building on its combined spectral–temporal resolutions and high chemical sensitivities, SRS has been largely applied as a probe for ultrafast, time‐resolved studies, as well as an imaging technique in biological systems. By using a frequency tunable, narrowband pump pulse jointly with a femtosecond white light continuum to initiate the SRS process, here we measure the Raman spectrum of a prototypical heme‐protein, namely deoxy myoglobin, under two different electronic resonances. The SRS results are compared with the spontaneous Raman spectra, and the relative advantages, such as the capability of our experimental approach to provide an accurate mapping of Raman excitation profiles, are discussed.

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Section: Introductionmentioning

confidence: 99%

Resonant broadband stimulated Raman scattering in myoglobin

Ferrante

Batignani

Fumero

et al. 2018

J Raman Spectroscopy

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“…By controlling the photon energy and the time delay between the XUV pulses, it is possible in principle to excite and select a particular state in the molecule and track the nuclear dynamics with the probe pulse, with the advantage of avoiding strong-field effects or multiphoton excitations. This opens the possibility of studying nonadiabatic effects at conical intersections [19], imaging or clocking nuclear wave packets [20,21], and exploring isomerization processes [17,22,23]. Moreover, the generation of two XUV pulses with table-top sources is also possible, by using high-order high-harmonic generation (HHG) [24].…”

Section: Introductionmentioning

confidence: 99%

Ultrafast x-ray-induced nuclear dynamics in diatomic molecules using femtosecond x-ray-pump–x-ray-probe spectroscopy

et al. 2016

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The capability of generating two intense, femtosecond x-ray pulses with a controlled time delay opens the possibility of performing time-resolved experiments for x-ray-induced phenomena. We have applied this capability to study the photoinduced dynamics in diatomic molecules. In molecules composed of low-Z elements, K-shell ionization creates a core-hole state in which the main decay mode is an Auger process involving two electrons in the valence shell. After Auger decay, the nuclear wave packets of the transient two-valence-hole states continue evolving on the femtosecond time scale, leading either to separated atomic ions or long-lived quasibound states. By using an x-ray pump and an x-ray probe pulse tuned above the K-shell ionization threshold of the nitrogen molecule, we are able to observe ion dissociation in progress by measuring the time-dependent kinetic energy releases of different breakup channels. We simulated the measurements on N 2 with a molecular dynamics model that accounts for K-shell ionization, Auger decay, and the time evolution of the nuclear wave packets. In addition to explaining the time-dependent feature in the measured kinetic energy release distributions from the dissociative states, the simulation also reveals the contributions of quasibound states.

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“…To observe electron dynamics in experiments, several measurements have already been proposed: time-resolved Auger spectra [36], photoelectron angular distributions [10], x-ray absorption [37,38], and x-ray raman [39] spectra. Such experiments would allow the observation of the decoherence of electron dynamics that we predict and thereby test the limits of the current theoretical understanding.…”

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confidence: 99%

Electron Dynamics upon Ionization of Polyatomic Molecules: Coupling to Quantum Nuclear Motion and Decoherence

et al. 2017

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Knowledge about the electronic motion in molecules is essential for our understanding of chemical reactions and biological processes. The advent of attosecond techniques opens up the possibility to induce electronic motion, observe it in real time, and potentially steer it. A fundamental question remains the factors influencing electronic decoherence and the role played by nuclear motion in this process. Here, we simulate the dynamics upon ionization of the polyatomic molecules paraxylene and modified bismethylene-adamantane, with a quantum mechanical treatment of both electron and nuclear dynamics using the direct dynamics variational multiconfigurational Gaussian method. Our simulations give new important physical insights about the expected decoherence process. We have shown that the decoherence of electron dynamics happens on the time scale of a few femtoseconds, with the interplay of different mechanisms: the dephasing is responsible for the fast decoherence while the nuclear overlap decay may actually help maintain it and is responsible for small revivals. DOI: 10.1103/PhysRevLett.118.083001 Electronic motion initiates specific rearrangements of atoms in molecules that are responsible for chemical reactions and biological processes. Because of the advent of attosecond techniques [1,2], it is possible to induce electron dynamics in molecules. Observing and potentially steering electronic motion on its natural time scale may provide novel pathways towards controlling chemical processes [3][4][5][6][7][8]. Since the electron distribution is usually considered to be changing much faster than the nuclear geometry, many theoretical studies treat molecular electron dynamics upon ionization as a purely electronic process, at a single static nuclear geometry [9][10][11][12]: long-lived oscillatory charge migration is then predicted. The fixed-nuclei and single-geometry approximations have however limited validity [13][14][15][16][17][18][19]. The fundamental challenge is to understand to what extent the electronic wave packet retains its coherence, i.e., how long the oscillations in the electronic density survive, in the presence of interactions with the nuclear degrees of freedom.Using a semiclassical description for the coupled systembath evolution, Fiete and Heller identified three processes that contribute to decoherence of the quantum system [20]: (i) system wave packet displacement, (ii) bath overlap decay, and (iii) phase jitter. In the context of molecular electron dynamics, the "system" consists of the electrons and the "bath" of the nuclei. The three mechanisms above can respectively be interpreted as (i) change in the electronic state populations, (ii) decrease of the overlap between the nuclear wave packets on different electronic states, and (iii) dephasing of the different wave packet components. The importance of these mechanisms on the coherent electron dynamics upon molecular ionization remains an outstanding question, that we aim to address in the present Letter.Previous works showed that the n...

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Catching Conical Intersections in the Act: Monitoring Transient Electronic Coherences by Attosecond Stimulated X-Ray Raman Signals

Cited by 155 publications

References 45 publications

Resonant broadband stimulated Raman scattering in myoglobin

Resonant broadband stimulated Raman scattering in myoglobin

Ultrafast x-ray-induced nuclear dynamics in diatomic molecules using femtosecond x-ray-pump–x-ray-probe spectroscopy

Electron Dynamics upon Ionization of Polyatomic Molecules: Coupling to Quantum Nuclear Motion and Decoherence

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