Indication of non-thermal contribution to visible femtosecond laser-induced CO oxidation on Ru(0001)

Öberg, Henrik; Gladh, Jörgen; Marks, Kess; Ogasawara, Hirohito; Nilsson, Anders; Pettersson, Lars G. M.; Öström, Henrik

doi:10.1063/1.4928646

Cited by 16 publications

(48 citation statements)

References 59 publications

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“…The CO 2 :CO yield ratio is around 1:35 independent of fluence. This exponent and yield ratio are identical within error bars to the values obtained with 800 nm laser excitation, 42,47 where CO oxidation and desorption were found to be substrate mediated and driven by hot substrate electrons (oxidation) and phonons (desorption). We note a seeming difference in substrate-mediated yields when exciting below and on resonance, but for the CO 2 yield [Figs.…”

Section: Resultssupporting

confidence: 81%

“…8,18,19,[43][44][45]57 Two-pulse correlation (2PC) measurements using optical laser pulses have been reported earlier and used to discriminate between hot-electron-driven and thermally activated oxidation of CO on Ru(0001). 42,47 Here we exploit the availability of the novel double-pulse scheme to explore the feasibility of 2PC measurements in the X-ray regime. A target for future experiments with variable pulse separation would, e.g., be a direct determination of the lifetime of the double valence-hole state.…”

Section: Resultsmentioning

confidence: 99%

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Atom-specific activation in CO oxidation

Schreck

Diesen

LaRue

et al. 2018

The Journal of Chemical Physics

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We report on atom-specific activation of CO oxidation on Ru(0001) via resonant X-ray excitation. We show that resonant 1s core-level excitation of atomically adsorbed oxygen in the co-adsorbed phase of CO and oxygen directly drives CO oxidation. We separate this direct resonant channel from indirectly driven oxidation via X-ray induced substrate heating. Based on density functional theory calculations, we identify the valence-excited state created by the Auger decay as the driving electronic state for direct CO oxidation. We utilized the fresh-slice multi-pulse mode at the Linac Coherent Light Source that provided time-overlapped and 30 fs delayed pairs of soft X-ray pulses and discuss the prospects of femtosecond X-ray pump X-ray spectroscopy probe, as well as X-ray twopulse correlation measurements for fundamental investigations of chemical reactions via selective X-ray excitation.

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Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Atom-specific activation in CO oxidation

Schreck

Diesen

LaRue

et al. 2018

The Journal of Chemical Physics

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“…For example, this system was the subject of experimental investigations on FL induced desorption [6][7][8], FL induced formation of "hot" adsorbates [8,9], adsorbate diffusion on the surface [9], recombinative desorption of CO from C/O coadsorbates [10], as well as FL induced oxidation (to CO 2 ) and desorption (of CO) of CO/O coadsorbates [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Femtosecond-laser induced dynamics of CO on Ru(0001): Deep insights from a hot-electron friction model including surface motion

et al. 2016

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A Langevin model accounting for all six molecular degrees of freedom is applied to femtosecond-laser induced, hot-electron driven dynamics of Ru(0001)(2 × 2):CO. In our molecular dynamics with electronic friction approach, a recently developed potential energy surface based on gradient-corrected density functional theory accounting for van der Waals interactions is adopted. Electronic friction due to the coupling of molecular degrees of freedom to electron-hole pairs in the metal are included via a local density friction approximation, and surface phonons by a generalized Langevin oscillator model. The action of ultrashort laser pulses enters through a substrate-mediated, hot-electron mechanism via a time-dependent electronic temperature (derived from a two-temperature model), causing random forces acting on the molecule. The model is applied to laser induced lateral diffusion of CO on the surface, "hot adsorbate" formation, and laser induced desorption. Reaction probabilities are strongly enhanced compared to purely thermal processes, both for diffusion and desorption. Reaction yields depend in a characteristic (nonlinear) fashion on the applied laser fluence, as well as branching ratios for various reaction channels. Computed two-pulse correlation traces for desorption and other indicators suggest that aside from electron-hole pairs, phonons play a non-negligible role for laser induced dynamics in this system, acting on a surprisingly short time scale. Our simulations on precomputed potentials allow for good statistics and the treatment of long-time dynamics (300 ps), giving insight into this system which hitherto has not been reached. We find generally good agreement with experimental data where available and make predictions in addition. A recently proposed laser induced population of physisorbed precursor states could not be observed with the present low-coverage model.

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“…The elevated energy and vibration of the TNI make the excited adsorbate molecule to easily overpass the energy saddle point along the dissociation reaction, leading to an efficient dissociation (right, Figure A). Besides the stretching motion, the energy carried by the hot electron can also be coupled to other vibrational modes, such as frustrated rotation mode, which plays an important role in altering the orientation of the chemical bond. The distribution of the energy carried by the hot electron among the vibrational modes during the adsorbate activation process can be studied by analyzing the intermediate states with ultrafast spectroscopy and the DFT calculations .…”

Section: Activation Of Adsorbates With Received Hot Electronsmentioning

confidence: 99%

Quantum‐Sized Metal Catalysts for Hot‐Electron‐Driven Chemical Transformation

Wei

Sun

2018

Advanced Materials

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Hot-electron-driven chemical transformation (HEDCT) represents an emerging research area in utilizing photoresponsive nanoparticles to enable efficient solar-to-chemical conversion. The unique properties of quantum-sized metal nanoparticles (QSMNPs) make them a class of photocatalysts that can generate hot electrons to drive surface chemical reactions with high quantum efficiency. Compared to the conventional thermal-driven chemical reactions, HEDCT offers the advantages of accelerating reaction rate, improving reaction selectivity, and possibly enabling the occurrence of thermodynamically endergonic reactions. Despite its embryonic stage of development, using QSMNPs for HEDCT shows great promise. Herein, a timely overview on the research progress is provided with a focus on the fundamental quantum processes involved in the photoexcitation of hot electrons and the following HEDCT on the surface of QSMNPs. The last section discusses the challenges, which also represent the opportunities for the materials research community, in designing robust QSMNP photocatalysts and understanding the fundamental quantum phenomena in HEDCT.

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Indication of non-thermal contribution to visible femtosecond laser-induced CO oxidation on Ru(0001)

Cited by 16 publications

References 59 publications

Atom-specific activation in CO oxidation

Atom-specific activation in CO oxidation

Femtosecond-laser induced dynamics of CO on Ru(0001): Deep insights from a hot-electron friction model including surface motion

Quantum‐Sized Metal Catalysts for Hot‐Electron‐Driven Chemical Transformation

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