Phonon- Versus Electron-Mediated Desorption and Oxidation of CO on Ru(0001)

Bonn, Mischa; Funk, Stephan; Heß, Christian; Denzler, Daniel N.; Stampfl, Catherine; Scheffler, Matthias; Wolf, Martin; Ertl, G.

doi:10.1126/science.285.5430.1042

Cited by 451 publications

(400 citation statements)

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“…Such extreme electron correlation can be attributed to ineffective screening of the Coulomb interaction and resembles electron relaxation processes in molecular materials such as C 60 and carbon nanotubes rather than metals [28,87]. In metals, where the Coulomb interaction is more strongly screened and the photoexcited carrier density is only a small fraction of the Fermi-level density [38], reaching comparable T e requires about 100-times-larger fluences and electron thermalization takes about 10 times longer [67,73,94,95].…”

Section: Discussionmentioning

confidence: 99%

“…The ultrafast scattering processes that lead to thermionic emission obliterate information in mPP spectra on the electronic bands and dipole transitions through which the primary excitation occurred. The nearly instantaneous augmentation of the free carrier density above about 10 19 cm −3 at the Fermi level alters the chemical and physical properties of graphite [34,[73][74][75][76]. In particular, we propose that the reported transformation of sp 2 graphite to sp 3 diamond under femtosecond laser excitation [34,[74][75][76][77] occurs by a photoinduced electronic phase transition: The redistribution of electrons from the π bands with bonding character to the unoccupied ILB causes the lattice instability.…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast Multiphoton Thermionic Photoemission from Graphite

et al. 2017

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Electronic heating of cold crystal lattices in nonlinear multiphoton excitation can transiently alter their physical and chemical properties. In metals where free electron densities are high and the relative fraction of photoexcited hot electrons is low, the effects are small, but in semimetals, where the free electron densities are low and the photoexcited densities can overwhelm them, the intense femtosecond laser excitation can induce profound changes. In semimetal graphite and its derivatives, strong optical absorption, weak screening of the Coulomb potential, and high cohesive energy enable extreme hot electron generation and thermalization to be realized under femtosecond laser excitation. We investigate the nonlinear interactions within a hot electron gas in graphite through multiphoton-induced thermionic emission. Unlike the conventional photoelectric effect, within about 25 fs, the memory of the excitation process, where resonant dipole transitions absorb up to eight quanta of light, is erased to produce statistical Boltzmann electron distributions with temperatures exceeding 5000 K; this ultrafast electronic heating causes thermionic emission to occur from the interlayer band of graphite. The nearly instantaneous thermalization of the photoexcited carriers through Coulomb scattering to extreme electronic temperatures characterized by separate electron and hole chemical potentials can enhance hot electron surface femtochemistry, photovoltaic energy conversion, and incandescence, and drive graphite-to-diamond electronic phase transition.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ultrafast Multiphoton Thermionic Photoemission from Graphite

et al. 2017

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“…For example, inelastic nonequilibrium electrons tunneling at metal/ molecule interfaces plays a crucial role in catalysis 11 and molecular electronics. 12,13 More specifically, the dynamical behavior of nonequilibrium electrons (NEs) governs the yield of hot electron-mediated surface reactions on metal surfaces.…”

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confidence: 99%

Hot Adsorbate-Induced Retardation of the Internal Thermalization of Nonequilibrium Electrons in Adsorbate-Covered Metal Nanoparticles

Bauer

Abid

2006

J. Phys. Chem. B

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Femtosecond transient absorption spectroscopy has been used to investigate the electron-electron scattering dynamics in sulfate-covered gold nanoparticles of 2.5 and 9.2 nm in diameter. We observe an unexpected retardation of the absolute internal thermalization time compared to bulk gold, which is attributed to a negative feedback by the vibrationally excited sulfate molecules. These hot adsorbates, acting as a transient energy reservoir, result from the back and forth inelastic scattering of metal nonequilibrium electrons into the π* orbital of the sulfate. The vibrationally excited adsorbates temporarily govern the dynamical behavior of nonequilibrium electrons in the metal by re-emitting hot electrons. In other terms, metal electrons reabsorb the energy deposited in the hot sulfates by a mechanism involving the charge resonance between the sulfate molecules and the gold NPs. The higher surface-to-volume ratio of sulfate-covered gold nanoparticles of 2.5 nm leads to a stronger inhibition of the internal thermalization. Interestingly, we also note an analogy between the mechanism described here for the slow-down of electron-electron scattering in metal nanoparticles by the hot adsorbates and the hot phonon-induced retardation of hot charge carriers cooling in semiconductors.Hybrid nanostructured materials can be seen as complex systems, which lie at the border of solid-state physics and supramolecular chemistry. Metal nanoparticles (NPs) protected with functional molecules can give a unique opportunity to investigate the coupling between electron transport dynamics and molecular structural changes beyond the Born-Oppenheimer approximation.As the size decreases to the nanoscale range (shorter than the electron mean free path), the electronic properties of the metal can fall under the influence of surface molecular species. For example, evidence appeared that adsorbates can modify the electronic properties of small metal nanoparticles 1-4 (below 20 nm) by decreasing the surface plasmon lifetimes. This additional damping channel, which leads to a homogeneous broadening of the surface plasmon band, is called chemical interface damping, i.e., metal electrons tunnel back and forth into empty electronic states of adsorbates. [5][6][7] The electronic structure of the gold/sulfate interface consists of a σ donation and a σ* and π* back-donation mechanism: The occupied σ orbitals of the sulfate give charge to the metal, while the unoccupied σ* and π* orbitals accept charge from the metal. 8 A key characteristic of the present system is the coupling between gold electrons and sulfate vibrations via the partial occupation of the sulfate π* orbital by the gold electrons. This charge resonance leads to a strong chemical interface damping of the surface plasmon as revealed by the nonclassical broadening of the surface plasmon band. 9 Thus, under equilibrium conditions, sulfate molecules affect the electronic properties of the gold nanoparticles by opening an additional damping channel for the surface plasmon. The next step w...

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“…We observe spectral changes on two different time scales that can be connected with the dynamics of electrons and phonons in the metal substrate. Photo-induced reactions at metal surfaces are typically substrate mediated since the substrate absorbs the light much more efficiently than a single adsorbate layer [23][24][25]. Hot electrons are excited in the Ru substrate by the fs laser pulse, thermalize within $100 fs [26], and may couple directly to the adsorbate vibrational degrees of freedom to initiate a reaction on a subpicosecond time scale.…”

mentioning

confidence: 99%