Picosecond time-resolved adsorbate response to substrate heating: Spectroscopy and dynamics of CO/Cu(100)

Germer, Thomas A.; Stephenson, John C.; Heilweil, Edwin J.; Cavanagh, Richard R.

doi:10.1063/1.467792

Cited by 131 publications

(102 citation statements)

References 64 publications

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“…This conclusion differs from that of Lewis et al, who applied their high coverage damping formula ͑valid for the q‫0؍‬ mode͒ to study the adsorbate-substrate energy transfer for CO on Cu͑111͒, in response to ultrafast laser heating of the substrate. 12 In this paper we generalize the results presented above to adsorbates of arbitrary size ͑but treated as rigid objects͒, which is relevant for, e.g., ''large'' hydrocarbons. We also discuss the influence of adsorbate-adsorbate interactions of a nonphononic nature, i.e., not mediated by the substrate phonons, on the damping rate.…”

Section: Introductionmentioning

confidence: 69%

Low-frequency adsorbate vibrational relaxation and sliding friction

et al. 1999

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We present a study of the damping ͑energy relaxation͒ of low-frequency adsorbate vibrational modes via one-phonon emission. The dependence of the damping rate on the size of the adsorbates, the adsorbate coverage, and the nature of the ͑nonphononic͒ adsorbate-adsorbate interactions has been studied. We show that different experimental probing techniques, e.g., inelastic helium scattering or time-resolved adsorbate response to substrate heating, probe different damping rates. We also show that the energy relaxation rate may be strongly affected by ͑pure͒ dephasing processes. Experimental data are presented and compared to the theoretical results. Finally, we show that the phononic friction vanishes for incommensurate layers sliding on solid surfaces and present a discussion about the nature of the surfaces used in recent measurement of the sliding friction on superconducting lead surfaces. ͓S0163-1829͑99͒07417-2͔

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Section: Introductionmentioning

confidence: 69%

Low-frequency adsorbate vibrational relaxation and sliding friction

et al. 1999

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“…2. The onset of the peak shift at negative delay is not a violation of causality, but rather a consequence of the detection scheme caused by the perturbed free-induction decay [14]: The polarization that is induced by the IR pulse decays with T 2 1.16 ps. The effect of the pump pulse can therefore be seen already at negative delay times, when the decaying polarization is perturbed by it.…”

Section: Femtosecond Surface Vibrational Spectroscopy Of Co Adsorbed mentioning

confidence: 99%

Femtosecond Surface Vibrational Spectroscopy of CO Adsorbed on Ru(001) during Desorption

et al. 2000

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Using time-resolved sum-frequency generation spectroscopy, the C-O stretch vibration of carbon monoxide adsorbed on a single-crystal Ru(001) surface is investigated during femtosecond near-IR laser excitation leading to desorption. A large transient redshift, a broadening of the resonance, and a strong decrease in intensity are observed. These originate from coupling of the C-O stretch to low-frequency modes, especially the frustrated rotation, that are highly excited in the desorption process. PACS numbers: 68.35.Ja, 33.70.Jg, 78.47. + p, 82.20.Rp The dynamics of the interaction between molecules and metal surfaces is of fundamental importance in surface science, since these determine key physical and chemical properties-essential in, e.g., catalysis-such as energy transfer and molecular reactivity [1] [6] at surfaces. These experiments were limited to temperatures below those at which desorption of the adsorbate occurs. However, when one is interested in surface reactions, the more relevant situation occurs at higher temperatures, where higher-lying vibrational modes get thermally occupied that play an important role in the surface chemistry.We present here femtosecond time-resolved vibrational sum-frequency generation (fs-SFG) spectra of CO molecules adsorbed on a Ru(001) surface, taken while a significant number (ϳ50%) of these molecules is desorbing due to fs laser excitation. With this fs-SFG method, snapshots of the (C-O) stretch vibration can be taken, under conditions where desorption is occurring (at lattice temperatures transiently exceeding the desorption temperature by over 500 K), shedding new light on the dynamics of the desorption process and the coupling of vibrational modes at the surface.The experiments were carried out in an ultrahigh vacuum chamber (base pressure 1 3 10 210 mbar) equipped with standard surface science tools. Our commercial laser system produces 800 nm, 110 fs pulses of 4.5 mJ͞pulse at 400 Hz, chopped down to 20 Hz for these experiments. One-third of the energy is used to excite the surface ("pump" pulse, typical absorbed fluence 55 J͞m 2 [7]), and the remaining energy is used to pump an optical parametric generator/amplifier (OPG͞OPA) providing tunable (l 2 10 mm, bandwidth ϳ150 cm 21 ) IR pulses with an energy of typically 10 mJ and a duration of 150 fs. The portion of the 800 nm pulse which is not converted into IR in the OPG͞OPA-process is spectrally narrowed down to 4 cm 21 , and is used in the SFG experiments as the visible (VIS) up-conversion pulse. An extensive description of the complete experimental setup as well as the surface cleaning, preparation, and characterization procedures can be found in Ref. [8].The surface sensitivity of SFG relies on the fact that the second-order nonlinear susceptibility is nonvanishing at interfaces [9]. This enables the generation of an electric field E SFG out of two incidents fields E VIS and E IR , where energyhv and parallel momentum k k must be con-For frequencies v IR within the IR bandwidth resonant with the vibrational tra...

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“…Our observation implies either that the lifetime of vðM-CÞ overtones is sufficiently long to be multiply excited, or that the intermode coupling constant with the RC mode allows energy transfer to the RC mode, triggering molecular hopping. Although quantitative information on both the lifetime and intermode coupling constants of vibrationally excited states of CO molecules adsorbed on solid surfaces has been experimentally obtained using infrared absorption spectroscopy (IRAS) measurements [47,48], it remains a challenge to overcome low infrared cross sections of the vðM-CÞ mode and intrinsically poor spectral sensitivity at low-frequency ranges [49]. Alternatively, the intermode coupling between fundamental vibrational modes of a molecule on a solid surface can be investigated by theoretical computations, as demonstrated by Lorente et al [50].…”

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confidence: 99%

Lateral Hopping of CO on Ag(110) by Multiple Overtone Excitation

Lim

Arafune

et al. 2016

Phys. Rev. Lett.

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A novel type of action spectrum representing multiple overtone excitations of the vðM-CÞ mode was observed for lateral hopping of a CO molecule on Ag(110) induced by inelastically tunneled electrons from the tip of a scanning tunneling microscope. The yield of CO hopping shows sharp increases at 261 AE 4 mV, corresponding to the C-O internal stretching mode, and at 61 AE 2, 90 AE 2, and 148 AE 7 mV, even in the absence of corresponding fundamental vibrational modes. The mechanism of lateral CO hopping on Ag (110) was explained by the multistep excitation of overtone modes of vðM-CÞ based on the numerical fitting of the action spectra, the nonlinear dependence of the hopping rate on the tunneling current, and the hopping barrier obtained from thermal diffusion experiments.

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Picosecond time-resolved adsorbate response to substrate heating: Spectroscopy and dynamics of CO/Cu(100)

Cited by 131 publications

References 64 publications

Low-frequency adsorbate vibrational relaxation and sliding friction

Low-frequency adsorbate vibrational relaxation and sliding friction

Femtosecond Surface Vibrational Spectroscopy of CO Adsorbed on Ru(001) during Desorption

Lateral Hopping of CO on Ag(110) by Multiple Overtone Excitation

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