In equation 2 , it was assumed that the substrate temperature T s at the interface is constant during the experiment. Frischkorn C J. Hrbek J J. Sign up for new issue notifications. Depending on the coupling scenario, T ads t follows mainly either the electron temperature T el or the phonon temperature T ph.

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Hammer B Surf. However, after electron thermalization i. Chen G Thermal conductivity and ballistic-phonon transport in the cross-plane windos of superlattices Phys. However, one has to keep in mind that this vibrational damping of the nascent N 2 molecule relates to locations on the ground state PES beyond the transition state, whereas the nonadiabatic coupling in the excitation step of the fs-laser induced Gx-ru001 association corresponds to the ascending side of the desorption barrier.

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Redhead P Vacuum 12 Crossref. As described above, in a substrate-mediated surface reaction, each of the substrate’s subsystems, electrons and phonons, can couple to the reactants in the adsorbate layer independently. Thus, one might very well expect nonadiabatic effects to play a significant role also in the femtosecond fs -laser-induced associative desorption of CO from Ru To quantify the efficiency of the laser-induced process, the CO desorption yield is measured in series of laser shots impinging the same spot on the adsorbate-covered Ru sample.

It has a worldwide membership of around 50 comprising physicists from all sectors, as well as those with an interest in physics. A 78 Crossref. The Institute of Physics IOP is a leading scientific society promoting physics and bringing physicists together for the benefit of all.

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B Krenzer et al New J. One might expect that due to the location of the barrier along the vibrational coordinate, excitation of the interatomic distance d will facilitate the CO associative desorption more than it does excitation of the distance coordinate z between the C—O and the Ru surface.

Calculations are performed for three frictional coupling scenarios with parameter sets A, B and C and the results are plotted with solid, dashed and dotted lines, respectively. This means that despite the seemingly qualitative agreement in the fluence dependence and two-pulse correlation, no quantitative agreement is found for a purely phonon-driven energy transfer. However, the experimentally measured values of the thermal boundary conductance were up to two orders of magnitude larger than expected from the two models.

Quantitative details will be discussed further below. Heat Transfer 37 Crossref.

Furthermore, such an ultrafast response due to nonadiabatic coupling should in principle cause a clear isotope effect, however, in conflict with the yield ratio of unity found in the experiment. It turned out that the values for E a extracted from modelling the experimental data frequently exceed the measured activation energies for desorption, e.

This results in a set of equations analogous to the Fresnel equations wineows optics.

The error originates from the uncertainties in the film thickness and the determination of the time-constant. This site uses cookies. As a consequence, the nascent CO molecule might be trapped and at least partially thermalized or scattered at this chemisorption well losing memory of the initial activation step.

While for an associative desorption process, naturally as a bimolecular reaction, the yield should follow an inverse power law e. In an alternative scenario, the observed wavelength dependence might be explained by different optical properties of the Ru substrate with respect to the two wavelengths applied. Contributions from nonthermalized electrons play—if anything—only a minor role. Possible origins for this deviation are discussed in the following.


The f s are the corresponding complete partition functions.

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Consequently, systems exhibiting dynamical cooling should gd-u001 show a significant decrease of the sticking probability of impinging particles with increasing particle energy. S Wagner et al New J. Most studies on surface femtochemistry have addressed desorption of molecular adsorbates like NO or CO from transition metals e. In this paper, we show that an abrupt, smooth hetero-interface exhibit—even at temperatures higher than the Debye temperature of the heated material—a thermal boundary conductance which is in good agreement but slightly lower than the values predicted by the most basic versions of the AMM and DMM theories.

Frictional parameters of the different reaction scenarios to reproduce the experimental data of the fs-laser-induced CO recombination. Small deviations, especially at low coverages, most likely arise gx-ru001 difficulties in determining the correct ratio between the LT- and HT-TDS peaks in these overlapping TD features.

The theoretical models discussed here assume population equilibrium between all modes.