Switching from molecular to dissociative adsorption with vibrational energy: ethylene on Ag(001)

Vattuone, L.; Savio, Letizia; Valbusa, U.; Rocca, M.

doi:10.1016/s0009-2614(00)01224-0

Cited by 18 publications

(20 citation statements)

References 30 publications

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“…Ethylene adsorption at Ag surfaces [3,4] is particularly important for the understanding of the so-far unsolved ethylene epoxidation reaction [5][6][7][8] for which surface defects might play a pivotal role. This paper follows our previous investigations of C 2 H 4 adsorption on Ag(100) and Ag(410) [9][10][11][12][13][14][15]. In these experiments we demonstrated that physisorbed and π-bonded states exist on Ag(100) and are characterized by a different adsorption energy [9] and by a different C 1s photoemission signature [11].…”

Section: Introductionsupporting

confidence: 84%

Coverage dependence of the dynamics of ethylene adsorption on Ag(210)

Vattuone

Savio

Rocca

2004

J. Phys.: Condens. Matter

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The sticking probability of C 2 H 4 on Ag (210) is studied by the molecular beam technique and by high resolution electron energy loss spectroscopy. At a crystal temperature of 110 K, adsorption occurs initially into a stable, π-bonded, state. At larger coverage a metastable state is populated, too. The sticking probability, S, decreases with increasing translational energy indicating nonactivated adsorption. At low coverage and for impact angles from −60• to +60• , S is angle independent, decreasing only as soon as the (100) nanofacets start to be shadowed. At higher coverage, in contrast, S depends on the impact angle, decreasing markedly for grazing incidence onto the (100) nanoterraces. The saturation coverage corresponds to quarter occupancy of the available step sites.

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Section: Introductionsupporting

confidence: 84%

Coverage dependence of the dynamics of ethylene adsorption on Ag(210)

Vattuone

Savio

Rocca

2004

J. Phys.: Condens. Matter

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“…Excluding an effect of pyrolysis also for the longer exposure is less straightforward. We notice however that the changes in the HREEL spectra occur abruptly above 850 K, 20 while the intensity of masses 26 and 27 increases smoothly with T N . Moreover the intensity of the peak at mass 26 changes by only 1% in the T N range where differences in the HREEL spectra are relevant.…”

Section: Experimental Set-upmentioning

confidence: 70%

Ethylene Adsorption on Clean and Oxygen Covered Flat and Stepped Ag(001)

Vattuone

Savio

Rocca

2003

Int. J. Mod. Phys. B

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In the present paper we review our findings on ethylene adsorption on clean and oxygen covered Ag(001) surfaces investigated by dosing the gas with a Supersonic Molecular Beam and analysing the adsorption state either by High Resolution Electron Energy Loss Spectroscopy or by High Resolution X Rays Photoemission Spectroscopy. The final adsorption state depends on the translational and on the internal energy of the gas-phase molecules and on the presence of defects. At low translational energy ethylene either physisorbs or very weakly chemisorbs at flat terrace sites. The physisorption probability is thereby hindered by rotational excitation. A more strongly bound, π bonded, state forms at higher translational energy, the activation barrier being related to the energy needed to form the relevant defect at which chemisorption takes place. A further even more strongly bound state forms only when dosing vibrationally excited molecules from the gas phase.

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“…The desorption temperature of 140 K is indicative of an adsorption energy, E ads ¼ 0:4 eV/molecule (assuming a prefactor of 1 Â 10 12 Hz). This result is at variance with adsorption at flat Ag(1 0 0) where only physisorption takes place at the lowest E i [17]. The open step provides therefore the non activated chemisorption site for p-bonding [18].…”

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confidence: 84%