Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 100: Surface Dynamics II

O 100.8: Talk

Friday, April 4, 2014, 12:15–12:30, PHY C 213

Vibrational properties of O₂ on Ag(100): multiple adsorption sites vs. Fermi resonances? — Daniel Strobusch, Jörg Meyer, and •Christoph Scheurer — TU München, Garching, Germany

Adsorption of molecular oxygen on the Ag(100) surface is commonly believed to occur competitively on both hollow and bridge sites. A double peak for the oxygen stretch mode observed in high-resolution energy electron loss spectroscopy (HREELS) in combination with semi-empirical cluster calculations [1,2] have been invoked as evidence. However, recent density functional theory (DFT) calculations question this picture [3]. In this work, we propose that side-on adsorption of the oxygen molecule on the fourfold hollow site alone can reconcile the DFT results with the experimentally measured vibrational properties. We calculate the latter with a full quantum dynamical treatment at the vibration configuration interaction (VCI) level of theory [4] based on a six-dimensional DFT potential energy. This yields excellent agreement with the observed overtone and combination bands [2]. Guided and supported by electronic structure calculations, we propose a model based on the occurrence of a Fermi resonance to explain the HREELS double peak and its coverage dependence. We will discuss implications for other surfaces and larger adsorbates.

[1] L. Vattuone et al., Surf. Sci. 377, 671 (1997).

[2] F. Buatier de Mongeot et al., J. Chem. Phys. 106, 9297 (1997).

[3] V. J. Bukas et al., Z. Phys. Chem., 227, 1523 (2013).

[4] D. Strobusch, M. Nest and C. Scheurer, J. Comp. Chem. 34, 1210 (2013).