Summary Abstract: A theoretical study of the effect of lateral interactions on molecular adsorption and desorption

Abstract

The effect of lateral interactions between coadsorbed molecules on adsorbate island growth and the kinetics of adsorption and desorption have been studied within the constraints of a lattice gas model incorporating a combination of deterministic rate equations with a stochastic formulation. The adsorption and desorption of molecular nitrogen on Ru(001) has been investigated in detail. Recent experiments performed at 77 K reveal an unusual functional dependence of the probability of adsorption which displays a maximum at a coverage of approximately 0.2 monolayer [1,2]. EEL spectra indicate chemisorption of molecular nitrogen occurs only at atop sites with the molecular axis oriented perpendicular to the surface plane [2]. Saturation coverage is achieved at approximately 0.5 monolayer [1,2]. Thermal desorption spectra suggest the presence of two distinct chemisorption states at coverages greater than 0.25 monolayer. Quantitative agreement between calculated and experimental thermal desorption spectra as well as the coverage-dependent probability of adsorption is obtained.

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