Introduction

For explaining the available experimental data on the co-adsorption of alkaline metal atoms and gas molecules on metals, a model for the surface atom-gas complex has been proposed by Bonzel.1 This model is based on the transition of electrons from the top surface to CO molecule, and it has been introduced to explain the increasing in adsorption energy in Fe + K catalysis.2'3 The potassium adsorbed on the Pt(111) surface decreases the work function. Due to a local change of the work function45 on alkali adsorption, one can also expect a strong local effect of alkali on the gas chemisorptions.

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Lamoen6 has been performed electronic structure calculations of the interaction of the potassium and the oxygen with the graphite (GR), individually and as well co-adsorbate. The authors show that at low coverage the potassium graphite bond is largely ionic and the variation of the K-GR bond energy with the lateral position of the K atom in the graphite unit cell is very small. On the clean surface the O2-GR interaction is found to be repulsive in accordance with the extremely low sticking coefficient observed for O2 on clean graphite. When potassium is adsorbed on the graphite surface, O2 chemisorbs at the potassium-covered surface. The energy barrier towards dissociation of O2 on the clean graphite surface is estimated to be similar to that of the gas phase O2. Authors find that for O2 on K-GR the barrier for dissociation is much smaller than in the gas phase or on the clean graphite surface.

The potential ionisation of thulium atoms is more than the work function of graphite and it can be expected that local change of work function of graphite at adsorption of atoms Tm will be less than the same for K atoms. We are studying the reaction between CsCl molecules with Tm atoms at co-adsorption of these particles on 2DGF on Re with the aim to research the role of potential ionisation of atoms in the interaction on the surface. It is possible to expect, that products of CsCl + Tm reaction will allow defining the valence of Tm in the adsorbed condition. It was informed about the possible change of the valence of atoms of rare earth elements at adsorption on transitive metals.7

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