Unusual chemisorption structure of Na on Al(111): a SEXAFS study

Abstract

The adsorption of Na on Al(111) has been studied by surface extended X-ray absorption fine structure (SEXAFS) in the coverage range of θNa = 0.16-0.7 monolayer at room temperature. For θNa = 0.16–0.33, Na atoms occupy an unusual 6-fold coordinate site formed by displacing every third (θNa = 0.33) Al atom in the first layer of the substrate. The NaAl bond length is 3.31 Å, independent of coverage, consistent with metallic bonding. These results have important implications for models of alkali metal adsorption.