BONDING OF AN ISOLATED K ATOM TO A SURFACE - EXPERIMENT AND THEORY

We present a new and general technique with which the local properties of the unoccupied states of an adsorbed alkali atom in the low covera ge limit can be studied. The method, based on a combination of experim ental core level spectroscopy data and calculations, is demonstrated f or the K/graphite system. We show that con excitation and decay spectr a of adsorbed Ar combined with the calculations form a most powerful t ool in order to determine the unoccupied density of states for an isol ated K adatom. We iind that the 4s level of an isolated K atom on grap hite is placed 2.7 eV above E-F, With a hybridization width of the ord er of only 0.1 eV.