Bonding between alkali atoms and metal substrates probed by soft-x-ray emission

We have studied the bonding of K and Cs to Ni and Cu metal surfaces by examining the soft-x-ray emission from the K 3p and Cs 5p core holes. The localization of the core hole allows a measurement of the coverage dependence of the valence states specifically associated with the alkali atom. The energy distribution of these states shows, certainly in the case of Ni, that the substrate dz2 state plays a non-negligible role in the chemical bonding. Further for Ni, the quasi-two-dimensional metalization of the alkali overlayers was clearly observed