The Configuration Interaction (CI) Satellites in the 4s--4p Photoelectron Spectra of Cesium Metal and Cesium Overlayers

The 4p spectrum of cesium has been recorded for Cs adsorbed with or without carbon monoxide on nickel and for a thick Cs film. The results are compared with those for CsI. It is demonstrated that apart from the appearance of plasmon excitations in the multilayers the satellite structures are rather similar for the different situations. This behavior appears to be different from that of xenon and iodine and the difference can be explained by a stronger localisation of the 4f orbitals in the presence of a 4d exp --2 double hole for Cs. The satellites are compared with theoretical and experimental results from the literature. The two main satellites at 9.3 and 11.3 eV relative binding energy are related to corresponding satellites for barium.