ANOMALOUS BRANCHING RATIO OF THE CS 4D DOUBLET IN SUBMONOLAYER DEPOSITIONS

High-resolution Cs 4d core-level spectra were performed by photoemissi on spectroscopy at photon energies h nu=108-115 eV. At room temperatur e, for submonolayer metal deposition on a Ge(100) surface, a nonstatis tical branching ratio Cs 4d(5/2):4d(3/2) was obtained. Its value was f ound close to 4/3 instead of the usual 3/2. Conversely, Cs 4d spectra performed on a thick metal layer presented two components, the first d ue to the surface and the other to the bulk; in this case, only the su rface component was affected by a nonstatistical spin-orbit ratio. A p ossible explanation of this effect is discussed with reference to the relativistic random-phase approximation accounting for a similar effec t in Xe.