SURFACE CORE-LEVEL SHIFTS IN LIQUID-METALS AND ALLOYS

Surface core level shifts in liquid metals and alloys have been observ ed for the first time by photoelectron spectroscopy. In liquid Cs, the 5p3/2 core line is shifted by 224 +/- 5 meV to higher binding energy, in close agreement with the corresponding value found in solid Cs. In Au-Ga alloys, the surface induced core level shifts have been analyze d at both the Au and Ga sites in the liquid and solid state. Marked ch anges in the relative intensities of the surface shifted core lines on melting are observed. The present results strongly support the pictur e of well defined atomic layers on top of a liquid metal, similar to t he crystalline case with a first atomic layer exhibiting electronic su rface properties and a second layer revealing basically bulk behaviour .