INVERSION OF THE CORE LEVEL SHIFT BETWEEN SURFACE AND SUBSURFACE ATOMS OF THE IRIDIUM (100)(1 X-1) AND (100)(5 X-1) SURFACES

In contrast to what is commonly accepted, electronic structure calculations show that the core levels (S1, S2) associated with the surface and first underlayer atoms can be displaced in opposite directions in energy with respect to the bulk level (B). This is fully confirmed by experiments performed on the 4f7/2 level of the Ir(100) surface, both in the unreconstructed (1 x 1) and reconstructed (5 x 1) case.