Surface Core Level Shift: High Sensitive Probe to Oxygen-Induced Reconstruction of Rh(100)

Oxygen-induced Rh3d(5/2) surface core level shifts were used to probe the local electronic structure of first layer Rh atoms in the (2 x 2)pg reconstructed phase formed upon oxygen adsorption. By comparison of the computed shifts for differently reconstructed geometries with the experimental shifts obtained from high-energy resolution photoemission measurements, we confirm that the reconstructed phase is formed by Rh atoms single- and double-bonded to oxygen, yielding a shift from the bulk component of -185 and +140 meV, respectively. We find that the core level shifts are affected by the local rhomboidal distortion of the surface lattice, Moreover, we show that, on Rh(100), the oxygen-induced surface core level shifts are dominated by initial state effects and proportional to the calculated shift of the d-band center. The latter is therefore correlated to the local surface chemical reactivity, as already found for other adsorbate systems on transition metals.