Surface core level shift observed on NiAl(110)

Using high resolution core level spectroscopy, a surface core level shift towards lower binding energy of -0.13 eV is determined for the 2p level of the outwardly relaxed Al surface atoms on NiAl(110). Density functional theory based calculations with inclusion of final state effects yield a value of -0.14 eV for this shift in excellent agreement with experiment. We show that the initial state approximation yields a value of +0.09 eV, i.e. the inclusion of final state relaxation effects is vital not only to obtain the correct value but even the correct sign for this shift. (C) 2003 Elsevier Science B.V. All rights reserved.