<title>Surface Atom Core Level Shifts In The Noble Metals</title>

Abstract

Surface atom core level shifts in the noble metalsG. K. Wertheim and P. H. CitrinAT &T Bell LaboratoriesMurray Hill, New Jersey 07974AbstractPhotoemission with characteristic x -ray and synchrotron radiation has shown that thefirst atomic layers of the noble metals have electronic properties which differ from thoseof the bulk. The d bands are narrowed at the surface, resulting in reduced s -d hybridiza-tion and a transfer of charge from s- into d- states. These changes result in a decrease inthe core electron binding energies at the surface which have been determined for all threemetals.IntroductionAlthough it was generally believed on the basis of theoretical arguments that surfaceatoms must have electronic properties distinguishable from those of the bulk, the experi-mental verification of this fact presented unexpected difficulty. Only during the pastfive years have the electronic properties of the first atomic layers of metals beenrevealed by photoemission spectroscopy. There were two basic basic problems: (1) Theinstrumental resolution available in core electron spectroscopy was typically no betterthan 0.5 eV, a value comparable to the largest of the shifts which were subsequentlydiscovered.