Thermal and surface core-electron binding-energy shifts in metals

D. M. Riffe, G. K. Wertheim, D. N. E. Buchanan, and P. H. Citrin
Phys. Rev. B 45, 6216 – Published 15 March 1992
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Abstract

High-resolution photoemission spectra from the shallow core levels of alkali metals and of In have been obtained between 78 K and room temperature. The data yield values for the alkali-metal surface-atom core-level shift and show thermal shifts of comparable size for bulk and surface. The positive surface shifts are due to the spill-out of conduction-electron charge, which is responsible for the surface dipole layer. The surface shifts are in good agreement with values obtained from a Born-Haber cycle expressed in terms of surface energies. The thermal shifts are proportional to the lattice expansion, and arise from both initial-state and final-state effects. As the lattice expands, the Fermi level decreases, decreasing the core-electron binding energy. At the same time, the expansion of the conduction-electron charge increases rs, thereby decreasing the potential at the core level and increasing the binding energy. The expansion also decreases the relaxation energy, further increasing the core-electron binding energy. In the alkali metals, the combined potential- and relaxation-energy terms dominate the Fermi-level term, making the shifts positive. In divalent metals the three terms tend to cancel, while in trivalent metals it is the Fermi-level term that dominates, making the shifts negative.

  • Received 31 October 1991

DOI:https://doi.org/10.1103/PhysRevB.45.6216

©1992 American Physical Society

Authors & Affiliations

D. M. Riffe, G. K. Wertheim, D. N. E. Buchanan, and P. H. Citrin

  • AT&T Bell Laboratories, Murray Hill, New Jersey 07974-0636

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Issue

Vol. 45, Iss. 11 — 15 March 1992

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