Thermal and Surface Core-Electron Binding-Energy Shifts in Metals

Authors

D. Mark Riffe, Utah State UniversityFollow
G. K. Wertheim
D. N. E. Buchanan
P. H. Citrin

Document Type

Article

Journal/Book Title/Conference

Physical Review B

Volume

45

Issue

11

Publication Date

3-15-1992

First Page

6216

Last Page

6225

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 r_s, 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.

Comments

Published by American Physical Society in Physical Review B. Publisher PDF is available for download through link above.

Recommended Citation

"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 (1992).