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Science 288 (2000) pp. 1399-1402

Dimensionality effects in the lifetime of surface states

J. Kliewer

2. Physikalisches Institut, RWTH Aachen, D-52056 Aachen, Germany

R. Berndt

2. Physikalisches Institut, RWTH Aachen, D-52056 Aachen, Germany
and
Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany

E.V. Chulkov, V.M. Silkin and P.M. Echenique

Departamento de Física de Materiales, Facultad de Química, Universidad del Pais Vasco
and
Centro Mixto UPV-CSIC and Donostia International Physics Center, Apdo. 1072, 20080 San Sebastian/Donostia, Spain

S. Crampin

Department of Physics, University of Bath, BA2 7AY, United Kingdom

Abstract
A long standing discrepancy between measured and calculated values for the lifetimes of holes in the surface state electron bands on noble metal surfaces is resolved, with both found to have been in error. The ability of the scanning tunneling microscope to verify surface quality before taking spectroscopic measurements is exploited to remove the effects of defect scattering on experimental lifetimes, found to have been a significant contribution to prior determinations. A new theoretical treatment of inelastic electron-electron scattering is developed which explicitly includes hitherto ignored intra-band transitions within the surface state band. The new physical picture to emerge has two-dimensional decay channels dominating the electron-electron interactions that contribute to the hole decay, screened by both s-p and d electron states of the underlying three-dimensional electron system.