Parts | Days | Selection | Search | Downloads | Help
M: Metallphysik
M 11: Diffusion und Punktdefekte III
M 11.1: Fachvortrag
Monday, March 26, 2001, 15:15–15:30, S12
Analysis of the core electron momenta of Li, B, C, and O by two detector Doppler broadening spectroscopy — •K. Blaurock1, A. A. Rempel1,2, K. J. Reichle1, W. Sprengel1, and H.-E. Schaefer1 — 1Institut für Theoretische und Angewandte Physik, Universität Stuttgart, 70550 Stuttgart, Germany — 2Institute of Solid State Chemistry, Russian Academy of Sciences, 620219 Ekaterinburg, Russia
A systematic investigation of the 1s core electron (CE) momenta of the elements Li, B, C, and O and its empirical modeling is presented. The two detector technique was used for the measurement of the Doppler broadening of the positron-electron annihilation γ quanta to determine the electron momentum distribution of the atoms surrounding the annihilation site. This technique is very sensitive up to high electron momenta and allows for the analysis of the CE contribution which besides the valence electron (VE) contribution amounts only to 5 % of the data.
The Doppler broadened spectra were analyzed using an empirical model in which the VE component is modeled by an inverted parabola where the cut-off value corresponds to the maximum kinetic energy, i.e., the Fermi energy EF. The CE or localized electron states are modeled by Gaussians where the double half-width 2 σ is related to the mean kinetic energy Ek and is a measure for the binding energy EB of the electron. The dependence between Ek and EB for the 1s electrons of the investigated atoms was determined and the validity of the virial theorem Ek=EB was tested. Such modeling yields an attractive spectroscopic root for analyzing the chemical environment of the positron annihilation site on an atomic level.