Extended x‐ray emission fine structure and high‐energy satellite lines state measured by electron probe microanalysis

Abstract

AbstractThe Kα satellite or shake‐off lines can be observed by wavelength‐dispersive spectrometry on the high‐energy side of the main Kα peak. Occasionally, chemical state analysis of an emitting atom has been attempted using the shape and position of these lines. Recent extensive theory and experiment have shown that it is fruitful to take a similar approach using extended x‐ray emission fine structure (EXEFS) arising from the radiative Auger effect (RAE). This fine structure is found in a low‐intensity spectrum on the low‐energy side of the Kα peak.We have studied the RAE spectra of the Kα lines of the elements F through to Ca by EPMA. The RAE peaks have energies close to the KLL energies of Auger transitions. In the lighter elements in this series, it was found that the difference between Kα and the RAE peak energies becomes quite small. For elements lighter than fluorine, it is difficult to observe the RAE peaks because they are overlapped by the main Kα line. At the higher energy end of the series, the intensity of the RAE lines becomes very small. The utility of the RAE lines for state analysis is limited, in practice, to the elements F through to Ca. The extended x‐ray emission fine structure (EXEFS) of the RAE spectra has been used to calculate local bonding parameters.Both shake‐off and RAE spectra associated with the F Kα line have been studied experimentally in the rare earth fluorides. The KLL RAE moves to lower energy as the atomic number of the rare earth cation increases. This has been confirmed theoretically by calculating electron energies using discrete variational Xα molecular orbital theory. The shake‐off peaks increase in intensity relative to the main Kα peak because atomic number increases, contrary to expectation. It is considered that this could be due to temporary covalency. The EXEFS of the RAE spectra has been used to calculate local bonding parameters. Copyright © 2001 John Wiley & Sons, Ltd.