13 - Soft x-ray fluorescence spectroscopy

Abstract

This chapter describes the characteristic features of soft x-ray fluorescence (SXF) spectroscopy, specialized spectrometers, and detectors that have been developed for measuring the very weak spectra and some typical experimental results. X-ray fluorescence spectra are produced when x-rays are used to excite the characteristic x-ray emission spectra of a particular element. Very low yields for radiative transitions in the soft x-ray spectral range made SXF impractical before the advent of powerful synchrotron sources. Consequently, the history of SXF spectroscopy is provided by the measurement of soft x-ray emission (SXE) spectra excited by energetic electrons. The soft x-ray spectroscopy, which has been discussed in this chapter, and hard x-ray spectroscopy have developed along largely independent paths. Soft x-rays are strongly absorbed, requiring windowless operation from the source to sample to spectrometer and detector, and the use of reflective optics. Normal incidence reflectance is very low, requiring the use of grazing incidence optics, and the accommodation or correction of the large aberrations that this implies.