Soft X-ray spectroscopy

X-ray spectrometry at low energies (< 1000 eV), long wavelengths (>12 Å) presents special problems due to the inefficiency with which such X-rays are generated, the ease with which they are absorbed, and the difficulty of finding suitable dispersing elements. Advantage can, however, be taken of the ready absorption of these “soft" X-rays since their escape depth from most materials rarely exceeds one micron. Soft X-ray spectroscopy is therefore nanometer spectroscopy. Furthermore soft X-rays show large “chemical effects" which can be used to infer the chemical state of the emitting atom. The special problems associated with the production and dispersion of soft X-rays are considered in this paper together with methods for calculating the depth of X-ray production from surface layers. Examples are also given of the changes in peak shape, position and profile which can be used to assess the valency and ligand environment of the emitting atom.