Investigation of soft x-ray processes contributing to chemical shift in 3d transition metals

Full text: Soft x-ray analysis is being evaluated as a method for determining the concentrations of different valence states in an industrial based materials. It has been shown that different valence states of elements such as Fe, Mn and Ti can be identified from the shift and relative intensities of the long wavelength L-alpha and L-beta emission lines (i.e. 15 to 30 Angstroms). This is commonly called the 'Chemical Effect'. Many problems are associated with the implementation of this effect for routine quantitative analysis. These include self-absorption, the reproduceability of the sample preparation, and the limited resolution of conventional XRF equipment. In this project we are investigating the feasibility of using the chemical effect to determine the Fe2+/Fe3+ ratio in a range of well defined materials and to compare the results obtained with other methods such as X-ray diffraction and direct chemical analysis. In conjunction with this, we are also investigating,(a) the influence of self absorption and the distortion it can introduce into the spectral pattern, and (b) how to deconvolute the instrumental function from an observed spectrum to obtain the pure L emission spectrum. Work is in progress on the self absorption component, by investigating the emission from a range thin Fe films of known thicknesses. The instrumental aberration function is being determined from the shape 9th order Fe K alpha emission line which coincides with the Fe L emission lines. As the shape of the pure Fe K alpha emission profile can be determined by other means, it should be possible to deconvolute this from the 9th order spectrum and obtain the residual instrument function. Copyright (1999) Australian X-ray Analytical Association Inc