ANOMALOUS X-RAY-ABSORPTION OF THE MOC LINES IN THE RARE-EARTH ELEMENTS

The presence of an unfilled inner electron shell in the rare earth ele ments is manifested in x-ray absorption effects that are unique to the energy region including the Malpha and Mbeta lines of these elements. In contrast to the normal edge-type absorption, this anomalous absorp tion appears as an absorption line. A method is presented here for the quantitative determination of the extent of this anomalous absorption . Solid hulk metal samples, excited with a monoenergetic electron beam , were examined with a wavelength-dispersive x-ray spectrometer. The d iscussed method makes the experimentally determined absorption indepen dent of both the detection efficiency and atomic data such as the fluo rescence yield and transition probabilities. A simple empirical model is proposed to explain the dependence of the absorption of the Malpha line on the absorption path length, which was varied by the primary be am energy. Normal and anomalous absorption are treated as independent and competing processes in this model. Atomic data such as the mass ab sorption coefficients pertinent to the anomalous absorption of the Mal pha lines were also determined and are presented.