The m alpha,beta x-ray emission spectra of the heavy rare earths.

The m alpha,beta x-ray emission spectra of some of the heavy rare earths were measured using a high resolution x-ray spectrometer. The x-ray spectrometer was designed to allow the preparation of pure samples in ultra-high vacuum conditions so that accurate spectra could be measured. Due to the large number of measurements necessary, the spectrometer was automatically controlled by a microprocessor based system. From the high resolution data obtained, it has been possible to produce an explanation of the gross structures seen in the rare earth m alpha,beta x-ray emission spectra. It has been shown that the spectra are made up from several competing processes but that the main features can be explained in terms of resonant excitation of a 3d electron to the 4f shell followed by 4f - 3d emission and by normal 4f - 3d emission after ionisation of a 3d electron. Modifications to the spectra caused by excited final state transitions have also been observed. The dramatic effects on the malpha spectra of ytterbium due to chemical combination have also been explained in terms of the reduction of the 4f occupancy from 4f14 to 4f13. It has been shown that much of the published data for the m alpha,beta rare earth emission spectra is incorrect. The distorting effects of self absorption and sample contamination have been shown to be particularly severe for the rare earths.