Self-Absorption Effects in the Soft X-Ray Ma and M{J Emission Spectra of the Rare Earth Elements

The M a and M ~ emission spectra and the M IV and M v absorption spectra have been stud~ed for th~ r~re earth elements. It is conclusively shown that the complicated multiplet structure o~served .1I~ the enusslOn spectra is not real emission structure but is, inst~ad, pro?u~ed b! sample self-absorption. This Is.demonstrated by observing the emission spectra over wIde vanatlOns In take-?ff. angle and bo~bardlng-electron energies and finally by comparing the detailed structure of both the emISSIOn and absorptIOn spectra. The M and M absorption structure completely overlaps the M a and M p emission lines which are e:u:h found to I~ave butVone intensity maximum when obtained under conditions of minimu~ se~f-abs0IJ>hon. Some of these spectra have never been shown previously, while other;; have been studIe~ In detaIl by several investigators. Points of agreement and disagreement with preVIOUS work are ~entlOne? and the wavelengths of the emission lines and absorption edges are listed for all of the lantharndes. It IS concluded that 4f-->3d electron transitions are reversible in these elements. .