Ytterbium ionization energy

Fig. 5. Experimental XPS data (Lang et al. 1981) for the position of the 4f level relative to the Fermi energy. For cerium the data point by Platau and Karlsson (1978) is used. These experimental data are denoted by open squares. The filled circles are the calculated values for AEimy (Johansson 1979) (including the zl(n) correction). For ytterbium the dotted square is used to show that this is not an experimental value but is derived from its fourth ionization energy, as described in section 8.

The rare earth (RE) ions most commonly used for applications as phosphors, lasers, and amplifiers are the so-called lanthanide ions. Lanthanide ions are formed by ionization of a nnmber of atoms located in periodic table after lanthanum from the cerium atom (atomic number 58), which has an onter electronic configuration 5s 5p 5d 4f 6s, to the ytterbium atom (atomic number 70), with an outer electronic configuration 5s 5p 4f " 6s. These atoms are nsnally incorporated in crystals as divalent or trivalent cations. In trivalent ions 5d, 6s, and some 4f electrons are removed and so (RE) + ions deal with transitions between electronic energy sublevels of the 4f" electroiuc configuration. Divalent lanthanide ions contain one more f electron (for instance, the Eu + ion has the same electronic configuration as the Gd + ion, the next element in the periodic table) but, at variance with trivalent ions, they tand use to show f d interconfigurational optical transitions. This aspect leads to quite different spectroscopic properties between divalent and trivalent ions, and so we will discuss them separately. 

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