Trivalent ions, energy levels

The field of lathanide lasers is mature but not exhausted. Additional laser schemes and materials will undoubtedly be exploited. There are 1639 free-ion energy levels associated with the 4fn electronic configurations of the thirteen trivalent lanthanides. Yet, of the 192,177 possible transitions between pairs of levels, by mid-1979 only 41 had been used for lasers. It is certain that given suitable pump sources and materials, stimulated emission involving many... 

Excitation of these ions using 40,000 cm i energy results in various excited states for each ion. Each state relaxes by phonon processes until the terminal excited state is reached, from which emission of a visible photon results. But we need to remember that any time we put a trivalent rare earth ion into a host crystal to form a phosphor, we will modify its free-ion energy levels, depending upon the site symmetry and crystal field strength. 

Fig. 1.5 Dieke s diagram free-ion energy levels of trivalent rare earth ions. Reproduced from Ref. [22] by permission of John Wiley Sons Ltd...

In what follows we briefly review some of the previous attempts to analyze the available spectra of plutonium (6). In addition, we estimate energy level parameters that identify at least the gross features characteristic of the spectra of plutonium in various valence states in the lower energy range where in most cases, several isolated absorption bands can be discerned. The method used was based on our interpretation of trivalent actinide and lanthanide spectra, and the generalized model referred to earlier in the discussion of free-ion spectra. 

In the ionic implantation, a beam of trivalent ions (e.g. B+ ions), is used to produce a p+ layer. Pentavalent ions (e.g. P ions), instead, create an n+ layer. The main advantage of this technique rely in the fact that the ions penetrate the crystal only for a short distance from the surface ( 200nm). The penetration depth depends on the beam energy (25 100keV). Typical doping level is 1018 1019ions/cm3. With such a high dopant concentration, the layer becomes practically a metal. 

Weak crystalline field //cf //so, Hq. In this case, the energy levels of the free ion A are only slightly perturbed (shifted and split) by the crystalline field. The free ion wavefunctions are then used as basis functions to apply perturbation theory, //cf being the perturbation Hamiltonian over the / states (where S and L are the spin and orbital angular momenta and. 1 = L + S). This approach is generally applied to describe the energy levels of trivalent rare earth ions, since for these ions the 4f valence electrons are screened by the outer 5s 5p electrons. These electrons partially shield the crystalline field created by the B ions (see Section 6.2). 

Figure 6.1 An energy-level diagram for trivalent lanthanide rare earth ions in lanthanum chloride (after Dieke, 1968).

Two specific features determine the similarity and difference of energy levels in di- and trivalent ions of rare-earth elements. First, isoelectronic configurations of TR " and of the next elements in the periodic system determines a qualitatively similar pattern of terms and multiplet levels, namely for TR the order of the 4/ -configuration levels and of excited 4f 5d-configuration levels... 

Carnall, W. T. Fields, P. R. Rajnak, K. Electronic energy levels of the trivalent lanthanide aquo ions. I-IV. J. Chem. Phys. 1968, 49(10), 4424-4455. 

Figure 2.7 Energy levels of trivalent rare earth ions. (A.P.B. Sinha— Fluorescence and Laser Action in Rare Earth Chelates in Spectroscopy in Inorganic Chemistry Ed. CNR Rao and JR Ferraro.)...

Fig. 6. Complete 4f (left) and 4f 15d (right) energy level diagram for all trivalent RE ions.

Fig. 10. Complete 4f and 4f" 5d energy level diagram for all trivalent RE ions in YLF obtained by the first-principles relativistic Cl calculations. For each element, the compositions of the 41" configurations are shown on the left and those of 41 5d configurations are shown on the right, respectively. See text for further explanations.

Electronic Energy Levels of the Trivalent Lanthanide Aquo Ions. II. Gd3+, W.T. Camall, P.R. Fields, andK. Rajnak. J. Chem. Phys. 49, 4443-4446 (1968). 

Electronic Energy Level and Intensity Correlations in the Spectra of the Trivalent Actinide Aquo Ions. III. Bk3+, W.T. Camall, J.V Beitz, and H. Crosswhite, J. Chem. Phys. 80, 2301-2308 (1984). 

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