Lanthanide elements spectroscopic properties

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. 

Magnetic and spectroscopic properties of free atoms depend on the interplay of the interactions Hi and H2, since they determine the magnetic moment and the energy spectrum of the atom. Models of this interplay (coupling models) are assumed for lanthanide and d-transition elements. We shall examine in a simple way possible couplings, and point out the difficult case of actinide atoms. 

To provide an overview of the rare-earth compounds which have been studied under pressure so far, table 1 lists the compounds, with respect to the doped ion and with the respective references. Obviously, Eu has been studied under pressure in much more host matrices than any of the other elements. This situation is similar to the observations made by Gorller-Walrand and Binnemans (1996), who reviewed the experimental data on spectroscopic properties of trivalent lanthanide ions doped into crystalline host matrices at ambient pressure. They found that Nd and Eu alone built up around 50% of all studies. 

The decrease in radius in moving from La3+ to Lu3+ is 117.2 to 100.1 pm which is less than 114-88 pm for elements Ca2+ to Zn2+. In the case of Sc3+ to Ga3+, the radius decreases from 88.5 to 76 pm. This comparison shows that the percent contraction is greater in the case of Sc3+ to Ga3+ and Ca2+ to Zn2+ series than lanthanides series. The fact is that the magnitude of the lanthanide contraction is small and the usual interpretation of magnetic and spectroscopic properties of the lanthanides are inconsistent with the idea of considerable shielding of 4/ electrons from the chemical environment of the ion by the 5s25p6 configuration. Thus the implication that the size of lanthanide atoms or ions is determined by the 4 fn subshell must be incorrect. 

In their magnetic and spectroscopic properties the lanthanides show important differences from the d-block elements. This happens because the 4/ electrons are pretty well (although not totally) shielded from external fields by the overlying 5s2 and 5p6 shells. The states arising from the various 4/" configurations therefore tend to remain nearly invariant for a given ion. 

In this review of multistep laser photoionization of the lanthanides and actinides, we hope that we have introduced the reader to a number of laser techniques for determining spectroscopic properties of these elements. We have undoubtedly overlooked some techniques and some papers on the subjects we did cover. The importance of laser methods in studying the spectroscopy of the lanthanides and actinides is well established and future applications should greatly expand our knowledge of these elements. 

Spectroscopic Properties of the f-Elements in Compounds and Solutions, W.T. CamaU, J.V. Beitz, H. Crosswhite, K. Rajnak, and J.B. Mann. In Systematics and the Properties of the Lanthanides, S.P. Sinha (Ed.), D. Reidel Publishing Company, Boston, chapter 9,... 

Experimental investigations of spectroscopic and other physical-chemical properties of actinides are severely hampered by their radioactive decay and radiation which lead to chemical modifications of the systems under study. The diversity of properties of lanthanide and actinide compounds is unique due to the multitude of their valency forms (which can vary over a wide range) and because of the particular importance of relativistic effects. They are, therefore, of great interest, both for fundamental research and for the development of new technologies and materials. The most important practical problems involve storage and processing of radioactive waste and nuclear fuel, as well as pollution of the environment by radioactive waste, where most of the decayed elements are actinides. 

Although considered as inessential elements for life, the lanthanides are certainly biologically active and have numerous applications of importance in biological analysis and in both diagnosis and therapy in medicine. These applications exploit not only the spectroscopic and magnetic properties of various naturally occurring lanthanides but also the activity of synthetic radioisotopes. This chapter is focused on recent developments in such areas and on the basic aspects of coordination chemistry, which underlie die use of lanthanide(III) species in particular. 

In chapter 114, O. Vogt and K. Mattenberger examine the magnetic behaviors of the lanthanide and actinide Bl, NaCl-type structures. The magnetic properties of a sample depend upon the spectroscopic state of the f-element and the possibility of J-mixing, the electric crystalline field, the exchange interactions and hybridization. The competition between these various factors can make the materials complicated or simple with respect to their magnetic behaviors. 

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