Atomic ytterbium

The previous experiments on ytterbium [50] have been extended using resonance ionization spectroscopy on a fast atomic ytterbium beam [71]. 

The ultra-stable atomic clock of the US National Institute of Standards and Technology (NIST) with an instability of 10 , utilizes spin-polarized, ultra-cold atomic ytterbium (Hinkley et al. 2013). 

According to this assignment the differentiating electron, that is, the final electron to enter the atom of lutetium, wss seen as an f electron. This suggested that lutetium should be the final element in the first row of the rare earth elements, in which f electrons are progressively filled, and not a transition element as had been believed by the chemists. As a result of more recent spectroscopic experiments the configuration of ytterbium has been altered to (27)... 

An interesting effect of the half-filled and filled 4/ shell is shown when a graph is made of the melting point of the elements. Such a graph is shown in Figure 11.6. Although it is not shown, a plot of atomic radii for the metals shows a large increase in size for Eu and Yb. For example, the radii of Sm and Gd are approximately 180 pm, but Eu, situated between them, has a radius of 204 pm. The difference in size between Yb and the atoms before and after it also amounts to about 20 pm. Europium and ytterbium... 

Within the lanthanides the first ones from La to Eu are the so-called light lanthanides, the other are the heavy ones. Together with the heavy lanthanides it may be useful to consider also yttrium the atomic dimensions of this element and some general characteristics of its alloying behaviour are indeed very similar to those of typical heavy lanthanides, such as Dy or Ho. An important subdivision within the lanthanides, or more generally within the rare earth metals, is that between the divalent ones (europium and ytterbium which have been described together with other divalent metals in 5.4) and the trivalent ones (all the others, scandium and yttrium included). 

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. 

Scandium - the atomic number is 21 and the chemical symbol is Sc. The name derives from the Latin scandia for Scandinavia , where the mineral were found. It was discovered by the Swedish chemist Lars-Fredrik Nilson in 1879 from an ytterbium sample. In the same year, the Swedish chemist Per Theodore Cleve proved that scandium was Mendeleev s hypothetical element eka-boron , whose properties and position in the Period Table Mendeleev had previously predicted. 

For the subject matter of this book, it is of particular interest to consider the situation for a non-crystalline system analogous to that of crystalline ytterbium or strontium under pressure, namely that when a valence and conduction band are separate or overlap slightly. If the degree of overlap can be changed by varying the mean distance between atoms, the composition or the coordination number then a metal-insulator transition can occur. Many examples will be discussed in this book, particularly amorphous films of composition (Mgi- )j(By3, liquid mercury at low densities, and liquid tellurium alloys in which the coordination number changes with temperature. The transition is, we believe, of Anderson type. 

The value of the Weiss constant 0 was 43 1°K and suggested that Eu2RuH6 becomes ferromagnetic at some temperature below 77°K. The magnetic susceptibility for Yt RuHe appeared to be consistent with di-valent ytterbium, which theoretically has zero atomic moment. The small paramagnetism observed experimentally was assigned to Yb23 impurity. 

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