Atomic terbium

Terbium is reasonably stable in air. It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. Two crystal modifications exist, with a transformation temperature of 1289oC. Twenty one isotopes with atomic masses ranging from 145 to 165 are recognized. The oxide is a chocolate or dark maroon color. 

On the other hand, lanthanides with 100% isotopical purity such as terbium or holmium are preferred to simplify the operation and minimize decoherence in spin qubits. In this respect, the existence, for some lanthanides, of a manifold of electronuclear states can provide additional resources for the implementation of multiple qubit states within the same molecule [31]. All atoms in the first coordination sphere should be oxygen, and the sample should be deuter-ated if the compound contains hydrogen, to avoid interaction with other nuclei spins. Again, POM chemistry has been shown to provide ideal examples of this kind. 

Dysprosium - the atomic number is 66 and the chemical symbol is Dy. The name derives from the Greek dysprositos for hard to get at , due to the difficulty in separating this rare earth element from a holmium mineral in which it was found. Discovery was first claimed by the Swiss chemist Marc Delafontaine in the mineral samarskite in 1878 and he called it philippia. Philippia was subsequently found to be a mixture of terbium and erbium. Dysprosium was later discovered in a holmium sample by the French chemist Paul-Emile Lecoq de Boisbaudron in 1886, who was then credited with the discovery. It was first isolated by the French chemist George Urbain in 1906. 

Terbium - the atomic number is 65 and the chemical symbol is Tb. The name derives from the village of Ytterby in Sweden, where the mineral ytterbite (the source of terbium) was first found. It was discovered by the Swedish surgeon and chemist Carl-Gustav Mosander in 1843 in an yttrium salt, which he resolved into three elements. He called one yttrium, a rose colored salt he called terbium and a deep yellow peroxide he called erbium. The chemist Berlin detected only two earths in yttrium, i.e., yttrium and the rose colored oxide he called erbium. In 1862, the Swiss chemist Marc Delafontaine reexamined yttrium and found the yellow peroxide. Since the name erbium had now been assigned to the rose colored oxide, he initially called the element mosandrum (after Mosander) but he later reintroduced the name terbium for the yellow peroxide. Thus the original names given to erbium and terbium samples are now switched. Since Bunsen spectroscopically examined Mosander s erbium (now terbium) sample and declared that it was a mixture, the question of who actually discovered terbium, Mosander or Delafontaine remains unresolved to this day. 

Terbium may be identified by various instrumental techniques including atomic absorption and emission spectrophotometry and neutron activation analysis. 

It was noted earlier that the charge density of a narrow resonance band lies within the atoms rather than in the interstitial regions of the crystal in contrast to the main conduction electron density. In this sense it is sometimes said to be localized. However, the charge density from each state in the band is divided among many atoms and it is only when all states up to the Fermi level have contributed that the correct average number of electrons per atom is produced. In a rare earth such as terbium the 8 4f electrons are essentially in atomic 4f states and the number of 4f electrons per atom is fixed without reference to the Fermi level. In this case the f-states are also said to be locaUzed but in a very different sense. Unfortunately the two senses are often confused in literature on the actinides and, in order not to do so here, we shall refer to resonant states and Mott-localized states specifically. 

Due to the presence of hard anionic oxygen atoms, phenolate and carboxylate groups are often employed as donors in lanthanide coordination chemistry. Ligand [L18]4- is reported as an excellent triplet sensitizer for lanthanide luminescence (61). Indeed aqueous lifetimes of 0.57 and 1.61 ms are reported for europium and terbium, respectively quantum yields of 0.20 and 0.95 respectively refer to the efficiency of the energy transfer process alone. 

It is interesting to note that the emission spectra of the terbium chlorides solvated with H20 and D20 show no discernible differences. Since the rare-earth chlorides solvated with D20 are isostructural with the chlorides solvated with H20 and since the emission spectra are essentially identical, Freeman et al believe that the variations in lifetime are not brought about by changes in the radiative-transition probabilities, but are a consequence only of changes in radiationless quenching efficiencies. They speculate that the decreased efficiency upon substitution of D20 for H20 must be related to the large changes in vibrational frequencies associated with substitution of the H atoms by the D atoms. 

Kleinerman and co-workers (158) reported an enhancement of fluorescent yield of chelated lanthanide ions by Lewis bases. They observed that in liquid, plastic, and glassy solutions containing terbium europium, and samarium chelates, the use of Lewis bases accomplishes the same effect as substituting deuterium for hydrogen. Not all bases, however, are equally effective. The molecular size of the base does not appear to be particularly important, since strong enhancement effects can be obtained with both bulky and small molecules. The nature of the atom of the base having the unshared electron pair is not a determining factor in the enhancement phenomenon. 

Atomic number Symbol Element 21 Sc Scandium 39 Y Yttrium 57 La Lanthanum 58 Cfc Cerium 59 Pi Praseodymium 60 Nd Neodymium 61 Pm Promethium 62 Sm Samarium 63 Eu Europium 64 Gd Gadolinium 65 Tb Terbium 66 Dy Dysprosium 67 Ho Ilolmium 68 Er Erbium 69 Tm Thulmm 70 Yb Ytterbium 71 Lu Lutetium... 

It is well-known that concentration quenching of the 5D4 luminescence is not observed in usual glasses whose rare-earth concentration is limited to a few atomic percent. In some sodium fluorophosphate glasses, whose terbium concentration is as high as 35 atm%, 5D4 luminescence quenching is found to occur at concentration of 20 atm% (3.3 1021 ions cm-3) and greater [145]. 

Lanthanide elements (referred to as Ln) have atomic numbers that range from 57 to 71. They are lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). With the inclusion of scandium (Sc) and yttrium (Y), which are in the same subgroup, this total of 17 elements are referred to as the rare earth elements (RE). They are similar in some aspects but very different in many others. Based on the electronic configuration of the rare earth elements, in this chapter we will discuss the lanthanide contraction phenomenon and the consequential effects on the chemical and physical properties of these elements. The coordination chemistry of lanthanide complexes containing small inorganic ligands is also briefly introduced here [1-5]. 

Structure Non-hydrated rare earth fluorides have two different crystal systems, a hexagonal system (lanthanum to terbium) and an orthorhombic system (dysprosium to lutetium, yttrium). In the crystal of LaFs, the central ion is nine coordinated by nine fluoride atoms. Each fluoride atom further connects with two lanthanum atoms through a [13-bridge to form an infinite polymer. 

Figure 2.43 (a) [Lns] clusters, hydrogen atoms have been removed for clarity (b) view of the cluster where ligands have been removed for clarity [77]. (Reproduced from S. Petit, F. Baril-Robert, G. Pilet, C. Reber and D. Luneau, Luminescence spectroscopy of europium(III) and terbium(III) penta-, octa-and nonanuclear clusters with fS-diketonate ligands, Dalton Transactions, 34, 6809-6815, 2009, by permission of the Royal Society of Chemistry.)... 

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