Thulium spectroscopy

The behaviour of lanthanum in dimethyl formamide (DMF) is quite different from that in methanol and acetonitrile. While perchlorate forms inner sphere complexes with lanthanides in acetonitrile [31], no such complexes are formed in DMF [32]. The coordination properties in DMF solutions were studied by NMR and UV-Vis spectroscopy techniques [33,34], The rate of DMF exchange in the system ytterbium perchlorate-DMF-CD2CI2 was slow enough that 1H NMR resonances permitted the determination of the mean coordination number to be 7.8 0.2. Similar determination in the case of thulium(III) gave a mean coordination number of 7.7 0.2. Thus it was concluded that the predominant species in heavy lanthanides is Ln(DMF)g+ in DMF solutions. In the case of lighter lanthanides, the following equilibrium exists... 

A. Stark et al.. Intercavity Absorption Spectroscopy with Thulium-doped Fibre Laser. Opt. Commun. 215, 113 (2003)... 

Fig. 1. Energy levels of trivaient lanthanides below 43000 cm (5.3 eV) arranged according to the number q of 4f electrons. Excited levels known frequently to luminesce are indicated by a black triangle. The excited levels corresponding to hypersensitive transitions from the ground state are marked with a square. For each lanthanide, J is given to the right (in the notation of atomic spectroscopy, ] is added to the Russell-Saunders terms as lower-right subscripts). When the quantum numbers S and L are reasonably well-defined, the terms are indicated to the left. It may be noted that the assignments and F< in thulium(lll) previously were inverted these two levels with 7 = 4 actually have above 60% of H and F character, respectively. Calculated 7-levels are shown as dotted lines. They are taken from Carnall et al. (1968) who also contributed decisively to the identification of numerous observed levels, mainly by using the Judd-Ofelt parametrization of band intensities.

Cleve in Sweden concentrated on the erbium that remained after the separation of ytterbium. He carried out extensive separation work in 1878-9 and obtained three fractions. Using spectroscopy he found that one was erbium but the other two contained new elements. He called these thulium, after Thulia, the old Roman name of the uttermost North, and holmium, after Holmia, the Latin name of Stockholm. As already mentioned, Delafontaine and Soret had in fact found lines of a foreign element during the spectral analysis of an erbium sample they had obtained from Marignac. This element, erbium-X or element-X, appeared to be identical with holmium. In tables of discoverers, Delafontaine and Soret are mentioned alongside Cleve. 

The temperature dependence of the quadrupole splitting of Tm in TmES yielded an estimate of the values of the CEF parameters for the Tm ion in the ethylsulfate structure. Since optical absorption spectroscopy had previously furnished estimates of the four parameters needed to characterize the CEF in this structure [Wong and Richman (1961)], their determination in this case provided a valuable cross-check on the validity of the method which has been outlined in section 2.1.3. The experiments also revealed a substantial shielding of the 4f electrons from the crystal field, as has been described for the case of thulium metal in section 2.1.3. 

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