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Europium - Sinha S.P.

Sinha S.P. Europium - Springer-Verlag, 1967. - 88 p.
Download (direct link): europium1967.djvu
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Eu (Benzoylacetone) 8
Solid 99 560 535 [640]
EtOH—MeOH soln. 99 545 - [640]
EtOH—MeOH soln. 99 - 160 [642]
Eu(DBM),
Solid 99 369 80 [642]
EPA solution 99 360 - [642]
EtOH—MeOH soln. 91 - 70 L646]
Eu(DBM)4
Solid 99 533 533 [642]
EPA soln. 99 451 — [642]
134 Absorption Spectra of the Europium Ion and Its Complexes
Table 50 (continued)
Complexes Transition t in jxsec References
77° K 300° K
EtOH—MeOH soin. - 65 [646]
Methylcyclohexane soin. 99 - 142 [646]
Eu(DBM)x 99 500» — [539]
Eu(TTA)31H20
EPA soin. 99 — 336 [654]
EtOH—MeOH soin. 99 — 335 [654]
DMF soin. 99 — 519 [654]
Acetone soin. 99 — 389 [654]
Eu(TTA)3-TTA
EPA soin. 99 — 435 [654]
EtOH—MeOH soin. 99 — 350 [654]
DMF soin. 99 — 500 [654]
Acetone soin. 99 — 550 [654]
Eu(TTA)3 [646]
EtOH—MeOH soin. 99 — 371
Eu(HFA)3 [644]
EtOH—MeOH 99 — 430
Eu(HFA)3 • 2HaO
EPA soin. 99 — 470 [654]
EtOH—MeOH soin. 99 ■— 490 [654]
DMF soin. 99 — 775 [654]
Acetone Soin. 99 — 554 [654]
Eu(PFHD)3 [648]
EtOH—MeOH soin. 99 — 438
Eu(Dip)2Cl3-H20(CH30H soin.) 99 — 250 [645]
Eu(Terp)2Cl3 • H20(CH30H soin.) 99 — 310 [645]
a The analysis of this compound is not available, and possibly a piperidine adduct.
DBM = dibenzoylmethide,
TTA = thenoyltrifluoroacetylacetonate HFA = hexafluoroacetylacetonate,
Dip = 2,2'-dipyridyl,
Terp = 2,2/,2"-terpyridyl
Chapter 7
Possible Uses and Applications of Europium
For a long time the rare earth elements did not find extensive application except for “Welsbach mantles” possibly because of their scarcity. However, the significant break-through over the separation problems for these elements by the ion exchange technique really added “muscles” to the lean and hungry industry of the past, and, in fact, many people hold somewhat overoptimistic attitudes towards their future. Although various fancy uses of rare earths are glamourizing the scientific and non-scientitic literature, American Potash, one of the biggest concerns in the rare earth industry, still feels that their use “in such fields as arc carbons, glass polishing, catalysts and mischmetal for flints and alloys ... is and will remain the bread and butter of the industry”. There is, however, no doubt that these elements possess unique properties which can be exploited for newer uses and research may pay off well in the end. In the following pages a few selective uses of europium are described.
As a Possible Laser Material
The narrow linewidth of the intra /—/ transitions and the weak crystal field interactions have made the rare earths (and the actinides) very attractive candidates for laser research. The applications of laser are varied. In particular, laser beams produce highly coherent and monochromatic light, and have proved to be very useful for interference and diffraction experiments. It is possible to use laser light for the controlled excitation of materials keeping their bulk unaffected. In the field of communications and ranging, the narrow laser beam has advantages over other information carrying systems, especially for point to point communication in space, where atmospheric attenuation does not interfere with the propagation of radiation. There are a few books on laser and the reader may consult any of these for a theoretical aspect of the subject. The author, however, found the book by Birnbatjm \655\ quite handy for reference.
Stimulated emission of Eu3+ has been observed for the 5D0 -► 7F2 band in doped crystals and in chelate complexes. In the case of Eu3+
136
Possible Uses and Applications of Europium
doped Y2O3 this emission occurs [622] at 6113 A at 223° K. Eu3+ doped Gd2C>3 may also be suitable as laser material.
Ftlipesctt et al. [656], and Schmitschek and Schwarz [657] in 1962 were the first to point out the possibility of using the rare earth complexes as laser materials due to the low pump power necessary to excite these complexes via the IMET process and the relatively high quantum yield. The diminished lattice coupling of the rare earth ions in complexes may be very important in the liquid laser where quenching is quite serious.
The first reported laser action in rare earth complexes was obtained by Lempicki and Samelson [658] for europium benzoylacetonate in alcoholic solution. The laser parameters for this complex have also been evaluated by Lempicki and coworkers [659, 660] who found a slightly better quantum efficiency (0.8) for europium benzoylacetonate than for ruby (0.7), the solid state laser. The laser action of europium benzoylacetonate has also been investigated by Schimitschek [661] and Bhattmik et al. [662]. Some other complexes of Eu3+ viz. dibenzoylmethide [663, 664], Jm-4,4,4-trifluoro-l(2-thienyl)-l,3-butanedione [665], thenoyl-trifluoroacetonate [666, 667] were also found to lase.
The intense absorption band in many complexes often presents problems, and it becomes difficult to excite effectively a large volume of the sample without loosing a large portion of the pump energy. However, a proper choice of ligand with good coordinating power may partly solve this problem. It has been found that the triplet state of the organic ligand may act as an “electron sink” and cannot be compensated for. An interesting phenomenon was observed [668] in the case of europium trifluoroacetylacetonate. If the complex is prepared in a piperidine medium, the intensity of the 5Do -*■ transition is very low and no laser action can be observed from this complexes. However, the complexes prepared using ammonia in place of piperidine show laser action. It is probable that energy degradation takes place via the manyfold energy levels of the ligand, and the author believes that the most probable explanation is the reabsorption of the intramolecularly transferred energy to a higher level originating from the ligand.
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