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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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1. Cubic: Од, О, Td, Тп, Т
2. Hexagonal: D6h, D6, C6v, Ce, C6fi, D3h, C3h, D3d, D3, C3v, S6, C3
3. Tetragonal: D^, D4, С4V, C^, C*, S4
4. Lower symmetry: D2n, D2, C2v, C2n» C2, Cs, S2, C2
expected for integral J in the case of lower symmetries only. For half-integral values of J all symmetries other than cubic give rise to J + 1/2 levels.
Absorption Spectra of the Europium Ion and Its Complexes 117 Table 44. The number of levels arising from a stale of given J
J Cubic Hexagonal Tetragonal Lower symmetry J Cubic All other symmetries
0 1 1 1 1 1/2 1 1
1 1 2 2 3 3/2 1 2
2 2 3 4 5 5/2 2 3
3 3 5 5 7 7/2 3 4
4 4 6 7 9 9/2 3 5
5 4 7 8 11 11/2 4 6
6 6 9 10 13 13/2 5 7
7 6 10 11 15 15/2 5 8
8 7 11 13 17
The Spectrum of Eu3+ Ion in Crystals
In 1940 Spedding, Moss and Waller [562] investigated several europic salts (EuCl3 ■ 6H2O, EuBr3 • 6H2O, Eu2(SC>4)3 * 8H2O) and pointed out good many vibrationally coupled lines. Later, extensive experimental work [513, 563—567] followed by theoretical investigations [512, 568—572] of the energy levels led to a better understanding of the 119 multiplets of the 4/6 configuration. These multiplets give rise to 295 levels (Table 41). The 119 electrostatic energy levels of the /* configuration have been calculated by Grurer and Conway [571] and an analysis of the Eu3+ absorption spectrum is made by using F2 = 370cm-1 and £4/ = 1360 cm-1. The electrostatic energy matrices for /5 and /6 configurations are reported by Wyrourne [572].
Using the experimental data for Eu3+ in LaCl3 of DeShazer and Dieke [513], Ofelt [512] performed a theoretical calculation using F2 = 401 cm-1 and £4/ = 1320 cm-1 and obtained good agreement between the observed and calculated values for the lowest 10 levels (7Fo,i,2,3,4,5 and 5X)o,1,2,3). The centers of gravity of the Eu3+ energy levels are tabulated in Table 45, and schematically represented in Pig. 22. Although the lines for 5Z)3 and 5Z>4 in the case of Eu3+ doped LaCl3 are identified from the Zeeman effect, Fig. 22 points out that it is rather difficult to assign levels in the 24500—28000 cm-1 region. Above the bIh level, the multiplets of sO and 5L, and 5Z>4 form a rather dense group of levels. The multiplets of 5H are, however, isolated, and these are followed again by a complex group consisting of 5/, 5F and 5K multiplets and also the triplet 3P.
The breakdown of Russell-Saunders coupling is obvious for the 5D multiplets (Fig. 22) and strong admixture with 50 multiplets is expected. The departure from Russell-Saunders coupling is exhibited by the majority of the Eu3+ excited levels.
IVave number xjo"•
118 Spectroscopic Properties of Europium
Table 45. Energy levels of Eu3+ ion
Level Wavenumber (cm-1) Level Wavenun (cm-1)
0 5#3 30483
7Fx 374 *H7 30729
7F2 1036 *H4 30941
7FZ 1888 *H6 30964
2866 31248
7f5 3921 33616
7F' 5022 5A 33870
*D0 17374 *F2 33871
18945 *Fa 33955
21508 5 fx 34085
24456 5F4 34440
*D6 24489 *Po 34457
*l7 25340 6/8 34805
26220 34919
26564 *f5 34932
26600 517 34947
26725 *KS 36179
5«s 26733 *P1 37040
26959 37573
27065 *K7 38809
*L10 27386 39508
5A 27747
J-
Fig. 22. A schematic representation of the Eu3+ energy levels
Absorption Spectra of the Europium Ion and Its Complexes 119
Hellwege et al. [565], however, investigated the polarized spectra of EuCl3 • 6H20, Eu(N03)*6H20 and EufC^HsSO^ * 9HsO crystals in the ultraviolet region and were able to identify a few quintet and 3P2 terms and assign J values to the observed terms. The author [573] has studied the ultraviolet spectrum of EU2O3 by the reflection technique and observed the following groups of closely spaced lines. The occurance of the strong absorption from 34500 cm-1 onwards prevented observations of other Eu3+ absorption lines in the far ultraviolet.
Observed bands in Eu2Oa (in cm-1)
24010 24790 25840 *L10, 27520 SH 31130
24120 *L\ 25000 *L 26040 */(?)] (32820)
25150 *G 26195 I (33390)
1 25340 26400 26560
Crystal field splitting calculations have been carried out by Judd [570] for Eu3+ in an ethylsulphate host. The splittings of the levels were calculated on the basis of the four A% <rn > parameters
A% <r2> = 80, A°<r*> = 63.1, Al <r6> = -38.6 and
Al <r«> = 510 cm-1
taking interactions between levels into account. The agreement between the calculated and observed levels was very good e.g. a discrepancy of ~ 1 cm-1 for the 7F\,2,3, levels.
For the crystal field splitting calculation [513] of Eu3+ in a Lads host the following parameters were used
A% <r2> = 89, A\ <r*> = —38, Al <r6> = — 51 and
Al <r® > = 495 cm-1
The observed multiplets of 7F showed only a deviation of — 2.3 cm-1 from the calculated values. The agreement for the 5D multiplets was not so good due to strong mixing of wavefunctions. The splittings of the 7F multiplets in ethylsulphate and in LaCls hosts are compared in Table 46.
120 Spectroscopic Properties of Europium
Table 46. Observed splittings of the 7F muUiplets of the Eu*+ ion in LaCls and ethylsidphate hosts
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