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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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4p{*S)6s6p : F0 = 19771, = 1227 4f*(*S)6s5p : Fo = 19834, U = 339 4p(*S)5d6p : F2{dp) = 198) U = 454 Fo = 37575/ = 673
rations, 4p(*S)6s7s, 4f*(*S)6s8s, 4p{*S)6s7p, 4/7(ȣ)6s5/, 4/7(ǣ)5<Z2 and 4/7(8$)6s6d, were also discussed, and the possible influence of configuration interaction was investigated.
Smith and Wybourne [486] found good LS coupling for the 4/* (8$)6s6p configuration consisting of four terms (10P, 8P, eP and 8P') with
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Table 39. Comparison of the observed and calculated positions of the energy levels from the first spectrum of europium (Eu I)
Absorption Spectra of the Europium Ion and Its Complexes 107
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108
Spectroscopic Properties of Europium
12 levels. Here the interaction between the two outer electrons dominates all c&her interact ons. There is also good LS coupling for the 4f*(8S)6s5d configuration consisting of 20 levels arising from four terms (10Z), 8Z>, 6Z) and 8D'). Although the dominating interaction is that between the two outer electrons for this configuration, the interaction between the ^-electrons and the core becomes quite appreciable.
There are 59 levels arising from the terms 10F, *D, *D\ 10Z), ?F, 8F\ 10P, 8P', 6F, 6D and6P (arranged roughly in order of ncreasing energy) of the 4:f7(8S)5d6p configuration. Smith and Wybourne [486] reassigned the position of the 8P' term at ~39400 cm-1. It is also interesting to note the change of £p and values for this configuration which may perhaps be due to a change in sh elding [486].
The spectrum of singly ionized europium (Eu+, EuII). — The seceond spectrum of europium (Eu II) has been measured by Bussell et al. [487]. The ground state is derived from the addition of an electron to the parent core and is found to have the configuration 4/7 (^7/2)63?. They have in particular identified 156 levels originating from to the coupling of a 6«, &p or 5d electron with the 4/7(8$7/2) core. The lowest terms are 9S and 7 S.
Singly ionized europium (Eu+, Eu IT), forms a good example of Jij coupling1. On plotting the observed [487] energy levels (Fig. 19) it becomes immediately clear that we do not have two groups of three levels as originally proposed by Bussell et al. [487] but a group of two and a group of four. Since 8S does not have any quadrupole moment the main interaction is now the interaction between the / and p-electrons. Hence, the upper levels with decreasing order of J will resemble an inverted quartet (Fig. 19) and the lower two levels with increasing J will be a normal doublet.
Wybottrne [488] has recently made a theoretical calculation on Eu+ (Eu II) on a Jij coupling base’s using parameters Q (4/,6p) = 45.15 and
1 The levels of a 4/»6s configuration when arranged on the basis of the L S coupling scheme, give intervals between the successive levels deviating considerably from the Land6 interval rule and so the Russoll-Saunders coupling is not a good approximation in describing the interaction of a 6«-electron with the fn core.
It is customary, in describing such configuration, to use a generalized form of j—j coupling scheme, the JJ coupling. In this schome, the electrons of the core (the states of the core is usually considered on the LS coupl ing basis) are first coupled to form stales characterized by ST Lx Jx. The spin and the angular momentum of the nonequivalent electron are th*=>n coupled to form states characterized by a total angular momentum /. Now, the angular momenta and j are coupled to give total angular momentum J. The energy levels are denoted by JrfJ. In general the levels that occur from the addition of an «-electron to the low-lying fn core in both rare earths and actinides show good coupling except for Sm+(Sm II) where some breakdown of this coupling is noted.
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