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Electronic Energy Levels in the Trivalent Lanthanide Aquo Ions. I.
Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+
W. T. Carnall, P. R. Fields, and K. Rajnak
Citation: J. Chem. Phys. 49, 4424 (1968); doi: 10.1063/1.1669893
View online: http://dx.doi.org/10.1063/1.1669893
View Table of Contents: http://jcp.aip.org/resource/1/JCPSA6/v49/i10
Published by the American Institute of Physics.Additional information on J. Chem. Phys.
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V OLUME 4 9, N UMBER 1 0

1 5 N OVEMBER 1 968

Electronic Energy Levels i n t he Trivalent Lanthanide Aquo Ions.
I P rH, N d H, P mH, S m H , D yH, HOH, E r3+, a nd T m3 +*


W. T.


P. R.




Chemistry Division, Argonne National Laboratory, Argonne, I ninois
(Received 2 April 1968)
The free-ion energy-level schemes of t he PtJ+, N d3+, P m3+, S m3+, Dya+, Hoa+, EtJ+, a nd Tm3+ a quo ions
have been determined from their absorption spectra i n d ilute acid solution a t 25°. Energy-level assignments
were m ade b y comparison w ith c rystal spectra, a nd o n t he basis of correlations between calculated a nd
observed b and intensities. F or m ost of t he ions, i t was possibleto identify several transitions giving rise
t o b ands a t energies as high as 45 000-50 000 c m-1 • Sufficient numbers of assignments were m ade t o j ustify
inclusion of t he effects of configuration interaction i n t he calculation of the energy-level parameters. Variation of t he electrostatic, s pin-orbit coupling, a nd configuration-interaction parameters across t he l anthanide
seriesis examined.

I n 1907, BecquereP first showed t hat the absorption
bands of crystalline lanthanide compounds could be
resolved into sharp lines a t low temperatures. He further reported t hat m any of these lines exhibit a Zeeman
effect. By 1929, Bethe2 had developed the theory for
term splitting which results from the influence of a
crystalline electric field of a given symmetry on anatom, b ut the gross term structure and the nature of
the sharp lanthanide absorption lines were not understood. Thus, while there was considerable interest manifest in the spectroscopic properties of the lanthanides
in the early thirties,8 the interpretation was very limited.
Experimentally, i t was extremely difficult to prepare
high-purity lanthanide compounds prior to the development of theion-exchange processes used today. Prandt14
referred to his work with the rare earths over a period
of 20 years, which finally led to the preparation of relatively pure compounds of most of the members of t he
4fN series. These were used in 1934 to obtain the first
complete (except for Pm8+) set of lanthani~e-solution
absorption spectra in the range 2200-7000 A.4 P randtl
expressed the hope that t he results in solution would
stimulate further theoretical interpretation.
A comparison between theory and experiment was
given for the spectrum of Tm2(S04)3·8H20 in 1937,6
using the methods of Condon and Shortley.6 However
from the standpoint of computation, the complete
treatment of more complex configurations was n ot
practical until the development of the tensor operator
methodsof Racah. 7 Thus, the investigation of the spec-

t rum of Nd3+ in N d(Br03)s·9H20 b y S atten in 19538
was apparently the first attempt to analyze the states
resulting from more than two equivalent f electrons
assuming Russell-Saunders coupling. Subsequent studies (for example see Refs. 9 and 10) have yielded an
intermediate coupling treatment of several of the lowlying levels in the...