Analysis of the Spectra of Tripositive Praseodymium in Ethylsulfate Crystals

In the first portion of this paper a theoretical calculation is presented for the ``free‐ion'' spectrum of Pr3+ (4f2). A least‐squares calculation is made to obtain a set of Slater and spin‐orbit parameters that gives a theoretical spectrum in closest possible agreement with the observed absorption spectrum of Pr3+ (4f2) in ethylsulfate crystals. The disagreement between the calculated and observed spectrum may be explained as due primarily to the neglect of the configuration interaction in the ``free‐ion'' calculation, and to a much smaller extent as due to the effect of the lattice environment surrounding the Pr3+ (4f2) ion.In comparing the spectrum of Pr3+ (4f2) in ethylsulfate crystals with the spectrum of the same ion in other crystals, the shift in energy of the J levels may be explained as due to the difference in chemical bonding in the various crystals. This ``chemical bonding'' shift may be accounted for by a simple change in the Slater and spin‐orbit parameters.Assuming that the local symmetry ...