Spectra and Quantum States of the Europic Ion in Crystals. II. Fluorescence and Absorption Spectra of Single Crystals of Europic Ethylsulfate Nonahydrate

Abstract

From the polarization properties of the fluorescence spectrum of single crystals of europic ethylsulfate nonahydrate it was possible to determine the multipole character of transitions, the energies and quantum nature of the seven levels of the ground state multiplet of the europic ion, and the group character of the sublevels into which these states are split by the crystal field. Such an analysis was made of all pure, uncoupled electronic transitions in the fluorescence spectrum. The analysis revealed that the rare earth ion is predominantly perturbed by a field of D3h symmetry, arising from the water molecules of hydration immediately surrounding it. Upon this field is superimposed a weaker one of lower symmetry, C3h, arising from the lattice as a whole. All transitions involving a change of J of one appeared as magnetic dipole radiation. All others appeared as forced electric dipole transitions, including one which would have been fully allowed as a magnetic dipole transition. A similar analysis of the absorption spectrum in the near ultraviolet was only partially successful because of the superposition of the split levels of some of the upper states. It was in accord with the analysis of the fluorescence spectrum and from it was determined the multipole nature of the transitions and the quantum nature of some of the more isolated upper states.