Europium in the ultraphosphate lattice: Polarized spectra and structure of EuP5O14

Abstract

The polarized emission and absorption spectra of single crystals of europium ultra(penta)phosphate, EuP₅O₁₄, were measured and interpreted. Most of the observed transitions were identified and the energy level structure of the ⁷F multiplet defined. The over‐all site symmetry is found to be extremely low (C₁), but in the immediate vicinity of the Eu³⁺ ion the local symmetry appears to deviate little from C_2v. Crystal field calculations were performed for such symmetry and gave a respectable fit to the observed Stark splittings of the ⁷F multiplet. A simple structural model for the first coordination shell of the Eu³⁺ ion is proposed, consistent with the spectroscopic behavior and with the signs and relative magnitudes of the calculated crystal field parameters. Finally, the decay times of the ⁵D₀ and ⁵D₁ emitting states of the ion were calculated and found to be consistent with measurement.