Optical Absorption, Emission, and Excitation Spectra of Eu²⁺ in the Alkali Halides

Abstract

The optical absorption, emission, and excitation spectra for the Eu⁵⁺ ion in the alkali halides have been investigated at room temperature. It was found that the magnitude of the 10Dq splitting of the 4f⁶5d configuration into its t_2g and e_g components caused by the cubic crystalline field follows the spectrochemical series in which the ordering of the halides appears to be determined by the magnitude of the contact interactions. The emission spectrum of the quenched samples consists in all cases of only one band whose peak position moves to shorter wavelengths as the lattice parameter increases within a given series. The excitation spectrum correlates quite well with the optical absorption and shows that the e_g level decays to the t_2g from which the fluorescence originates.