Optical vibronic spectra of aggregates in Eu$^{\mathbf2+}$ -doped KCl and KBr crystals

Abstract

The vibronic structure on the optical absorption, emission, and excitation spectra of aggregates in Eu$^{2 + }$-doped KCl and KBr crystals has been obtained. The crystals were annealed at 435K. During the aggregation process, four groups of narrow bands were found in KCl:Eu$^{2 + }$ and two, in KBr:Eu$^{2 + }$, which were considered as the signature of different Eu$^{2 + }$-ion aggregated phases. The vibration frequency for each group is very similar.