Optical spectroscopy, thermal quenching and electron-vibrational interaction of the octahedrally coordinated Eu2+ ion in SrAl2B2O7

The spectroscopic properties of the six-fold (octahedral) coordinated Eu2+ in SrAl2B2O7 have been investigated. Relevant optical parameters such as the Stokes shift, crystal-field splitting, the centroid shift and the red-shift of the Eu2+ 4f65d1 electronic configuration have been estimated from the experimental data. Further, the Huang-Rhys factor and the effective phonon energy, which are responsible for electron-vibrational interactions are theoretically estimated for the Eu2+ ion in SrAl2B2O7. The low quenching temperature of the luminescence is connected with the thermally induced photoionization of the Eu2+ 4f65d1 electron. A cross-cutting comparative study of the optical properties of octahedrally coordinated Eu2+ in SrAl2B2O7 and in Cs2M2+P2O7 (M2+=Ca2+, Sr2+) is also presented.