Fano antiresonance in the excitation spectra of the luminescence of divalent europium

In the excitation spectra of the luminescence of ${\mathrm{Eu}}^{2+}$-doped compounds features are observed which are interpreted as Fano antiresonance lines due to interaction between the 4$f^7$ ${(}^6$ $I_J$ ${,}^6$ ${\mathrm{D}}_{\mathrm{J}}$) states and the 4$f^6$5d states. The observations can be understood on the basis of results from two-photon absorption experiments on ${\mathrm{Eu}}^{2+}$.