Radiative transitions to localized Eu states in Pb1−xEuxTe solid solutions

Two types of radiative transitions were observed in the low-temperature photoluminescence spectra of Pb_1−x Eu _x Te (0 ≤ x ≤ 0.09) solid solutions: an intense line corresponding to the transitions from the conduction to the valence band and a series (up to 15) of narrow lines corresponding to the transitions from the hybridized conduction band to the split Eu³⁺ levels. The intensity of the discrete lines increases with x, and their energies (and intensities) weakly depend on the temperature. The absorption and emission of the discrete lines are caused by the 4f ⁷(⁸ S _7/2) ↔ 4f ⁶(⁷ F _J )[L ₆⁻ + 5dt _2g ] transitions.