Effect of the Electron−Phonon Interaction on the Luminescence Properties of Iron Ions in YAG Crystal

High-resolution photoluminescence spectra of Fe:YAG crystals were recorded in the temperature range 10-150 K with different excitation energies, ranging from the band gap energy (6.88 eV) down to selective excitation of Fe(3+) ions (2.40 eV). Iron levels fine structure is found in the zero phonon lines, whose characteristics hint at the presence of the doping Fe(3+) ion in the tetrahedral site with a dynamic Jahn-Teller effect inherent in the (4)T(1) excited states. The analysis of the zero phonon interactions with acoustic phonons was achieved through linear and quadratic electron-phonon coupling models, and the Huang-Rhys factor, the Debye temperature, and the electron-phonon coupling were calculated in the framework of the Debye approximation by including only the Raman two-phonon process. The interactions with lattice phonons were studied, and the results were found to be correspondent to the expected results from previous vibrational data.