Phonon spectra of stoichiometric rare-earth compound of EuGa2S4

Investigations of EuGa₂S₄ have been done on the photoluminescence (PL) related to the transition between 4f⁶5d and 4f⁷ configuration of the Eu²⁺ ion and its excitation (PLE) spectra, Raman scattering and infrared absorption. The energies of phonons coupled to the ground and the excited states of the transition are analyzed to be 34 and 19 meV from the shapes of the PL and PLE bands, respectively. The former corresponds to the energy of the Raman line showing the highest intensity. The latter is close to the value obtained from analysis of the temperature dependence of the half width of the PL band. These correspondences indicate that the relevant emission of EuGa₂S₄ surely has phonon-terminated character.