Photoluminescence spectra and vibrational structures of the srs:ce³⁺ and srse:ce³⁺ phosphors

The details of photoluminescence and excitation spectra of powder phosphors were obtained at various temperatures between 6 and 300 K. At 300 K, two emission bands originating from the ²T_2g(5d)→²F_7/2,²F_5/2(4f) transitions are observed at 480 and 535 nm for SrS:Ce³⁺ and at 470 and 527 nm for SrSe:Ce³⁺, respectively. In the excitation spectra, bands corresponding to the ²F_5/2(4f)→²2T_2g(5d) transition are observed at 433 (SrS:Ce³⁺) and 430 nm (SrSe:Ce³⁺), and plateaus due to the fundamental absorption of the host crystals in higher energy region. The vibrational structures on the emission and excitation bands are analyzed by the use of energy matrices in order to determine the coupling constant of spin-orbit interaction and the crystal field parameters V₄^(f), V₆^(f) for the 4f orbit.