Thermal shift research on the R1 and R2 lines of Cr3+-doped ZnGa2O4 spinel with a full expression

This paper gives a theoretical research on the thermal shifts of Ri (i = 1, 2) lines (corresponding to the transitions from two components of the first excited state 2E to the ground state 4A2) in ZnGa2O4: Cr3+ spinel with a full expression including both the static effect due to lattice thermal expansion and the dynamic effect owing to electron-phonon interaction. The outcomes show that the static and dynamic effects result in the thermal blue- and red-shifts, respectively. The relative importances of static effect for R1 and R2 lines are, respectively, about 26% and 27% and so the observed thermal shifts of Ri lines are thermal red-shifts. The true electron-phonon coupling parameters α' for both the Ri lines are evaluated. They are found to be about 1.36 times the corresponding apparent electron-phonon coupling parameters α acquired by considering only the dynamic effect. These results are discussed.