Temperature dependence of the R1 linewidth in Al2O3:Mn4+: A spectral hole-burning and FLN study

► Temperature dependence of the R1 linewidth in Al2O3:Mn4+ is investigated. ► Optical hyperfine structure in transition metal ion doped solid is observed. ► Electron-phonon coupling is strong due to covalency of Mn-O bond. ► Pseudo-local modes are responsible for two-phonon Raman scattering above 50 K.