X-ray diffraction of Ce³⁺-doped SrMgF₄ (SMF:Ce) crystals shows a superlattice structure, reflecting the distribution of Ce³⁺ polyhedra centres observed in optical experiments. Optical absorption bands and fluorescence bands from the Ce³⁺ polyhedra centres overlap in the vacuum ultraviolet (VUV) and ultraviolet (UV) regions, respectively, so that wide pumping and tuning ranges are expected for laser operation. The SMF:Ce crystals, as well as the isomorphous BaMgF₄, are candidates for a tunable laser gain material with nonlinear properties.

The optical absorption, excitation, and fluorescence bands observed in the SMF:Ce crystals at low temperatures are ascribed to five distinct fluorescent centres. Three centres have well-known Ce³⁺ optical characters, for example, fluorescence with double peaks separated by 2000 cm⁻¹ and five resolved absorption/excitation bands. These centres are assigned to Ce³⁺-polyhedra classified by weak and strong crystal fields as a consequence of the superlattice structure. The other two fluorescence bands observed in the visible region have 1.5–2 times larger linewidths than those of the former three bands. These bands are interpreted as optical transitions from complexes consisting of Ce³⁺ and one or two electrons trapped at a vacancy of the nearest neighbour F⁻ ligand ions.