Time-resolved luminescence and excitation spectroscopy of co-doped Gd3Ga3Al2O12 scintillating crystals

<jats:title>Abstract</jats:title><jats:p>Cerium doped Gd<jats:sub>3</jats:sub>Ga<jats:sub>3</jats:sub>Al<jats:sub>2</jats:sub>O<jats:sub>12</jats:sub> (GGAG) single crystals as well as GGAG:Ce single crystals co-doped by divalent (Mg<jats:sup>2+</jats:sup>, Ca<jats:sup>2+</jats:sup>) and tetravalent (Zr<jats:sup>4+</jats:sup>, Ti<jats:sup>4+</jats:sup>) ions have been studied by means of time-resolved luminescence as well as the excitation luminescence spectroscopy in vacuum ultraviolet (VUV) and soft X-ray (XUV) spectral range. Tunable laser excitation was applied for time-resolved experiments in order to obtain luminescence decay curves under excitations in Ce<jats:sup>3+</jats:sup>, Gd<jats:sup>3+</jats:sup> and excitonic absorption bands. The influence of the co-dopant ions on the Ce<jats:sup>3+</jats:sup> luminescence decay kinetics is elucidated. The fastest luminescence decay was observed for the Mg<jats:sup>2+</jats:sup> co-doped crystals under any excitation below bandgap energy indicating the perturbation of the <jats:italic>5d</jats:italic> states of Ce<jats:sup>3+</jats:sup> by Mg<jats:sup>2+</jats:sup> ions. Synchrotron radiation was utilized for the luminescence excitation in the energy range from 4.5 to 800 eV. Special attention was paid to the analysis of Ce<jats:sup>3+</jats:sup> excitation spectra in VUV and XUV spectral range where multiplication of electronic excitation (MEE) processes occur. Our results demonstrated that GGAG:Ce single crystals co-doped by Mg<jats:sup>2+</jats:sup> ions as well as the GGAG:Ce crystal annealed in vacuum reveal the most efficient excitation of Ce<jats:sup>3+</jats:sup> emission in VUV-XUV excitation range. The role of intrinsic defects in MEE processes in the co-doped as well as in the annealed GGAG:Ce single crystals is discussed.</jats:p>