Luminescence VUV spectroscopy of cerium-and europium-doped lithium borate crystals

The paper reports on a study of the luminescence of lithium borate crystals (Li6Gd(BO3)(3) doped by Eu3+ and Ce3+ ions, Li5.7Mg0.15Gd(BO3)(3): Eu, and Li6Eu(BO3)(3)) initiated by selective excitation by synchrotron radiation at excitation energies of 3.7-27 eV at 10 and 290 K. Efficient energy transfer between the rare-earth ions Gd3+ -> Ce3+ and Gd3+ -> Eu3+ was found to proceed by the resonance mechanism, as well as by electron-hole recombination. Fast decay kinetics of luminescence of the Ce3+ activator centers was studied under intracenter photoexcitation and excitation in the interband transition region. The mechanisms involved in luminescence excitation and radiative relaxation of electronic states of rare-earth ions are analyzed, and the energy transfer processes operating in these crystals are discussed.