Luminescence excitation mechanisms of rare earth doped phosphors in the VUV range

Progress in the development of new luminescent materials is directly related to our understanding of physical processes of energy absorption and relaxation in solids. As far as the VUV energy is concerned, the most suitable materials are probably the large band gap inorganic lattices activated by rare earth ions. Optical excitation in these systems result either in a direct excitation of the luminescence center or an excitation of the host lattice which partly transfer the energy to the emitting levels of the activator. Every steps of the luminescence mechanism enter in competition with nonradiative losses or undesired luminescence which have to be minimized in order to get a high luminescence efficiency. Determination of the dominant transfer and energy loss mechanisms can be performed by time resolved luminescence spectroscopy using UV-VUV synchrotron radiation (SR) excitation. We report here, the result of studies of a large number of rare earth doped materials, performed in the frame of programmes for search of new efficient VUV phosphors and scintillators. The experiments were performed using XUV-VUV SR from SuperAco and DCI storage rings at LURE.