Absorption, reflection as well as luminescence emission, excitation, and decay curves for single crystals of LuAlO 3 :Ce 3+ and LuAlO 3 :Pr 3+ grown by the Bridgman technique have been measured at various temperatures. The fluorescence spectra photo-excited over a wide energy domain ranging from the UV to the x-ray region, and the kinetics are typical of the cerium and praseodymium ions. These experimental results show that the exciton transfer to the dopant occurs at around 8 eV, and the energy transfer via sequential hole and electron trapping is dominant at higher energy. This process must be considered as the main scintillation mechanism in this crystal. The high efficiency of this mechanism is explained by the small energy difference between the 4f level of the dopant and the top of the valence band, estimated from XPS measurements.

Absorption, excitation and emission spectra and lifetime measurements in cerium-doped lanthanum fluoride single crystals were obtained using both one- and two-photon spectroscopy techniques. It is shown that two kinds of fluorescent centres are present. In weakly doped systems, a rapid fluorescence around 300 nm dominates, due to Ce3+ ions at normal sites. In heavily doped systems, an additional longer fluorescence appears at higher wavelengths due to Ce3+ ions occupying perturbed sites and acting as traps. In CeF3, the energy migrates among Ce3+ ions and is finally trapped so that only the trap emission is detected at room temperature. Significant energy losses in the fluorescence of Ce3+ at normal sites are explained by up-conversion and ionization processes and by non-radiative surface recombination phenomena for the case of strong absorption. Two-photon excitation spectra in the region of trap absorption confirm the role of traps in emission mechanisms and show narrow lines which could be vibronic structures of various kinds of traps existing in these materials.

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