X-ray excited optical luminescence spectrum of Pr-doped YPO<SUB>4</SUB>

The X-ray excited optical luminescence spectrum of Pr3+ in YPO4 was investigated. In addition to the sharp line f-f transitions involving the energy levels of the 4f2 configuration of Pr3+ ion, the spectrum contains some broad groups of fluorescence lines in the ultraviolet and blue region. These groups of fluorescence are attributed to transitions from the lowest 4fI5d state at 43050 cm-1 to the 4f2 levels of the Pr3+ ion in YPO4