Luminescence concentration quenching of ¹D₂ state in YPO₄:Pr³⁺

Under selective excitation of the ³P₀ level of the Pr³⁺ ion in YPO₄, the emission spectra and fluorescence decay curves were measured at different concentrations and temperatures. The origin of the spectral line located at 16318 cm^-1 (612.8 nm) was discussed and attributed to the ¹D₂ → ³H₄ transition. The process of concentration quenching for the ¹D₂ state was also studied. Using the Inokuti-Hirayama model, the non-exponential fluorescence decay curves of the ¹D₂ level were fitted. The result shows that dipole-quadrupole interaction between Pr³⁺ ions, which causes ¹D₂ → ¹G₄ and ³H₄ → ³F₄ cross-relaxation, results in the quenching of ¹D₂ emissions.