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The VUV $4f^{n-1}5d\text{−}4f^n$ luminescence and luminescence excitation spectra of ${\mathrm{Gd}}^{3+}$ $(n=7)$ in ${\mathrm{LiGdF}}_4$, ${\mathrm{GdF}}_3$, ${\mathrm{LiYF}}_4:{\mathrm{Gd}}^{3+}$, and ${\mathrm{YF}}_3:{\mathrm{Gd}}^{3+}$, and of ${\mathrm{Lu}}^{3+}$ $(n=14)$ in ${\mathrm{LiLuF}}_4$, ${\mathrm{LuF}}_3$, and ${\mathrm{LiYF}}_4:{\mathrm{Lu}}^{3+}$ have been analyzed with high spectral resolution. In systems with intermediate electron-phonon coupling, zero-phonon lines, and phonon sidebands were observed. The excitation spectra of dilute systems exhibit rich fine structure originating from electronic origins of transitions and their phonon replica. Theoretical calculations explicitly taking into account a microscopic model of the crystal field and the crystal lattice vibrational spectra agree well with experimental data and are the basis for a safe analysis of the spectra.

Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.

The main goal of this study was creating multifunctional nanoparticles based on rare-earth doped LaF₃ nanocrystals, which can be used as fluorescence thermal sensors operating over the 80–320 K temperature range including physiological temperature range (10–50°C). The Pr³⁺:LaF₃ (CPr = 1%) microcrystalline powder and the Pr³⁺:LaF₃ (CPr = 12%, 20%) nanoparticles were studied. It was proved that all the samples were capable of thermal sensing into the temperature range from 80 to 320 K. It was revealed that the mechanisms of temperature sensitivity for the microcrystalline powder and the nanoparticles are different. In the powder, the ³P₁ and ³P₀ states of Pr³⁺ ion share their electronic populations according to the Boltzmann and thermalization of the ³P₁ state takes place. In the nanoparticles, two temperature dependent mechanisms were suggested: energy migration within ³P₀ state in the temperature range from 80 K to 200 K followed by quenching of ³P₀ state by OH groups at higher temperatures. The values of the relative sensitivities for the Pr³⁺:LaF₃ (CPr = 1%) microcrystalline powder and the Pr³⁺:LaF₃ (CPr = 12%, 20%) nanoparticles into the physiological temperature range (at 45°C) were 1, 0.5, and 0.3% °C⁻¹, respectively.