Two-photon excitation of the4f5dband ofPr3+and interconfigurational energy transfer inLaF3:(Pr3+,Gd3+)

Two-photon stepwise excitation of the 4f5d band of ${\mathrm{Pr}}^{3+}$ using as a real intermediate level ${}_{}{}^1{}_{}{}^{}\mathrm{D}_2^{}{}_{}{}^{}$ state is demonstrated in a Pr- and Gd-doped ${\mathrm{LaF}}_3$ crystal. Strong fluorescence arising from the ${}_{}{}^6{}_{}{}^{}\mathrm{P}_{7/2}^{}{}_{}{}^{}$ level of ${\mathrm{Gd}}^{3+}$ provides the first evidence of interconfigurational energy transfer between ${\mathrm{Pr}}^{3+}$ and ${\mathrm{Gd}}^{3+}$ ions in a solid. The mechanisms involved in this energy transfer are discussed.