Excited state absorption of Cr3+ in K2NaScF6 and Gd3Ga2(MO4)3, M=Ga, Al

Abstract

The excited state absorption (ESA) spectra of Cr³⁺ in the elpasolite K₂NaScF₆ and the garnets Gd₃Sc₂(GaO₄)₃ (GSGG) and Gd₃Sc₂(AlO₄)₃ (GSAG) were measured from 0.3 to 1.8 μ, exclusive of the fluorescence region, using pulsed laser excitation. The two ligand field transitions ⁴T_1g(a)←⁴T_2g and ⁴T_1g(b)←⁴T_2g were located in the garnets at 9000 and 19 400 cm⁻¹ (19 200 cm⁻¹ for the elpasolite). In addition, intense UV charge transfer bands were found in the garnets, but not the elpasolite. The elpasolite spectrum confirms that major differences exist between the ESA of ²E_g and ⁴T_2gCr³⁺ excited states. A single configuration coordinate model is developed which is adequate for predicting energies but not the bandwidths of ²E_g and ⁴T_2g ESA transitions between ligand field levels.