The absorption spectrum of a thin film of uranium(III) formate was measured at 4 and 300 K in the 4000-23000 cm-1range. The energy levels of U3+were assigned and fitted to a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions at the C3vsymmetry site. Ten energy level parameters were varied simultaneously in least-squares adjustments yielding a mean error of 23 cm-1. The analysis enabled the determination of the crystal-field parameters and the assignment of 49 crystal-field levels. The calculated total splitting of the ground level is equal to 520 cm-1. An analysis of the 5f3→5f3band intensities based on the Judd-Ofelt theory is presented.
Karbowiak, M., & Drozdzyński, J. (2000). Absorption spectrum analysis of uranium(III) formate. Journal of Alloys and Compounds, 300, 329–333. https://doi.org/10.1016/S0925-8388(99)00733-1