Spectroscopic experimental and theoretical study of Uranyl(VI) in an aqueous system - Molecular modelling meets environmental protection

Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS) and cryo-TRLFS are sensitive tools for $\mathit{\text{in}}\mathit{\text{situ}}$ speciation of low-level uranium in aqueous samples, including natural waters. To tailor, often ill-conditioned (i.e., leading to ambiguous interpretations), multi-linear analysis, first-principles based theoretical computation (Molecular Dynamics and Quantum Chemistry) of luminescence spectra would be beneficial. We present a methodology to simulate TRLFS and cryo-TRLFS spectra and present vibrationally resolved luminescence spectra for aquo complex [UO${}_2$(H${}_2$O)${}_5$]${}^{2+}$(aq). Comparison to experimental data, interpretation of spectra in the terms of a minimal non-redundant set of spectroscopic parameters (peak spacing \omega, the 0’ $\to$ 0 peak position T${}_{00}$, envelope shape parameter \Delta R, average peak width \sigma and luminescence life-times) and shifts due to ligand coordination are discussed. The minimum theory-experiment deviation in T${}_{00}$ (exp. $\sim$ 20 485 cm${}^{-1}$) has been reported for SORECP/TD-DFT with LB$\alpha$ functional - 20 cm${}^{-1}$, 90 cm${}^{-1}$ and 100 cm${}^{-1}$ for different models, a similar level of agreement has been met for \omega${}_{gs}$. The RMS along configuration space sampling CMD trajectory for T${}_{00}$ corresponds well to \sigma. Preliminary predictivity study for a small set of uranyl complex species and comparison of pseudo-potential (SORECP) and all-electron results for [UO${}_2$(H${}_2$O)${}_5$]${}^{2+}$(g) are appended.