Quantum extension of the Judd–Ofelt theory: Static dipole effects with application to Eu3+ in water

We propose a quantum extension of the Judd–Ofelt (JO) theory to include static dipole contributions in the description of 4f→4f electric dipole transitions. By treating the Ln³⁺ ion and its ligand environment as a unified quantum system, our approach unifies the conventional JO and Dynamic Coupling (DC) formalisms. The model is applied to Eu³⁺ in aqueous solution, where water molecules possess permanent dipole moments. Experimental and computational results show that only the ⁵D₀→⁷F₂ transition intensity increases with NO₃⁻ concentration, despite the anion not entering the first hydration shell. This effect is attributed to enhanced long-range dipolar fields, which selectively influence the Ω₂ parameter. The findings highlight the role of static dipoles in modulating hypersensitive transitions and offer a refined framework for interpreting luminescence in complex environments.