Anharmonic charge transfer vibronic states and luminescence dynamics of uranyl compounds

An adiabatic potential is constructed for uranyl (UO2)2+ with inclusion of both harmonic and anharmonic types of charge transfer – lattice interactions. Such an approach is used for modeling charge transfer vibronic transitions of uranyl in crystals. It is shown that anomalous hot bands observed in Cs 2 ZrCl 6 : UO 2 Cl 4 2 - are due to a double-well potential of harmonic charge transfer vibronic excitons (CTVE-I) and anharmonic charge transfer vibronic excitons (CTVE-II). In order to explain an uncommon doublet in the absorption spectrum previously reported for UO 2 Cl 4 2 - in Cs2UO2Cl4 crystal, an anharmonic CTVE tunnel model is proposed based on the expected tunneling between CTVE-I and CTVE-II.