Explanation for the Multi-Component Scintillation of Cerium Fluoride Through the Equilibrium and Photophysical Investigation of Cerium(III)-Fluoro Complexes

Abstract

CeF3 displays favorable scintillation properties, which have been utilized for decades in various solid-state systems. Its emission undergoes multi-component decays, which were interpreted by lattice defects and so-called intrinsic features herein. This study of the complex equilibria in connection with photophysical behavior of the cerium(III)-fluoride system in solution gave us the possibility to reveal the individual contribution of the [CeIIIFx(H2O)9−x]3−x species to the photoluminescence. Spectrophotometry and spectrofluorometry (also in time-resolved mode) were used, and combined with sophisticated evaluation methods regarding both the complex equilibria and the kinetics of the photoinduced processes. The individual photophysical parameters of the [CeIIIFx(H2O)9−x]3−x complexes were determined. For the kinetic evaluation, three methods of various simplifications were applied and compared. The results indicated that the rates of some excited-state equilibrium processes were comparable to those of the emission decay steps. Our results also contribute to the explanation of the multi-component emission decays in the CeF3-containing scintillators, due to the various coordination environments of Ce3+, which can be affected by the excitation leading to the dissociation of the metal-ligand bonds.

Evidence for Participation of 4f and 5d Orbitals in Lanthanide Metal–Ligand Bonding and That Y(III) Has Less of This Complex-Stabilizing Ability. A Thermodynamic, Spectroscopic, and DFT Study of Their Complexation by the Nitrogen Donor Ligand TPEN

“…The 4f → 5d band at the longest wavelength observed in the Ce­(III) complexes shifts to longer wavelengths along the series Ce 3+ (aq) (252 nm), IDA (266 nm), EDTA (275 nm), and DTPA (297 nm), as the number of nitrogen donors is increased, paralleling the shifts of 4f → 4f transitions to longer wavelengths of other Ln­(III) ions and Am­(III) with coordinated nitrogen donors. As one would expect from covalency considerations, the latter 4f → 5d band occurs at a shorter wavelength (246.5 nm) in the CeF 3 (aq) species than for the Ce 3+ aqua ion . The shifts of the 4f → 5d bands of Ce­(III) upon complexation of more covalently binding ligands are much larger than those of the 4f → 4f transitions of Ln­(III) ions.…”

“…expect from covalency considerations, the latter 4f → 5d band occurs at a shorter wavelength (246.5 nm) in the CeF 3 (aq) species than for the Ce 3+ aqua ion. 40 The shifts of the 4f → 5d bands of Ce(III) upon complexation of more covalently binding ligands are much larger than those of the 4f → 4f transitions of Ln(III) ions. For example, the 4f → 5d band of Ce(III) at 252 nm in the aqua ion shifts to 297 nm in the DTPA complex, while the hypersensitive band at 575 nm in the Nd(III) aqua ion shifts only to 582.5 nm in the Nd(III)/ DTPA complex.…”