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.
Highlights
Rare-earth metal ions can serve as centers in efficiently fluorescent artificial complexes [1] or natural minerals [2]
The comparison of the results provided by the three evaluation methods unambiguously indicated that the approach assuming comparable decay and equilibrium rate constants proved to be the most reliable
Stability constants, individual absorption and emission properties of cerium(III)-fluoro complexes were carefully determined by steady-state spectrophotometry and spectrofluorometry, as well as time-resolved emission measurements
Summary
Rare-earth metal ions can serve as centers in efficiently fluorescent artificial complexes [1] or natural minerals [2]. Parity allowed absorptions in the UV region, originating from 4f-5d transitions, make it possible to detect the electronic changes during complexation at relatively low concentrations. Cerium(III)-doped or based materials are among the most usable and efficient scintillators, owing to their fast and intensive fluorescence [3,4,5,6,7,8,9,10,11]. The ultraviolet (visible) absorption spectrum of cerium(III) ions with a [Xe]4f1 electron configuration is determined by the spin and symmetry allowed 4f–5d transitions, instead of weak f-f absorptions characteristic of lanthanides. The spectrum is complicated because the 4f1 subshell is split by spin-orbit coupling about 2000 cm−1: 2F → 2F5/2 + 2F7/2
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