Luminescence of cerium(III) inter-shell transitions and scintillator action

Abstract

Cerium(III) energy levels and photophysics represent an intermediate status between d-group behavior and the other lanthanides showing narrow absorption bands and luminescence bands reminiscent of 4f q configuration atomic energy levels. Once the energetic separations of 0.5 to 2 eV of 5d-like orbitals are recognized to provide huge Stokes shifts and rather wide emission bands, it is also obvious that Ce(III) does not have a standard symmetry of ligating atoms (e.g. coordination number N = 9 and D3h known from aqua ions and anhydrous LnCI3 and LnBr3) but N is often 12, I 1,8, 7 or 6 (and rarely octahedral, as frequent in the d groups), 8 in irregular symmetries perhaps most typical. Scintillators for detecting very high kinetic energies (approaching the relativistic regime of photons and particles with very low rest-mass) involve closed shells, such as 4f and 5d in lutetium(Ill); barium 5p, 5d and 4f in highly electrovalent barium(II) in transparent crystals; and perhaps 4fand 6s in hafnium(IV) and tantalum(V) fluorides.

Luminescent Hybrid Material Based on a Clay Mineral

“…Lanthanide ions, especially Eu 3+ and Tb 3+ , have in the past been demonstrated to afford efficient luminescence on doping into porous matrixes, such as sol−gel materials and zeolites. , However, a principal bottleneck of merely rare earth doped host−guest systems, for, e.g., photoluminescence (PL) driven light-generating purposes, is the weak absorption of the rare earth ions above 250 nm, caused by the forbidden nature of the f−f transitions. Furthermore, water is encountered in most of these matrixes, leading to disadvantageous deactivation of the excited states via high-energy vibrations.…”