C.K. Jørgensen

Judd-Ofelt parameters and chemical bonding

Abstract The three Judd-Ofelt intensity parameters for erbium(III) are given in 17 different environments. The Ω 2 parameter is strongly affected by covalent chemical bonding. In contrast, the Ω 6 parameter is related to the rigidity of the medium in which the ions are situated.

Fluorescence of europium(III) in a flouride glass containing zirconium

Abstract Europium(III) incorporated in a new zirconium barium flouride glass shows 14 luminescent transitions (at 300 K) from 5 D J ( J = 0,1,2,3) to 7 F J ( J = 0,1,2,3,4) which are compared with Judd-Ofelt parameters for induced electric dipolar radiation, as well as for calculated magnetic dipolar transition probabilities.

Split photo-electron signals from the unique closed-shell cation lanthanum(III)

Abstract The multiple signals in the 3d region of seven lanthanum(III) compounds are explained by the possibility of simultaneous transfer of an electron from the neighbour atoms to the empty 4f shell during the ionization. They cannot be due to monatomic shake-up.

Photostable solar concentrators based on fluorescent glass films

Efficient luminescent solar concentrators (LSC) were prepared by deposition of organically modified sol-gel films doped by photostable perylimide dyes on plexiglas substrates. The absorption spectra of these dyes extends from 420 to 620 nm covering the visible part of the solar spectrum and the emission is between 550 and 750 nm, close to the optimum response of silicon and gallium arsenide solar cells. The efficiency of this type of collector was calculated from the absorption coefficients, quantum efficiency of the fluorescence and the overlap between emission and absorption spectra by the method of Monte-Carlo and found to be close to 20%. Optimum concentrations are shown to be strongly dependent on the extent of overlap between the absorption and the emission spectra, which also appears to be the limiting factor in respect to the efficiency of the concentrator.

Influence of the ligands on 3d photoelectron spectra of the first four lanthanides

Abstract The detailed structure of the 3d photoelectron signals of cerium(III), praseodymium(III) and neodymium(III) is mainly due to J -level distribution in intermediate coupling of 3d 9 4f q ( q = 1, 2, 3), superposed on satellites (due to electron transfer) as known from lanthanum(III) compounds. In the latter case, the two comparable phenomena, photoelectron satellite intensity and nephelauxetic effect are better indicators of the covalent bond than two other phenomena, satellite energy separation and electron transfer energy.

Optical transition probabilities of Er3+ in fluoride glasses☆

Abstract Lead-based fluoride glasses of the system PbF 2 GaF 3  M F 2 ( M = Zn or Mn) doped by trivalent erbium were prepared by melting and quenching of the appropriate fluorides under inert atmosphere. Optical spectra of the glasses with and without manganese reveal identical characteristics in the near ir region of the spectrum. In the near uv and visible part, the manganese-containing samples show higher oscillator strength, probably due to interaction between Mn 2+ and Er 3+ . Radiative and nonradiative characteristics of the glasses were computed, using the Judd-Ofelt method. Laser transitions of the glasses were predicted.

Transition probabilities of europium(III) in zirconium and beryllium fluoride glasses, phosphate glass, and pentaphosphate crystals

Abstract Eigenvectors of Eu 3+ were obtained by a least-squares fitting procedure to the measured transitions from the two lowest J levels to a multitude of excited levels up to 41 000 cm −1 . The Judd-Ofelt parameters Ω t (t = 2, 4, 6) were obtained by comparison between the U (t) calculated from the eigenvectors, and the observed oscillator strengths. Radiative transition probabilities and branching ratios were evaluated for the excited states 5 D J (J = 0, 1, 2, 3) and 5 L 6 to 7 F J . The agreement between the calculated and observed lifetimes and branching ratios is better in oxide glasses than in the pentaphosphate crystal and fluoride glasses. This can be understood on the basis of the higher variety of sites and hence, better averaging.

The comparison of calculated transition probabilities with luminescence characteristics of erbium(III) in fluoride glasses and in the mixed yttrium-zirconium oxide crystal

Abstract Fluorozirconate glasses containing 2 mole% ErF3 were prepared by melting the binary fluorides with ammonium bifluoride under an atmosphere of carbon tetrachloride and argon at 850°C. Absorption spectra of these glasses were obtained and the Judd-Ofelt parameters were calculated. Emission spectra and lifetimes of erbium in fluorozirconate glass, in lead-gallium-zinc fluoride glass, and in yttrium-zirconium oxide crystal were measured and compared with the theoretical calculations. Laser emission lines in these materials are deduced from these measurements. It is suggested that materials doped with erbium may serve as light sources for fiber optic waveguides made from the undoped materials.

Laser-induced luminescence of rare-earth elements in natural fluor-apatites

Abstract The luminescence spectra of naturally occurring fluor-apatites containing traces of rare-earth elements have been compared with synthetic fluor-apatites to which single rare-earth elements have been intentionally added. Comparison of the laser-induced spectra obtained after different time delays allows identification of the following luminescence centers: Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, Er3+, Tm3+, Yb3+ and possibly Yb2+. The technique described here allowed for the first time to detect the luminescence of Pr3+, Eu3+, Er3+, Tm3+ and Yb3+ in natural apatites. Our results were compared with those obtained by ICP and correspondence was observed between the two methods. Our findings allow non-destructive detection by laser light of the different rare-earth elements in apatite minerals.

The quantum numbers of the fluorescent state of the uranyl ion

Abstract A close analysis of the relative importance of spin-orbit coupling and of one-electron energy differences in the 5f shell, combined with spectroscopic data on uranyl ions in glasses and crystals, suggests the lowest excited level to have Ω = 4, even parity and no well-defined S and Λ.