Journal of the Less-Common Metals, 93 (1983) 107-112 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR 107 zyxwvutsrq JUDD-OFELT PARAMETERS AND CHEMICAL BONDING* CHRISTIAN K. JORGENSEN and RENATA REISFELDt Dbpartement de Chimie MinCrale, Analytique et Appliqude, C’niuersitP de Gent?ue, CH 1211 Geneva 4 (Switzerland) (Received January 21,198s) Summary The three Judd-Ofelt intensity parameters for erbium(II1) are given in 17 different environments. The Q, parameter is strongly affected by covalent chemical bonding. In contrast, the Qs parameter is related to the rigidity of the medium in which the ions are situated. The spectroscopic properties of lanthanides in non-metallic compounds strongly imitate those of the monatomic entities with one partly filled shell (4f)q. The levels are quite crowded (for 4 = 4-10) in the UV, but the identification of excited J levels below 25000 cm- ’ is essentially complete [l, 21. Among the 41 levels of (4f)’ ’ erbium(III), 24 are predicted to lie below 40 000 cm ’ and all have been found with the exception of two close to 33 000 cm- ‘. Although severe configuration interaction effects might be expected, the energies are well described by the theory for intermediate coupling in fq in atomic spectra expressed in the simplest form with three Racah parameters of interelectronic repulsion and the Land& parameter of spin-orbit coupling. Even more surprisingly the intensities of absorption bands and the radiative transition probabilities (in both absorption and emission spectra) can also be described using only a few parameters. Spectra of condensed matter (solutions and vitreous and crystalline solids) are generally discussed in terms of the oscillator strength P (which is also denoted f by many workers) which is equal to 4.32 x 10 9 times the molar extinction coefficient Eintegrated over the wavenumber range of the transition. If the absorption band is a gaussian error curve with maximum Ed and halfwidth 6 in reciprocal centimetres, P = 9.2 x 10 9 c,6. It was shown by Einstein in 1917 (on very general thermodynamic grounds and assuming the existence of photons of energy hv) that the radiative mean lifetime 5 (or half-life t,,, = 0.6937) is inversely proportional to P(hv)‘. In most transition group compounds the radiative lifetime is of minor concern because of the very effective competition from non-radiative de-excitation [Z]. *Paper presented at the Sixteenth Rare Earth Research Conference. The Florida State University, Tallahassee, FL, U.S.A., April 1%21,1983. t Permanent address: Department of Inorganic Chemistry. Hebrew University, Jerusalem, Israel. 0022.5088/83/$3.00 c Elsevier Sequoia/Printed in The Netherlands