2 April 1999 Ž . Chemical Physics Letters 303 1999 76–80 Visualisation of the reliability of Judd–Ofelt intensity parameters by graphical simulation of the absorption spectrum K. Binnemans a, ) , H. De Leebeeck a , C. Gorller-Walrand a , J.L. Adam b ¨ a Coordination Chemistry DiÕision, Department of Chemistry, K.U. LeuÕen, Celestijnenlaan 200F, B-3001 HeÕerlee, Belgium b Laboratoire des Verres et Ceramiques, U.M.R. C.N.R.S. 6512, UniÕersite de Rennes I, Campus de Beaulieu, F-35042 Rennes Cedex, ´ ´ France Received 31 December 1998; in final form 5 February 1999 Abstract It is shown that graphical simulation of the optical absorption spectrum of trivalent lanthanide ions doped into glasses is a good method for checking the reliability of the Judd–Ofelt intensity parameters which are used to describe the spectral intensities of 4f–4f transitions. The method is illustrated for the absorption spectrum of trivalent holmium in the 3q Ž . y20 2 fluorozirconate glass ZBLAN:Ho . The Judd–Ofelt parameters of this system are: V s 2.25 "0.11 =10 cm , 2 Ž . y20 2 Ž . y20 2 V s 2.19 "0.15 =10 cm , V s 2.07 "0.11 =10 cm . q 1999 Elsevier Science B.V. All rights reserved. 4 6 The optical absorption spectra of the trivalent lanthanide ions in solutions and in glasses are char- wx acterised by narrow, weak absorption bands 1 . Each transition corresponds to a transition between two spin–orbit coupling levels. In general, the molar absorptivity e of these absorption bands is - 10 l mol y1 cm y1 . The majority of the transitions are induced electric dipole transitions, although some magnetic dipole transitions are observed. The inten- sity of the transitions is expressed in terms of the oscillator strength f or in terms of the dipole strength Ž D. The dipole strength of a transition expressed in ) Corresponding author. Fax: q32 16 327992; e-mail: koen.binnemans@chem.kuleuven.ac.be 2 . debye can be extracted from the absorption spec- trum, using the formula: 1 A n Ž . D s d n , 1 Ž. H 108.9 Cd n where C is the concentration of the lanthanide ion Ž y1 . Ž . mol l , d is the optical path length cm , A is the Ž Ž .. absorbance A sylog IrI and n is the 0 Ž y1 . wavenumber cm . The absorbance is related to the molar absorptivity ´ via Lambert–Beer’s law: A s ´ Cd. The dipole strength of a magnetic dipole transition can be calculated by using the 4f free-ion wavefunctions only. However, for the calculation of the dipole strengths of the induced electric dipole transitions, parameterisation is necessary. In the w x framework of the Judd–Ofelt theory 2,3 , the dipole 0009-2614r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0009-2614 99 00216-X