Chemical Physics ELSEVIER Chemical Physics 201 (1995) 321-342 Electronic absorption spectra, optical line strengths, and crystal-field energy-level structure of Nd 3÷ in hexagonal [Nd(H20) 9](CF3SO3) 3 John R. Quagliano 1, Gary W. Burdick, Deborah P. Glover-Fischer, F.S. Richardson * Department of Chemistry, University of Virginia, Charlottesville, VA 22901, USA Received 27 June 1995 Abstract Optical absorption measurements are used to locate and assign 79 crystal-field (Stark) levels split out of the 4f 3 electronic configuration of Nd 3+ in single crystals of neodymium nonahydrate tris(trifluoromethanesulfonate), [Nd(H20)9](CF3SO3)3, denoted hereafter as NdTRF. Line strengths are determined for 56 transitions between Stark levels. Single crystals of NdTRF have hexagonal, P63/m(C6Zh) space-group symmetry, and each Nd 3+ ion is coordinated to nine water molecules in a slightly distorted tri-capped trigonal prism structure of C3h symmetry. The energy-level structure of 4f 3 (Nd 3+ ) in NdTRF is analyzed in terms of a model Hamiltonian that includes consideration of both one-electron crystal-field and two-electron correlation-crystal-field interactions, the latter interactions making important contributions to the energy- level structures of several 4f 3 [SL]J multiplet manifolds. Line strength data obtained for NdTRF is analyzed in terms of a general 4f ~ 4f transition intensity model in which the details of the 4f-electron/crystal-field/electric-dipolar radiation-field interactions are represented in parametric form. The derived parameters provide information about structural properties and interaction mechanisms that contribute to 4f ~ 4f transition intensities. The general crystal-field and intensity parameters are further analyzed in terms of a set of 'intrinsic' parameters that are related to contributions from individual Nd3+-OH2 pairwise interactions. 1. Introduction A considerable number and variety of spectro- scopic studies have been carried out on aquo coordi- nation complexes of trivalent lanthanide ions (Ln 3+) in solution and in crystals. The optical absorption " Corresponding author. i Present address: CST-2 Mail Stop E535, Advanced Optical Systems Development, Chemical Science and Technology Divi- sion, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. spectra of Ln3+(aquo) complexes in solution were studied and characterized by Carnall and co-workers [ 1] nearly 30 years ago. Results obtained from those studies yielded considerable information about the 4f N [SL]J multiplet structures of fully hydrated Ln 3÷ ions in aqueous solution. Baricenter energies and total oscillator strengths of transitions between ground and excited multiplet manifolds were deter- mined, and parametric analyses of the oscillator strength data in terms of the 3-parameter Judd-Ofelt intensity model [2,3] for lanthanide 4f--* 4f transi- tions (between J-multiplet manifolds) yielded inten- 0301-0104/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSD10301-OIO4(95)OO260-X