Analysis of the absorption and luminescence spectra ofU 3þ :Cs 2 NaYBr 6 single crystals M. Karbowiak a ,E.Zych a ,P.Dere n b ,J.Dro _ zd _ zy nski a, * a Faculty of Chemistry, University of Wroclaw, ul. F. Joliot-Curie 14, 50-383 Wroclaw, Poland b W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 937, 50-950 Wroclaw, Poland Received 14 October 2002 Abstract Uranium(3+)dopedCs 2 NaYBr 6 singlecrystalswitha2.1and0.09mol%U 3þ concentrationhavebeenobtainedby the Bridgman–Stockbarger method. The U 3þ ions replaced the Y 3þ ions at an octahedral site of O h symmetry. Lu- minescencespectraofthecrystalwererecordedat4.2K.Theemissionbandsobservedinthevisibleandnearinfrared regions have been assigned to transitions from the lowest components of the 4 G 7=2 and 4 F 3=2 multiplets to the crystal- field components of the 4 I 9=2 ground state. Absorption spectra were recorded in the 3900–35,000 cm 1 rangeat4.2K. Theanalysisofthesespectraenabledtheassignementof28energylevels,whichwerefittedtosevenparametersofan empiricalHamiltonianrepresentingthecombinedatomicandcrystal-fieldinteractions,witharmsdeviationof43cm 1 . Theenergiesofthemostprominentvibronicfeatureshavebeenmeasuredandassignedtothespecificvibrationalmodes of the UCl 3 6 moiety or to lattice modes. Above 14,000 cm 1 vibronic transitions associated with the electric dipole allowed 5f 3 –5f 2 6d 1 transitions were observed. The unresolved zero-phonon lines are accompanied by a number of vibrational progressions combined with the even S 1 ða 1g Þ mode. Ó 2002 Elsevier Science B.V. All rights reserved. 1. Introduction In a number of papers [1–5] the results of op- tical studies and energy level parameterisations of most of the lanthanide ions doped in elpasolite single crystals, have been reported. For the acti- nide ions the data are less comprehensive. Optical studiesoftheionsintheelpasolitehosthavebeen reported for Np 3þ [6],Am 3þ [7,8], 248 Cm 3þ [9]and U 3þ [10,11]. Crystal-field calculations have been performed for Am 3þ :Cs 2 NaLuCl 6 single crystals onthebasisof22energylevels,determinedinthe 0–22,000 cm 1 energy range from absorption and luminescence spectra. A more comprehensive set of data is available for 248 Cm 3þ diluted in Cs 2 NaYCl 6 . The application of laser selective ex- citation, excited state absorption, two-photon ab- sorption and line narrowing techniques enabled the assignment of 52 energy levels, which were fitted to the parameters of an empirical Hamilto- nianwitharmsdeviationof57cm 1 .FortheU 3þ Chemical Physics 287 (2003) 365–375 www.elsevier.com/locate/chemphys * Corresponding author. Tel. +48-71-3757333; fax +48-71- 3282348. E-mail address: jd@wchuwr.chem.uni.wroc.pl (J.Dro_ zd_ zy nski). 0301-0104/03/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0301-0104(02)01024-8