Abstracts 2002

Abstract of Publication No. 437

Oliver S. Wenger, Sophie Bénard and Hans U. Güdel
Crystal Field Effects on the Optical Absorption and Luminescence Properties of Ni2+-Doped Chlorides and Bromides: Crossover in the Emitting Higher Excited State
Inorg. Chem. 41, 5968-5977 (2002)      Full Text (PDF)      DOI-Link     

Abstract: Single crystals of CsCdCl3, CsCdBr3, CsMgBr3, and MgBr2 doped with 0.1/5% Ni2+ were grown by the Bridgman technique and studied by variable-temperature optical absorption and luminescence spectroscopies. At cryogenic temperatures all these systems are dual emitters; i.e., they emit light from two distinct, thermally nonequilibrated excited states. The emitting higher excited state is 1T2g in Ni2+:CsCdCl3 and Ni2+:CsCdBr3 and 1A1g in Ni2+:CsMgBr3 and Ni2+:MgBr2. This crossover manifests itself in a change from red broad-band to yellow sharp-line luminescence, and it is rationalized on the basis of crystal field theory. Temperature-dependent luminescence as well as two-color pump and probe experiments reveal that in Ni2+:CsMgBr3 and Ni2+:MgBr2 the 1T2g state lies only about 70 and 170 cm–1, respectively, above 1A1g. The effect of crystal field strength on thermally activated nonradiative multiphonon relaxation processes in the bromides is examined for both 1A1g/1T2g higher excited state and 3T2g first excited-state emission. Two-color excited-state excitation experiments are used to monitor Ni2+ excited-state absorption transitions originating from 3T2g.

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