SITE-SELECTIVE OPTICAL SPECTROSCOPY OF CR3-2.6 AL2O3( DOPED NONSTOICHIOMETRIC GREEN SPINEL MGO)

Site-selective laser spectroscopy at low-temperature is used to analys e the fluorescence of Cr3+ in the non-stoichiometric green spinel MgO- 2.6 Ala(2)O(3). Four main kinds of sites are characterized: several mo re or less distorted strong crystal field sites responsible for E-2 -- > (4)A(2) emission lines around 690 nm with lifetimes of 20 to 5 ms an d E-2 Splitting of 26 to 120 cm(-1) Cr3+ pairs emitting at about 710 n m, and medium and weak crystal field sites responsible for T-4(2) --> (4)A(2) broad band emissions at about 750 nm and 910 nm, respectively. (C) 1998 Elsevier Science B.V. All rights reserved.