MnO4- and MnO42- molecular centers in cubic lattice: near infrared luminescence and resonance Raman spectra

We report the first observation of the near-infrared luminescence in RbI cr ystals doped with the MnO42- (manganate) and MnO4- (permanganate) ions. NIR luminescence spectra of the MnO4- and MnO42- ions show similarity in both the spectral region (8500-11 000 cm(-1)) and the appearance of well-resolve d vibronic structure at 4 K caused by the electron coupling with the bendin g (e) modes of the impurity ions. This fine structure is considered as a re sult of e circle times e and t(2) circle times e Jahn-Teller effect in the ground and excited electronic states, respectively. MnO42- NIR luminescence is attributed to the d-d (T-2(2) --> E-2) transition of a single d-electro n of Mn6+.. The origin of the luminescence in case of MnO4--doped iodides i s connected with the transient Mn6+ state, which is generated by the illumi nation-induced charge transfer process. The possibility of thermal populati on of Mn d-orbitals in case of MnO4- ion is also discussed. (C) 2001 Elsevi er Science B.V. All rights reserved.