Excited state spectroscopy of chromium ions in various valence states in glasses

The spectral properties of different types of chromium-activated glasses are shown, discussed and interpreted. Chromium in four valence states, Cr3+, Cr4+, Cr5+ and Cr6+, is seen in the spectral characteristics of these glasses where Cr3+, Cr5+ and Cry play an important role. Trivalent chromium in octahedral coordination reveals the spectra and decays that are typical for low-field materials with a substantial participation of the site-to-site disorder. The characteristics of the Cr5+ and Cr6+ ions appeared to be more interesting. Absorption, excitation and luminescence of the pentavalent chronuum (d(1) system) in the octahedral coordination are severely affected by the Jahn-Teller effect, along with the nuances associated with that effect. The hexavalent chromium (d(1) system) in the four-fold coordination, forming the [CrO4](2-) group, is seen mostly in the excited state absorption (ESA) spectra that can be interpreted in terms of the transitions between crystal field split terms of the Cr5+O- centre, which forms after the charge transfer (CT) transition, and between one of those terms and another double-electron state of larger electron lattice coupling, which forms after two consecutive transitions of electrons via the CT transition. (C) 2002 Elsevier Science B.V. All rights reserved.