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

摘要

The spectral properties of different types of chromium-activated glasses are shown, discussed and interpreted. Chromium in four valence states, Cr~(3+), Cr~(4+), Cr~(5+) and Cr~(6+), is seen in the spectral characteristics of these glasses where Cr~(3+), Cr~(5+) and Cr~(6+) 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 Cr~(5+) and Cr~(6+) ions appeared to be more interesting. Absorption, excitation and luminescence of the pentavalent chromium (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~0 system) in the four-fold coordination, forming the [CrO_4]~(2-) group, is seen mostly in the excited state absorption (ESA) spectra that can be interpreted in terms of the transitions between crystal field spilt terms of the Cr~(5+)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.