Excited state absorption of the Cr~(6+)O_(2-) center in Li_2B_4O_7 glass

摘要

We present excited state absorption (ESA) measurements of the Cr:Li_2B_4O_7 glass (Cr:LBO-glass) along with preliminary interpretation. The most distinct feature in the ESA characteristics is connected with the presence of chromium in its hexe-(d~0) valence states. The Cr~(6+) ions appear to contribute in the deexcitation processes and their evidence can be seen in the ESA spectra under excitation wavelength at 308 nm. We interpret the ESA spectra detected with UV excitation in terms of transitions in the framework of Cr~(5+)O~- center which forms after charge- transfer -type absorption in [CrO_4]~(2-) group. We assume the presence of the double-electron state of the 3d~22p~4 electronic configuration together with crystal field-split states of the 3d~12p~5 configuration, both allow to reproduce the obtained ESA spectra.