Luminescence and electronic excitations in K[Be.sub.2]B[O.sub.3][F.sub.2] crystals

This paper reports on a study of the dynamics of electronic excitations in K[Be.sub.2]B[O.sub.3][F.sub.2] (KBBF) crystals by low-temperature luminescent vacuum ultraviolet spectroscopy with nanosecond time resolution under photoexcitation by synchrotron radiation. The first data have been obtained on the kinetics of photoluminescence (PL) decay, time-resolved PL spectra, time-resolved PL excitation spectra, and reflection spectra at 7 K; the estimation has been performed for the band gap [E.sub.g] = 10.6-11.0 eV; the predominantly excitonic mechanism for PL excitation at 3.88 eV has been identified; and defect luminescence bands at 3.03 and 4.30 eV have been revealed. The channels of generation and decay of electronic excitations in KBBF crystals have been discussed.