Electronic Properties of undoped $LiBaAlF_6$ Single Crystals: Far-Ultraviolet Optical, Luminescence, and X-Ray Photoelectron Spectroscopy Studies

The electronic structure properties of undoped single crystals of LiBaAlF6 (LBAF) were determined using low-temperature (T=10 K) time-resolved far-ultraviolet (3.7–40 eV) synchrotron radiation spectroscopy, calculations for the spectra of optical functions, and x-ray photoelectron spectroscopy. The bandgap of the investigated compound was found at Eg=12.3 eV, the energy threshold for creation of the unrelaxed excitons at En=1=11.6 eV, and the low-energy fundamental absorption edge at 11.0 eV. The subnanosecond photoluminescence emission band at 6.6 eV in LBAF single crystal is due to radiative valence-core transitions 2p F−→5p Ba2+