Charge-transfer bands in alkaline-earth fluoride crystals doped by Eu3+ or Y b3+ ions

Absorption, emission and excitation spectra of CaF2, SrF2, BaF2 crystals doped by Y bF3 or EuF3 impurities were studied in 1–12 eV spectral region. The intensive absorption broad bands (denoted as CT1) were observed in all cases just below the 4f–5d absorption region. Less intensive absorption bands, denoted as CT2, having energies 1.2–1.5 eV lower than those of CT1, were observed in CaF2, SrF2 crystals doped by EuF3 or Y bF3 impurities. esolution emission spectra of Eu-doped CaF2 and SrF2 crystals excited into CT1 and CT2 bands were measured. Under excitation into CT1 bands, all present Eu sites (C4v, Oh and some aggregates) were observed in emission spectra. While under excitation into CT2 bands, only the emission of C4v sites was observed.