Conversion of VUV to visible light and the structure of the 5d levels in K5Li2LaF10:Tb

Abstract Upon UV–VUV excitation terbium doped K 5 Li 2 LaF 10 emits white light coming from the 5 D 3 and 5 D 4 multiplets for content of Tb 3+ up to 10 at%. For higher concentrations (80 and 100 at%) the emission becomes green. In excitation spectrum, recorded at 12 K, the positions of the zero-phonon lines are not well determined. The spin allowed f–d transitions in this spectrum are similar to the cerium one in K 5 Li 2 LaF 10 : Ce 3+ , as van Pieterson proposed in the frames of Dorenbos’ model. The maxima of these terbium f–d transitions are found at: 46,976, 57,124, 59,404, 60,629 and 67,110 cm −1 . The lowest forbidden, high-spin d band is situated at 39,193 cm −1 . The lifetime of the 5 D 4 multiplet is 7.5 ms and does not depend on the terbium concentration, but the 5 D 3 lifetimes are strongly influenced and amount to: 2710, 2130, 14.1, 9.5 μs for 2, 10, 80, 100 at% of terbium, respectively. This is in agreement with the colour rendering of these samples.