Vacuum ultraviolet 5d${}^1$4f${}^9$-4f${}^{10}$ emission of Ho${}^{3+}$ ions in alkaline-earth fluorides

Abstract

Time-resolved emission, excitation as well as emission decay curves of CaF${}_2$, SrF${}_2$, BaF${}_2$ doped with HoF${}_3$ were investigated. Most intensive emission bands near 168 nm, having long decay time, belong to spin-forbidden transitions from 5d${}^1$4f${}^9$ high spin (HS) states to ground ${}^5$I${}_8$ states of Ho${}^{3+}$ ions. Weak spin allowed 5d${}^1$4f${}^9$(LS)-4f${}^{10}$ emission band at 158 nm was observed only in CaF${}_2$-Ho crystals. Spin allowed and spin-forbidden excitation bands were observed in all crystals near 166 and 155 nm respectively. Fast component of spin-forbidden emissions due to multiphonon relaxation to low-lying 4f${}^{10}$ Ho${}^{3+}$ level was observed for all crystals.

4 pages, 7 figures