The luminescence of Tm2+ in strontium tetraborate

Abstract The 4f 12 5d→4f 13 emission of Tm 2+ is observed for the first time. It consists of a red band emission with vibronic structure. For a parity-allowed 4f-5d transition its decay time is long, viz. 230 μs. In addition intraconfigurational 4f 13 line emission is observed. The results are compared to 4f-5d emissions of other divalent lanthanides in SrB 4 O 7 .