Abstract
The 20K luminescence spectrum of Cs2NaHoCl6: TmCl3- 6 differs from that of Cs2NaHoCl6 in that three additional transitions are observed in the region below 21 500 cm-1. These are assigned to the 3 F 3, 3 H 4, 3 H 4, 3 H 53 H 6 transitions of the TmCl3- 6 ion from a comparison with the luminescence and absorption spectra of Cs2NaTmCl6. The different luminescence behaviour of Cs2NaHoCl6: TmCl3- 6, Cs2NaTmCl6 and Cs2NaGdCl6: TmCl3- 6 is rationalized.