Spectra analysis of Tm3$^+$ in K2YF5

RADIOCHEmission and absorption spectra of Tm3+ in single crystal K2YF5 with different concentrations are reported and analyzed. The nonexponential feature of the fluorescence decay of D-1(2), level for the high concentration sample indicates the existence of a cross-relaxation process. Energy level simulation has been carried out by using a phenomenological model with 16 parameters accounting simultaneously for the free ion and crystal field (CF) effects. A good fit was achieved with a root mean square deviation sigma = 18 cm(-1). The free ion and CF effects were then discussed by comparing the available data of K2YF5:Nd3+, LiYF4:Tm3+ and LiYF4:Nd3+