Excitation spectra and fluorescent lifetime measurements of Mn2+ in CaF2 and CdF2

The excitation spectrum of the Mn2+ emission has been measured in CaF2 and CdF2. The observed excitation bands have been assigned to transitions of the Mn2+ ions in a cubic environment. The calculated values for the crystal field (Dq) and Racah parameters (B,C) are Dq = 425 cm-1 for CaF2, Dq = 500 cm-1 for CdF2 and, B = 770 cm-1 and C / B = 4.48 for both compounds. The lifetime of the fluorescent level 4T1g(4G) has been measured in both compounds at different temperatures in the range from 10 to 500 K. The lifetime thermal dependence is explained taking into account different mechanisms (purely radiative, phonon assisted, and radiationless transitions) for the decay of excited Mn2+ ions.