Optical spectroscopy of Mn2+ ions in CaCl2 single crystals

In the present investigation the excitation and fluorescence spectra and lifetimes of Mn 2+ ions in calcium chloride, for various manganese concentrations and sample temperatures have been studied for the first time. The fluorescence spectrum consists of an asymmetric broad band, which upon lowering the sample temperature, shifts its maximum from 580 nm at 300 K to 596 nm at 11 K. This luminescence band was associated with the 4 T lg ( 4 G)→ 6 A lg ( 6 S) spin-forbidden transition in the manganese ions occupying Ca-sites in the lattice of CaCl 2 . The excitation spectrum of the Mn 2+ fluorescence revealed the features of manganese ions in octahedral coordination and consisted of nine excitation peaks which were associated with Mn 2+ -crystal-field-sensitive transitions. A crystal field analysis of the wavelength positions of these transitions by means of the model developed by Curie et al. allowed us to determine the magnitude of the cubic field splitting 10Dq, the reduced Racah parameter B', the Koide-Pryce covalency parameter ϵ and the spin transfer coefficients f [sgrave] and f σ . From the measurement of the temperature dependence of the Mn 2+ fluorescence lifetime, we have also obtained information about the different mechanisms which are involved in the relaxation of excited Mn 2+ ions in this host crystal in the temperature range (11-300 K).