OPTICAL SPECTROSCOPY OF MN2-CRYSTALS( IONS IN CACL2 SINGLE)

In the present investigation the excitation and fluorescence spectra a nd lifetimes of Mn2+ ions in calcium chloride, for various manganese c oncentrations 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 58 0 nm at 300 K to 596 nm at 11 K. This luminescence band was associated with the 4T1g(4G) --> 6A1g(6S) spin-forbidden transition in the manga nese ions occupying Ca-sites in the lattice of CaCl2. The excitation s pectrum of the Mn2+ fluorescence revealed the features of manganese io ns in octahedral coordination and consisted of nine excitation peaks w hich were associated with Mn2+-crystal-field-sensitive transitions. A crystal field analysis of the wavelength positions of these transition s by means of the model developed by Curie et al. allowed us to determ ine the magnitude of the cubic field splitting 10Dq, the reduced Racah parameter B', the Koide-Pryce covalency parameter epsilon and the spi n transfer coefficients f(sigma), and f(pi). From the measurement of t he temperature dependence of the Mn2+ fluorescence lifetime, we have a lso obtained information about the different mechanisms which are invo lved in the relaxation of excited Mn2+ ions in this host crystal in th e temperature range (11-300 K).