Electronic and vibrational levels of the photochromic Mn in sillenites

Visible and high resolution FTIR spectroscopy (at 9 K) and MCD (at 1.4 K) m easurements are applied to study the valency and the coordination of Mn in photorefractive and photochromic sillenites (BSO BGO, BTO and mixed BSO-BMn O) single crystals. Vibrational transitions of Mn5+ in T-d symmetry, due to excitation of an F mode, its overtone and combination with an A mode are d etected. The crystal field spectra and MCD results strongly support the d(2 ) configuration for Mn in T-d symmetry. Vibronic replicas of the (3)A(2) -- > E-1 electronic transition, In which ones or two vibrational modes are als o excited, are reported.