High resolution FTIR spectroscopy of BaY2F8 single crystals doped with trivalent Er

High resolution (0.04 cm(-1)) FTIR spectroscopy is applied to monoclinic Er3+-doped BaY2F8 single crystals in the wavenumber range 500-24000 cm(-1) and temperature range 9-300 K to study the crystal field splitting of the fundamental I-4(15/2) and of the excited I-4(13/2), I-4(11/2), I-4(9/2), F-4(9/2), S-4(3/2), H-2(11/2), F-4(7/2), F-4(5/2), and F-4(3/2) states and the effects caused by increasing Er3+- concentrations (2-20% m.f), such as inhomogeneous line-broadening and new lines due to Er3+-Er3+ interaction. In the framework of the electron-phonon interaction, the thermally induced line-broadening and -shift are detected and accounted for by the two-phonon Raman model and the vibronic replicas of a few lines are investigated.