RESONANCE BETWEEN ELECTRONIC AND VIBRONIC LEVELS OF TM3-ALUMINUM-GARNET( IN YTTRIUM)

An attempt to explain some of the Tm3+ spectra features in YAG in term s of the splitting of the zero-photon lines due to the even part of th e linear vibronic interaction Hamiltonian with a single active phonon mode in the cases of resonance or quasi-resonance between a pure elect ronic and vibronic level is presented. The observed features in absorp tion and emission spectra are discussed and the active mode is identif ied. The experimental splittings and intensities allow estimation of t he vibronic coupling matrix elements of about 4-5 cm(-1).