Effects of resonant electron-phonon interactions for RE3+ ions in laser crystals

This paper presents a theoretical treatment of electron-phonon interaction problem in the case of quasi resonant interaction for rare earths ions in laser crystals. Expressions for the absorption or emission lineshapes (asymmetries or splittings of zero-phonon lines) are obtained. The theory is applied to explain some spectral features of Yb 3+ transitions in YAG; it allows also the estimation of the vibronic coupling strengths, phonon energies and the `unsplit' electronic levels. A new electronic energy level scheme of Yb 3+ in YAG is proposed.