Internal Vibronics in Terbium Compounds—A Cooperative Phenomenon

The observation of absorption and emission vibronics in Tb3+ compounds is reported. This follows a similar analysis of Gd3+ compounds and a comparison is made between the two cases. A theoretical model based on a cooperative approach to these transitions is developed. This model yields the activity of vibrational modes involved in internal vibronics. It also gives the relative intensity of a vibronic compared to its parent electronic transition as a function of the particular rare-earth (RE) ion and of its physical surroundings.