Vibronic relaxation processes of the FA center in RbCl:Li

The vibronic relaxation process of FA centers in RbCl:Li, which have Type I emission at low temperatures and Type II emission at high temperatures, has been studied at 10 and 77 K by measuring the resonant secondary radiation (RSR) spectrum from optically excited FA centers with pico-second time-resolved spectroscopy. This study has been prompted by the quest to improve our knowledge on the de-excitation process in the FA centers. The adiabatic potential energy curves are deduced from a theoretical analysis of the measured RSR spectra and compared with those already known. It is shown that Type II relaxation observed at 77 K occurs after Type I relaxation, supporting in turn a model proposed by Baldacchini et al. based on photoluminescence measurements.