Metastable changes of the electronic spin-lattice relaxation time in hydrogenated amorphous silicon

Reversible changes in the electronic spin-lattice relaxation time $T_1$ are observed in the case of the dangling-bond defect in hydrogenated amorphous silicon. These changes occur during prolonged illumination with intense light and are completely reversible upon annealing at elevated temperatures in the dark. A possible connection with metastable quenching of localized vibrational modes is discussed.