The document discusses amorphous silicon and the Staebler-Wronski effect. It describes how photoluminescence, electron spin resonance (ESR), and nuclear magnetic resonance (NMR) experiments were used to study the effect of light soaking and annealing on amorphous silicon samples. The experiments showed that light soaking decreased photoluminescence intensity and increased dangling bonds and hydrogen atom movement, while annealing reverted the samples back to their original state.