A number of wide bandgap inorganic materials can be prepared so that stimulation with nanosecond pulses of near infra-red (1064 nm-Nd:YAG fundamental) generates intense, transient white light. This light can span from 300 to 900 nm. Here, we characterize this emission from single crystal NaNO3 and show that it is due to optical breakdown in the bulk. We contrast the behavior and character of time resolved spectra of this bulk breakdown with surface breakdown and provide evidence of defect mediated processes being responsible for the observed avalanche. We also conclude that confinement of the avalanche is essential for the production of this broad banded luminescence. (C) 2002 Elsevier Science B.V. All rights reserved.