Photo and Electrical Field Effects in Energetic Materials

The relationship between the pseudostability of explosives and their electronic structure has been identified and discussed. Specifically, direct, non-thermal, photoelectric initiation of certain energetic materials was shown to occur upon simultaneous application of an electric field and light of an appropriate wavelength. To further characterize the microscopic processes responsible for photoelectronic initiation, it is necessary to study in detail the photodecomoisition produced by light with no electric field, and to study the initiation by electric fields in the absence of light with particular emphasis on electrode effects. The authors report here new experimental results which elucidate the mechanism of photoelectronic initiation in lead azide. The spectral and intensity dependence of photodecomposition was monitored by observing the release of nitrogen gas from the azide sub-lattice. Decomposition of the lead sub-lattice was observed by the change in optical density due to formation of colloidal lead. Threshold electric fields have been established for selected metal contacts. A model of the photoelectronic process in lead azide is proposed which takes into account new results from studies of photodecomposition and electric field effects and previous work on photoconductivity and optical absorption.