<i>Probing Intermediate Formation of Thin Film Explosives Through Ultrafast Broadband Infrared Spectroscopy</i>

A first step to predicting explosive performance and safety is to understand the chemical pathways taken when high explosive materials are shocked. Unfortunately, there is insufficient data at relevant time and length scales to directly compare experiments to molecular level models. The intention of this work is to link experimental results to molecular dynamics models using ultrafast broadband mid-infrared and visible absorption spectroscopy to probe the chemical changes energetic materials undergo when shocked. PETN, a common HE, was shocked to the reactive regime and showed increased absorption near the anti-symmetric NO₂ stretch but not the symmetric NO₂ stretch. This change was attributed to absorbance from intermediate formation. These results were compared to molecular dynamics and accelerated chemistry models to interpret the shock chemistry. Comparing to gas phase calculations of the infrared absorption intensities, the intermediate was most likely HONO indicating H-ion and NO₂ elimination play an important role in early shock chemistry for PETN.