Electron-Induced Decomposition of Solid 1,1-Diamino-2,2-dinitroethylene (FOX-7) at Cryogenic Temperatures

Solid FOX-7 (1,1-diamino-2,2-dinitroethylene), an energetic material of interest due to its high stability and low shock/thermal sensitivity, was exposed to energetic electrons at 5 K to explore the fundamental mechanisms leading to decomposition products and provide a better understanding of the reaction pathways involved. As a result of the radiation exposure, infrared spectroscopy revealed carbon dioxide (CO₂) and carbon monoxide (CO) trapped in the FOX-7 matrix, while these compounds along with water (H₂O), nitrogen monoxide (NO), and cyanogen (C₂N₂) were detected exploiting quadrupole mass spectrometry both during irradiation and during the warming phase from 5 to 300 K. Photoionization reflectron time-of-flight mass spectrometry detected small molecules such as ammonia (NH₃), nitrogen monoxide (NO), and nitrogen dioxide (NO₂) as well as more complex molecules up to 96 amu. Potential reaction pathways are presented and assignments are discussed. Among the reaction mechanisms, the importance of an initial nitro-to-nitrite isomerization is highlighted by the observed decomposition products.