A vacuum ultraviolet photoionization study on the isomerization, decomposition, and molecular mass growth processes in solid nitromethane (CH3NO2)

In this Feature Article, we highlight the crucial findings from experimental and theoretical studies investigating the dissociation mechanisms of condensed phase nitromethane (CH3NO2), a model compound of nitrohydrocarbon (R-NO2) based energetic material. Our findings on intriguing isomerization, decomposition and molecular mass growth pathways of nitromethane are placed into perspective by exploiting complementary spectroscopy probes such as Fourier Transform Infrared Spectroscopy (FTIR), Electron Paramagnetic Resonance (EPR), and single-photon isomer selective photoionization reflectron time-of-flight mass spectrometry (PI-ReTOE-MS) in conjunction with quantum chemical calculations. These investigations unravel the isomerization of nitmmethane to exotic isomers such as aci-nitromethane, nitrosomethanol, and N-hydroxyoxaziridine. Evidence of non-equilibrium decomposition channels involving suprathermal oxygen, hydrogen and carbene formation are also revealed. Finally, involvement of these radical species in molecular mass growth processes leading to higher molecular weight products are emphasized. Benchmark studies established from a 'simple' nitromethane system are highly beneficial to predict the decomposition mechanisms of 'real' explosives.

Automated summary

This Feature Article highlights the dissociation mechanisms of condensed phase nitromethane, emphasizing isomerization, decomposition, and molecular mass growth pathways, as well as non-equilibrium decomposition channels involving radical species. Benchmark studies on nitromethane system are beneficial for predicting the decomposition mechanisms of real explosives.