Ultrafast reaction dynamics of nitro-organic molecular cations

Shock initiation of energetic materials produces cations and anions that contribute to the chemical reactions leading to detonation. Despite their potential importance, these transient charged species are difficult to detect in detonation experiments and often ignored in molecular dynamics modeling of shocked energetic materials. The pump-probe technique of femtosecond time-resolved mass spectrometry (FTRMS) and complementary quantum chemistry calculations can unravel initial unimolecular dissociation reactions of transient cationic species on femtosecond-picosecond timescales. This presentation will discuss insights gained into sub-picosecond reaction timescales of ionized energetic molecules including nitro-nitrite rearrangement in nitromethane cation, Coulomb explosion of multiply charged nitrotoluene cations, and direct dissociation of the metastable ethylene glycol dinitrate (EGDN) cation. The potential use of FTRMS measurements and calculations to inform design of laser-initiated energetic materials and advance explosive detection applications will also be discussed.