Infrared multiphoton dissociation of RDX in a molecular beam

Abstract

Infrared multiphoton dissociation (IRMPD) of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a molecular beam has been performed in order to investigate the mechanism of RDX thermal decomposition. A beam of molecules was crossed by a pulsed TEA CO2 laser and velocity distributions of the various products were measured by the time-of-flight (TOF) technique as a function of the laboratory angle using a mass spectrometric detector. The dissociation channels, their branching ratios, and the translational energy distributions of the products were determined. In contrast to the conventional view of simple bond rupture through loss of NO2 as the dominant primary channel in RDX decomposition, it was found that the dominant primary channel is concerted symmetric triple fission to produce three CH2N2O2 fragments which subsequently undergo secondary concerted dissociation to produce HCN, H2CO, HONO (or HNO2), and N2O. A total of two primary and four secondary dissociation channels were observed. Concerted reactions predominate over simple bond rupture not only in the number of channels (four vs two) but also in the amount of products. A fair amount of translational energy release through concerted reaction channels was observed, which is significant for an explanation of the energies of RDX decomposition.

Molecular beam studies of the photodissociation of benzene at 193 and 248 nm

“…can be used to elucidate the neutral reaction pathways in photodissociation and has been successfully applied in a series of studies of the concerted decomposition of cyclic organic [16][17][18] molecules.…”

A Comparative Study of the Reaction Dynamics of a Model System Using Different Criteria in Parameterizing the Potential Energy Function

“…Although there are experimental evidence (Zhao, Hintsa, and Lee 1988) and theoretical predictions (Mowrey et. al 1990) that unimolecular decay of CH 2 NNO 2 is more likely to occur by concerted dissociation pathways than through N-N bond scission, for our purposes our models only describe bond scission reactions.…”

97/03053 Infrared fiber-optic diagnostic observations of solid propellant combustion

“…We can add the comment that the nature of the initiating process for RDX thermal decomposition has been particularly controversial because of a seeming disagreement between the above-mentioned results of infrared multiphoton dissociation experiments by Zhao et al 32 showing that two-thirds of their RDX decomposed by a concerted detrimerization process. and the condensed phase experiments which find little or no evidence for such a process.…”