Dissociative Electron Attachment to the Nitroamine HMX (Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine)

TL;DR

This study investigates how electrons attach and cause dissociation in HMX, revealing specific fragment ions, their formation energies, and differences from related explosives, highlighting HMX's high sensitivity and complex reaction pathways.

Contribution

First detailed DEA measurements on gas-phase HMX, identifying key fragment ions and their formation energies, and distinguishing HMX from RDX via negative ion mass spectrometry.

Findings

Identified dominant fragment ions at 46u and 176u.

Observed low-energy electron attachment leading to complex bond cleavages.

Differentiated HMX from RDX based on resonance intensity ratios.

Abstract

In the present study, dissociative electron attachment (DEA) measurements with gas phase HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, $C_4H_8N_8O_8$, have been performed by means of a crossed electron-molecular beam experiment. The most intense signals are observed at 46 and 176u and assigned to $NO_{2}^{-}$ and $C_3H_6N_5O_{4}^{-}$, respectively. Anion efficiency curves for 15 negatively charged fragments have been measured in the electron energy region from about 0-20 eV with an energy resolution of ~0.7 eV. Product anions are observed mainly in the low energy region, near 0 eV, arising from surprisingly complex reactions associated with multiple bond cleavages and structural and electronic rearrangement. The remarkable instability of HMX towards electron attachment with virtually zero kinetic energy reflects the highly explosive nature of this compound. Substantially different intensity ratios of resonances for common fragment anions allow distinguishing the nitroamines HMX and royal demolition explosive molecule (RDX) in negative ion mass spectrometry based on free electron capture.