RDX- and HMX-Related Anionic Species Explored by Photoelectron Spectroscopy and Density Functional Theory

Abstract

Anion photoelectron spectroscopy, supported by density functional theory (DFT) calculations, is employed to study energetic materials RDX (3,5-trinitroperhydro-1,3,5-triazine) and HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). Their isolated anions and decomposition products are generated by matrix-assisted laser desorption ionization (MALDI). Their anionic parent species are not observed, but instead accessible fragmentation ions are detected. The vertical detachment energies (VDEs) of these anionic, dissociation-generated species are experimentally determined, and the corresponding structures are identified by comparing DFT-calculated VDEs to the experimental ones. RDX– and HMX– can fragmentate through the loss of HNO2, NO2, and NCH2 groups. RDX– loses up to two NO2 groups and one NCH2 moiety, and HMX– can fragment by up to three NO2 groups and two NCH2 moieties. The mass units of (RDX – H – NO2)−, (RDX – H – (NO2)2)−, and (RDX – NCH2 – (NO2)2)− are the same as those of (HMX – H – (NO2)2 – NCH2...