Untangling the Reaction Mechanisms Involved in the Decomposition of Nitramine-Based Energetic Materials in the Condensed Phase
Abstract
The primary objectives of this project are to explore experimentally the mechanisms involved in the decomposition of key representatives of nitramine-based energetic materials (RRNÐNO2; RDX, HMX, CL-20) in the condensed phase (solid state) and to identify the primary and higher order reaction products, among them carbon-, nitrogen-, and oxygen-centered radicals, which are formed in these processes. This presents a major experimental challenge since no comprehensive study has been conducted to date, in which the decomposition mechanisms of nitramine-based energetic materials and the overall spectrum of newly formed open and closed shell products have been explored on line and in situ in the condensed phase. These data are very much required by the energetic material community to unravel the mechanisms and bond breaking processes, which trigger the decomposition of energetic molecules and Ôswitch onÕ the supply of radicals in the decomposition. These objectives are achieved by systematically initiating the decomposition of the nitramines in the condensed phase by ÔpumpingÕ energy into these molecules via infrared multiphoton dissociation (IRMPD) and single photon ultraviolet photodissociation (UVPD) while tracing the products formed in these processes in an ultra-high vacuum machine. Our experimental setup incorporates highly complementary detection schemes to monitor these processes on line and in situ within the solid state (Fourier Transform Infrared (FTIR), Raman, ultraviolet-visible (UVVIS) spectroscopy) and by detecting the products subliming into the gas phase via single vacuum ultraviolet (VUV) photon soft ionization (PI) followed by a mass spectroscopic analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF-MS) to reveal the complex dissociation processes of nitramine-based energetic materials comprehensively. By initiating the decomposition of three key representatives of nitramine-based energetic materials via IRMPD and UVPD and following the formation of new molecules on line and in situ, we extract versatile concepts on the reaction mechanisms, products and their branching ratios, and intermediates in the decomposition of nitramine-based energetic materials. Besides the basic scientific interest from the energetic materials community, these studies are also of fundamental interest to the physical (organic) chemistry community to unravel fundamental decomposition mechanisms of complex organic molecules, to probe isomerization processes of organic transient species on electronic ground and excited state surfaces, and to correlate distinct fragmentation mechanisms with the molecular structure of the molecule thus ultimately providing a systematic understanding and key concepts of the decomposition of nitramine-based energetic materials in the condensed phase.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810438
Entities
People
- Ralf I Kaiser
Organizations
- Army Contracting Command
- Office of the Secretary of Defense
- University of Hawaiʻi System