Time-resolved emission spectroscopy of nitramine and hydrogen-free explosives under shock loading

Understanding the early chemical reactions during growth to detonation is critical to the development of robust detonation theories and non-phenomenological models. While early chemical steps, including transfer of energy through molecular and lattice vibrations and breaking of the first chemical bonds, occur over femtoseconds to picoseconds, subsequent reactions involving small-molecule intermediates can occur over nanoseconds. As part of an effort to provide a description of early chemistry in explosives across multiple time and length scales, we have performed streak emission spectroscopy experiments with nanosecond time resolution, comparing the behavior of typical nitramine and hydrogen-free explosives during growth to detonation. These experiments utilize Sandia's High Throughput Initiation platform, using laser-driven flyer plates to rapidly investigate multiple sample geometries and flyer impact velocities. Initial results with cyclotrimethylene trinitramine (RDX) show a clear evolution of spectral signature with time following impact at specific flyer velocities. These results will be discussed in the context of concurrent simulation efforts and vibrational energy transfer experiments at femtosecond to picosecond timescales.