X-ray absorption spectra of explosives for shocked chemical dynamics

Accurate prediction of the reaction of explosives to shocks requires knowledge of the chemical reaction rates that occur as a function of pressure and temperature. Reactive molecular dynamics, both quantum and classical, provide the best current insight into these reaction kinetics. Unfortunately, there are very few experiments that directly measure shock induced chemistry in explosives on time and length scales that allow direct validation of molecular dynamics predictions. This paper reports ultrafast laser driven shock experiments performed at the Linac Coherent Light Source that were designed to look for new observations of shock induced chemistry through changes in the soft X-ray absorption spectra (XAS) at the oxygen K shell edges. Static XAS measurements of explosive films at the carbon, nitrogen, and oxygen K shell edges measured at the Advanced Light Source will also be reported. The motivation for use of XAS is that the near edge structure is sensitive to the local chemical environment, but the broadening due to pressure and temperature is expected to be less problematic than competing chemically specific measurements using vibrational spectroscopies.