Ultrafast Shock-Induced Reactions in PETN and RDX Thin Films*

Ultrafast shock interrogation (USI) and ultrafast absorption spectroscopy are used to examine shock compression of PETN and RDX thin films on the picosecond timescale. The USI measurements probe the thermodynamic state (stress and density) of shocked materials interferometrically. At low degrees of compression (V/V₀ > 0.8), the USI data for both materials lie along the unreacted Hugoniots, and agree with previous experimental equation-of-state measurements. At higher degrees of compression (V/V₀ < 0.8), the USI data lie well above the unreacted Hugoniots, with sharp rises near V/V₀ ~ 0.8. These results appear to indicate rapid exothermic reaction of the materials. The temporal evolution of the interferometric signals indicates onset of reaction within ~50 ps after arrival of the shock. Ultrafast optical absorption experiments on shocked RDX support these conclusions.