Shock-driven chemistry and reactive wave dynamics in liquid benzene

Benzene (C6H6) is a stable molecule because of its electronic structure - aromatic stability is derived from its delocalized, pi-bonded, 6-membered planar ring structure. Under extreme P,T conditions benzene has been shown to be chemically reactive. Benzene principal shock Hugoniot states have been reported previously by several groups, at both high and low pressures. Cusps (or discontinuities) in the shock Hugoniot provide evidence that chemical reactions take place under shockwave compression of benzene at input pressure conditions above 13 GPa. In other shock-driven experiments, spectral changes have been observed in benzene near this cusp condition, indicating that the cusp is associated with shock-driven chemical reaction(s). In this work, a series of gas-gun-driven plate impact experiments were performed to measure and quantify the details associated with shock-driven reactive flow in benzene. Using embedded electromagnetic gauges (with up to 10 Lagrangian gauge positions in-material in a single experiment) multiple, evolving wave structures have been measured in benzene when the inputs were above 13 GPa, with the details changing as the input pressure was increased. Detailed insights into the volume changes associated with the chemical reaction(s), reaction rates, and estimates of the bulk moduli of reaction intermediates and products were obtained from the mutiple wave structures and their evolution. Using this new experimental data (along with the older experimental data from others), the benzene reactant and product Hugoniot loci have been modeled by thermodynamically complete equations of state (EOS).