Experimental methods were developed to obtain single-shot, photoacoustic measurements in shock compressed thin samples. Impulsive stimulated thermal scattering measurements were used to measure acoustic velocities normal to the shock propagation direction in liquid benzene compressed to nearly . Although the resulting pressure-temperature states correspond to the solid region of the benzene phase diagram, shocked benzene remains a liquid at pressures well above the static compression threshold for freezing. Photoacoustic measurements provide a useful approach to examine structural changes in shocked materials.
For the liquid phase, the longitudinal acoustic wave speed is determined by the bulk modulus, resulting in a lower wave speed compared to the solid phase.