Ultrafast high strain rate acoustic wave measurements at high static pressure in a diamond anvil cell

We have used subpicosecond laser pulses to launch ultrahigh strain rate (similar to 10(9) s(-1)) nonlinear acoustic waves into a 4:1 methanol-ethanol pressure medium which has been precompressed in a standard diamond anvil cell. Using ultrafast interferometry, we have characterized acoustic wave propagation into the pressure medium at static compression of up to 24 GPa. We find that the velocity is dependent on the incident laser fluence, demonstrating a nonlinear acoustic response which may result in a shock wave behavior. We compare our results to low strain rate acoustic data. This technique provides controlled access to regions of thermodynamic phase space that is otherwise difficult to obtain. (c) 2008 American Institute of Physics.