Surface acoustic waves in the diamond anvil cell: An application of impulsive stimulated light scattering

Impulsive stimulated light scattering (ISS) has been used to probe the pressure dependence of the surface acoustic waves supported at the interfaces formed by single crystals of Ge and Ta in contact with the pressure-transmitting media liquid methanol and solid Ar, respectively. In the former system, the relevant excitation is a Scholte wave; its velocity has been measured as function of direction in the crystal surface to a pressure of 2.2 GPa. In the latter system, the velocity of the Stoneley wave has been measured in the same way to a pressure of 7.7 GPa. In both cases, calculated velocities, obtained by evaluating the surface perpendicular elastodynamic Green's function, agree closely with measured velocities. When combined with additional information, such as the bulk modulus, these type of measurements provide a means to precisely determine the high pressure behavior of the individual elastic constants of opaque materials.