Thermodynamic properties of liquid gallium from picosecond acoustic velocity measurements.

Due to discrepancies in the literature data the thermodynamic properties of liquid gallium are still in debate. Accurate measurements of adiabatic sound velocities as a function of pressure and temperature have been obtained by the combination of laser picosecond acoustics and surface imaging on sample loaded in diamond anvil cell. From these results the thermodynamic parameters of gallium have been extracted by a numerical procedure up to 10 GPa and 570 K.

Equation of state of liquid mercury to 520 K and 7 GPa from acoustic velocity measurements.

Ultrafast acoustics measurements on liquid mercury have been performed at high pressure and temperature in a diamond anvil cell using picosecond acoustic interferometry. We extract the density of mercury from adiabatic sound velocities using a numerical iterative procedure. We also report the pressure and temperature dependence of the thermal expansion, isothermal and adiabatic compressibility, bulk modulus, and pressure derivative of the latter up to 7 GPa and 520 K.

Picosecond acoustics method for measuring the thermodynamical properties of solids and liquids at high pressure and high temperature.

Based on the original combination of picosecond acoustics and diamond anvils cell, recent improvements to accurately measure hypersonic sound velocities of liquids and solids under extreme conditions are described. To illustrate the capability of this technique, results are given on the pressure and temperature dependence of acoustic properties for three prototypical cases: polycrystal (iron), single-crystal (silicon) and liquid (mercury) samples. It is shown that such technique also enables the determination of the density as a function of pressure for liquids, of the complete set of elastic constants for single crystals, and of the melting curve for any kind of material.

Ultrafast acoustics in the middle UV range: coherent phonons at higher frequencies and in smaller objects.

We show that the propagation of coherent acoustic phonons generated by femtosecond optical excitation can be clearly resolved using a probe laser in the middle UV (MUV) range. The MUV probe is easily produced from a high-repetition-rate femtosecond laser and a homemade frequency tripler. We present various experimental results that demonstrate efficient and high frequency detection of acoustic phonons.

Scaling the temperature-dependent boson peak of vitreous silica with the high-frequency bulk modulus derived from Brillouin scattering data.

The position and strength of the boson peak in silica glass vary considerably with temperature T. Such variations cannot be explained solely with changes in the Debye energy. New Brillouin-scattering measurements are presented which allow determining the T dependence of unrelaxed acoustic velocities.