Pressure Dependence of Acoustic Properties in Glycerol by Brillouin Scattering*

Glycerol, a glass-forming fluid, is widely used in research and laboratory settings as a cryoprotectant. We employed high-pressure Brillouin scattering to study the pressure dependencies of longitudinal and transverse acoustic modes of glycerol up to 14 GPa in diamond anvil cells. We observed the transverse acoustic mode which has been unobserved in previous experiments. Our results allow us to derive values for a complete set of elastic properties for glycerol in this pressure range, as well as its density-pressure equation of state. In addition, we performed direct measurements of the pressure-volume equation of state from the sample thickness and area. Our results further allow us to quantify the pressure dependence of γ, the ratio of the adiabatic to the isothermal bulk modulus.