High pressure refractive index measurements of 4:1 methanol:ethanol

Abstract

A new technique for measuring the refractive index at high pressure in a diamond anvil cell is reported. This technique was applied to a 4:1 methanol:ethanol mixture at room temperature and pressures up to 16.9 GPa. A parameterization is given for the refractive index that fits the data with a residual standard error of 4×10−3 at frequencies between 12 000 and 24 000 cm−1 and pressures between 0.5 and 11.5 GPa. A sharp change in slope of the refractive index vs pressure was observed at the glass transition near 10 GPa. Modifications of the technique which should allow measurements of the refractive index to much higher pressures are discussed.