Derivation of the isothermal equation of state of carbon monoxide to 50 GPa

The refractive index of carbon monoxide was derived to near 50 GPa using Infrared reflectivity. Variances in the refractive index near 5.5 GPa were related to a previously identified phase transition. A combination of refractive index and image mapping permitted extraction of the sample thickness as a function of pressure, which when fit with a third-order Birch–Murnaghan EOS, revealed the pressure–volume relationship is in good agreement with X-ray diffraction and a computationally predicted shock Hugoniot of non-reactive carbon monoxide over a limited pressure range.