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

► The index of refraction was derived to near 50 GPa using Infrared reflectivity. ► The sample thickness was derived and the resulting data was fit to an EOS. ► The molecular to polymeric transition has been correlated to the appearance of two bands in the IR. ► Comparisons were made between the data herein and existing X-ray and shock data.