Comparative infrared and Raman spectroscopy of compounds in high-pressure media

The techniques of Fourier transform infrared spectroscopy (FT-IR) and Fourier transform Raman spectroscopy (FT-R) are compared for use in high pressure environments such as those encountered when using supercritical fluid solvents. FT-IR spectra in the 1000 to 3000 cm-1 region show severe pressure broadening of high-pressure molecular solvents, which eliminates much of the useful spectral range when using this technique. These solvent interferences are not a problem with FT-R at pressures as high as 35 MPa. Spectra of naphthalene in liquid carbon dioxide are used to compare these two spectroscopic techniques.