Development of a Polarized Raman Spectrometer for Supercritical Fluids Having High Critical Points

概要

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We have developed a specialized instrument for conducting polarization experiments on the vibrational Raman spectra of supercritical fluids under high-temperature, high-pressure conditions. The instrument, consisting of an optical cell and a polarized Raman spectrometer, is designed to accurately measure polarization spectra under difficult conditions, i.e., temperature of 300–700 K and pressure of 0.1–40 MPa. To test the performance of the developed instrument, i) the extinction ratio of the cell’s windows is estimated under high-temperature, high-pressure conditions as well as at room temperature, ii) the polarized and depolarized Raman spectra of standard samples are measured, and iii) the depolarization ratios of the standard samples are evaluated. All of these tests commonly show very good values. Under these conditions, we carry out a polarization experiment on the vibrational Raman spectrum of neat cyclohexane at supercritical states. This is the first time that Raman spectra of supercritical cyclohexane have been measured, as well as the first time that the depolarization ratio of a supercritical fluid has been evaluated as a function of density under high-temperature, high-pressure conditions.
2006-04-15