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Advanced Stimulated Scattering Measurements in Supercritical Fluids
Final rept. 1 Feb-31 Oct 2001
SRI INTERNATIONAL MENLO PARK CA
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Stimulated Brillouin and Rayleigh scattering was applied to measurements of supercritical fluids. Measurements were performed using an injection-locked NdYAG laser as a pump laser and an external cavity diode laser as a probe laser. Improvements were made in stability of the probe laser, allowing more reliable operation and in the stability of the pump laser, allowing narrower bandwidth operation. Improvements were made to a supercritical cell to allow measurements in the near critical region Software was written to enable automated analysis of measured spectra to extract the widths, shifts, and heights of the electrostrictive Brillouin, thermal Brillouin, and thermal Rayleigh peaks. Comparison of these features with theory has showed consistency of the theory through the relationships between the heights and widths of the thermal Brillouin and thermal Rayleigh peaks. Elastic and thermal properties extracted from the measurements agree with literature values for room temperature and atmospheric pressure conditions. Brillouin and Rayleigh measurements were performed over a wide range of supercritical and near-critical conditions. Interesting, unexpected structure in the behavior of the Brillouin shifts, width, and heights was observed in the supercritical region.
APPROVED FOR PUBLIC RELEASE