Ultrafast Nonlinear Optical Investigations of Supercritical Fluids

Abstract

Abstract : During the course of this grant, substantial progress in the investigation of dynamics and intermolecular interactions in supercritical fluids (SCFs) has been made. The project also included studies of liquids to provide understanding of the relationship between SCFs and normal liquids. The research utilized fast (ps) dynamical measurements of solutes in SCFs. The focus has been on experiments that can probe dynamics and interactions on the ground state potential surface. The first measurements of vibrational relaxation of polyatomic solutes in polyatomic SCFs have been made. These measurements are the first to examine dynamics near the SCF critical temperature. Previous bibrational dynamics measurements on systems, such as a diatomic in a rare gas, have been made far from the critical temperature. Measurements, such as fluorescence of large molecules, have also been conducted far from the critical temperature. Our vibrational relaxation experiments are performed using the ps infrared (IR) pump-probe method. As a precursor to future work, we have also made orientational relaxation polarization selective IR measurements in liquids and performed vibrational echo experiments in liquids.