Polarization Measurements on Raman Scattering from Spherical Droplets

The polarization of Raman scattering from a single spherical droplet has been measured for the first time. Experiments are performed in a quadrupole cell, in which a charged liquid droplet is trapped by electro-dynamic forces. Raman scattering intensities at the 90° angle are measured for polarizations both parallel and perpendicular to that of the incident beam. The depolarization ratios thus obtained for the droplets are shown to be identical to those measured in the bulk samples. The present results indicate unequivocally that the depolarization ratio of Raman scattering is a molecular property and, as such, is not affected by the boundary conditions of the spherical droplets. Subsequently, the technique is applied to the chemical characterization of solution droplets. The presence of ion pairs in supersaturated strontium nitrate and bisulfate solutions is dramatically verified by distinct changes in the depolarization ratios.