Detection of Water Droplet Size and Anion Species by Nonlinear Optical Scattering

摘要

The liquid-air interface causes the droplet to act as an optical cavity which provides large internal fields and feedback. The stimulated Raman scattering (SRS) spectra of micrometer-size water droplets containing different anions (e.g., nitrate, sulfate, and phosphate can be generated by a single laser pulse and detected by an optical multichannel analyzer. When the spontaneous Raman intensity of the V1 mode of the anions is larger than that of the O-H stretching mode of water, the SRS spectra consist of the peak at V1 and multiple peaks of nearly equal wavelength separation within the O-H stretching mode of water. These multiple peaks are associated with the morphology-dependent resonances of a sphere and the refractive index of water. Keywords: Spontaneous Raman scattering, Raman scattering, Micrometer size droplets, High intensity, Laser, Interaction, Droplets, Morphology, Resonances, Water, Heavy water.