Radial profiling of microdroplets using cavity-enhanced Raman spectroscopy

The composition of 7.7-microm-radius methanol-water droplets was radially resolved by cavity-enhanced Raman spectroscopy. Optical cavity modes, encompassing well-defined radial zones within each droplet, were sequentially excited by a 514.5-nm laser beam to generate spontaneous Raman scattered light. The cavity-enhanced Raman spectral peaks gave information as to the identity and amount of species present. The measured radial and time dependence of the methanol concentration agreed with a diffusion-limited evaporation mode.