Probing the evaporation of ternary ethanol–methanol–water droplets by cavity enhanced Raman scattering

Abstract

Cavity enhanced Raman scattering is used to characterise the evolving composition of ternary aerosol droplets containing methanol, ethanol and water during evaporation into a dry nitrogen atmosphere. Measurements made using non-linear stimulated Raman scattering from these ternary alcohol–water droplets allow the in situ determination of the concentration of the two alcohol components with high accuracy. The overlapping spontaneous Raman bands of the two alcohol components, arising from C–H stretching vibrational modes, are spectrally-resolved in stimulated Raman scattering measurements. We also demonstrate that the evaporation measurements are consistent with a quasi-steady state evaporation model, which can be used to interpret the evaporation dynamics occurring at a range of pressures at a particular evaporation time.