Laser-induced shape distortions of flowing droplets deduced from morphology-dependent resonances in fluorescence spectra

Abstract

Low-energy laser irradiation (∼0.15 μJ) on a Rhodamine 6G ethanol droplet (radius, 21.1 μm) flowing in a linear stream has been shown to induce damped oscillations in the wavelengths at which the morphology-dependent resonances (MDR's) in the fluorescence are located. Such oscillatory behavior of the MDR's is consistent with those calculated for the elastic scattering from a large sphere that oscillates with small amplitudes (5 parts in 10⁴) from a sphere to a prolate spheroid and then to an oblate spheroid. The observed damped oscillations provide information on the surface tension and viscosity of an ethanol droplet.