Abstract

Elastic and Raman scattering data from single homogeneous or layered microdroplets suspended in an electrodynamic balance have been obtained by scanning a tunable ring dye laser, Wavelengths of transverse magnetic (TM) and transverse electric (TE) mode resonances in light scattered elastically by a droplet have been measured independently by using two detectors in the planes parallel and perpendicular to the plane of polarization. Simultaneously, Raman scattered light at a fixed wavenumber shift has been measured. Using an alignment procedure, differences between the observed and theoretical positions of TE and TM mode resonances are minimized to obtain size and wavelength-dependent refractive index of homogeneous and layer droplet. The procedure permits absolute size and refractive index determination with relative errors of 3 x 10^-5, and detection of a monolayer on a droplet. The size and refractive index data are used to analyze observed resonances in Raman scattering. Results show that all resonances having theoretical FWHM less than 1.0 x 10^-4 cm^-1 appear in Raman spectra. Even though theoretical widths of the resonances observed in Raman spectra are extremely narrow, experimental peaks are found to have widths no less than 0.20 cm^-1. The observed peak broadening and heights can not be explained by absorption but suggests an oscillation of droplet size by about 5 A.

© 1993 Optical Society of America