INVESTIGATION OF COATED DROPLETS IN AN OPTICAL TRAP - RAMAN-SCATTERING, ELASTIC-LIGHT-SCATTERING, AND EVAPORATION CHARACTERISTICS

Single optically levitated microparticles were investigated by Raman s pectroscopy. The particles were composed of di-octyl-phthalate (DOP) a nd glycerol; these substances are not mixable and form a two-phase dro plet. Measurements of the Raman spectrum confirm the formation of drop lets containing both chemical species. The spect;ra show strong input and output structural resonances as expected. If the particle is in re sonance, the field inside the particle is enhanced, and most of the in elastically scattered Light is emitted from molecules dose to the drop let rim. If the particle does not fulfill the resonance condition, the contribution of an individual molecule to the Raman scattering does n ot depend strongly on the radial position of this molecule. On this ba sis, the radial distribution of the two components inside the evaporat ing droplet was determined by time-dependent measurements of the Raman spectrum. Furthermore, elastic-light scattering and the evaporation c haracteristics of the particles were investigated. (C) 1996 Optical So ciety of America