Optical measurements of electrodynamically levitated microparticles

E. James Davis

doi:10.1117/12.44246

1 July 1991 Optical measurements of electrodynamically levitated microparticles

E. James Davis

Proceedings Volume 1435, Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications; (1991) https://doi.org/10.1117/12.44246
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

Development of the electrodynamic balance with laser light-scattering capabilities has made it possible to perform a wide variety of measurements on solid particles and liquid droplets with sizes ranging from about 0.1 to 200 micrometers and masses in the range 10-15-10-5 g. An introduction to the principles and design of electrodynamic balances is provided, and recent advances in their application to the measurement of optical properties, chemical composition and chemical reaction rates via elastic and inelastic scattering from microparticles are reviewed. Of particular emphasis are the phenomena of morphological or structural resonances, which can be used to determine optical properties of dielectric spheres with very high precision, and Raman and fluorescence spectroscopies, which provide information on the chemical nature of the microparticle. It is demonstrated that elastic and inelastic scattering measurements on levitated microdroplets can be used to measure chemical composition changes of multicomponent droplets. It is also shown that the complex refractive index of weakly absorbing droplets can be determined by measuring their evaporation rates via optical resonance spectra. The major problem associated with the interpretation of Raman spectra for microparticles is examined, and that is the effect of morphological resonances on the Raman emission. Data on the enhancement of Raman signals by such resonances are presented.

Citation Download Citation

E. James Davis "Optical measurements of electrodynamically levitated microparticles", Proc. SPIE 1435, Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications, (1 July 1991); https://doi.org/10.1117/12.44246

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