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Fluorescence methods for determination of temperature in aerosol particles
Abstract
A hybrid modeling technique has been developed for studying inelastic (fluorescent and Raman) scattering by molecules embedded in spherical particles of large optical size parameters (10$\sp2$ $\sim$ 10$\sp3$). Two shifted (inelastic) emission models have been studied: the unpolarized emission for liquid media and the polarized emission for solid media. The modeling technique uses Lorenz-Mie theory for computing the excitation field inside the sphere. In addition, an inelastic scattering efficiency function is determined using geometrical optics method. The combination of the two methods allows predictions of the angular inelastic scattering patterns and the weighting functions inside the sphere. Results obtained with the hybrid technique are consistent with expected physical behavior and available data in the literature, which were limited to particles of small size parameters ($<$50). The results provide insight into the scattering processes, which can be used to guide experiments and to interpret measurement results. The feasibility of using only one major band in fluorescence spectra for aerosol particle thermometry has been experimentally demonstrated. The experimental work presented includes temperature calibrations of fluorescence spectra for rhodamine B aqueous solutions (5 $\times$ 10$\sp{-6}$ and 1 $\times$ 10$\sp{-4}$mol) and temperature measurements of 52.5 $\mu$m diameter monodispersed droplets of the calibrated solution. Calibration results showed that a potential accuracy of 1 to 1.3$\sp\circ$C could be achieved with the solution system in a temperature range from 20 to 185$\sp\circ$C. Many factors contribute to the experimental error in the optically measured droplet temperature. Primary errors were attributed to the fluctuations in the droplet size, shape and position; the occurrence of optical resonances; and low signal to noise ratios of the fluorescence signals.
Subject Area
Optics|Mechanical engineering|Molecules
Recommended Citation
Zhang, Jingyi, "Fluorescence methods for determination of temperature in aerosol particles" (1991). ETD collection for University of Nebraska-Lincoln. AAI9133322.
https://digitalcommons.unl.edu/dissertations/AAI9133322