Abstract
Noncontact thermometry based on the fluorescence excitation spectrum of aqueous Eu3+(EDTA) near 579 nm allows us to measure the temperature of an evaporating drop of water. The results for drop diameters in the 500-μm–3-mm range confirm theoretical temperature predictions for steady state evaporation. Calibration of the excitation spectrum in a constant temperature cell indicates that ±1.0°C resolution is possible for temperatures below 20°C. The spectrum depends only on the solution temperature when Eu3+(EDTA) concentrations are below 1 × 10−3 M and when the solution pH is between 4.0 and 10.0. Excitation spectra from levitated waterdrops contain additional noise which degrades the temperature resolution to ±1.2°C. With this technique we are able to follow the temperature change in an evaporating drop of water as a monolayer of 1-octadecanol forms on the surface and retards the evaporation.
© 1990 Optical Society of America
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