Microdroplet missing-resonance spectroscopy

摘要

Abstract: an be trapped inside droplets by total internal reflection, and resonant conditions are known to exist for particular values of the radiation wavelength, droplet size, and refractive index. Such resonances have been observed previously in fluorescence from dye-doped droplets, and their presence or absence is controlled by the amount of droplet absorption at the resonance wavelength. These resonance peaks can be regarded as very sensitive absorption indicators, providing both quantitative and spectral information. Recent efforts have shown that the relative strength of resonance peaks in fluorescent emission can be modeled to give excellent agreement with known concentrations of rhodamine dye dissolved in ethanol droplets both for self- absorption and for absorption due to nigrosin additive, with sensitivities approaching 0.001 cm$+$MIN@1$/. Using the model developed from these experiments, additional work with bromo- cresol green dye additives shows diagnostic application of the 'missing resonance spectroscopy' could provide new experimental information as a droplet concentration or pH sensor.!16