Analytical Chemistry Seminar: Melissa Ugelow
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
Optical Properties of Titan Haze Analogs Using Photoacoustic and Cavity Ring-Down Spectroscopy
Melissa S. Ugelow 3rd Year Graduate Student
The organic haze that surrounds Saturn's moon Titan is formed through the photolysis and electron initiated dissociation of methane and nitrogen. Both the chemical pathways leading to the haze formation and the resulting haze optical properties are still highly uncertain. Here we examine the optical properties of simulated haze aerosol to better understand its scattering and absorption properties, and the impact of haze on Titan's radiative balance. To determine the complex refractive index of haze particles, we combine two spectroscopic techniques, one that measures absorption and one that measures extinction: photoacoustic spectroscopy coupled with cavity ring-down spectroscopy (PASCaRD). This technique provides the benefit of a high precision determination of the imaginary component of the refractive index (k), along with the highly sensitive determination of the real component of the refractive index (n) in a flow system set up. The Titan aerosol analogs studied are produced by two energy sources, UV excitation and spark discharge excitation. The refractive indices are determined at two wavelengths, 405 and 532 nm, using the PASCaRD system. I will present preliminary data on the complex refractive indices of laboratory generated Titan aerosol analogs at both wavelengths using both energy sources. The high precision values determined from this method should be useful for modelers and for data retrieval from spacecraft and remote sensing instruments.