Colloquium

Upcoming Colloquium

Determining the Radiative Properties of Anthropogenic Halocarbons by Integrating Experimental FTIR Spectroscopy with Quantum Chemistry Calculations
Dr. Karine Le Bris, CSU Los Angeles

October 12, 2026
11:00am-12:00pm in HSCI-102

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Anthropogenic halocarbons are molecules widely used as refrigerants, propellants, repellents, pharmaceuticals, and pesticides. Many persist in the atmosphere, where they influence climate by absorbing terrestrial infrared radiation. Quantifying these effects requires characterization of their mid-infrared radiative properties. The first part of this talk discusses the acquisition of infrared spectra using Fourier-transform infrared (FTIR) spectroscopy. Absorption cross sections measured under controlled conditions quantify the molecular interactions with terrestrial radiation. The second part examines how quantum-chemical calculations complement these measurements. Calculated vibrational frequencies and infrared intensities support band assignments and extend spectral coverage beyond the instrumental range. Combining measured and calculated spectra enables estimates of the molecule’s atmospheric radiative efficiency. Calculated reaction rate coefficients with OH also provide estimates of tropospheric lifetimes. Because global warming potential depends on both radiative efficiency and atmospheric lifetime, integrating these experimental and computational approaches provides a more comprehensive and robust framework for assessing the climate effects of halocarbons.

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