Transcript PFBAm.pptx
1 Comparison of Experimental and Theoretical Cross-sections of PFBAm By: Paul J. Godin, Stephanie Conway, Angela Hong, Karine Le Bris, Scott Mabury, and Kimberly Strong. 68th International Symposium on Molecular Spectroscopy 2 Outline • • • • • • Motivation Experimental Apparatus Theoretical Calculations Preliminary Results Future Work Conclusions 3 Motivation • Perfluroalkyl amines (PFAm) are stable liquids commonly used in electronic testing and as heat transfer agents. Evaporation results in atmospheric concentrations. • PFAms have long atmospheric lifetimes due to no known sinks (~500 yrs). • C-F bond absorbs strongly in the atmospheric window (750-1250 cm-1). • Thought to be potential greenhouse gases due to high radiative efficiencies. 4 Motivation • The goal of our study is temperature dependent measurements of perfluorotributylamine (PFBAm). • Previous room temperature measurements have been done with a resolution of 0.25 cm-1 (Young et al., 2010). • The presence of the congener has not been taken into account in previous measurements. PFBAm Congener 5 Atmospheric Measurements • In situ measurements of PFBAm in March 2012 at Toronto. • Back trajectories calculated using NOAA HYSPLIT program. 6 Experimental Set-up 7 Theoretical Calculations • Low level geometry optimization calculation followed by high level frequency calculation. • PBFAm: Gaussian B3LYP/6-311G(d,p). • Congener: Gaussian B3LYP/6-311++G(3df,3pd). • Standard pressure and temperature. 8 Theoretical Calculations 9 Preliminary Measurements Offset by 0.5x10-17 10 Preliminary Measurements • Presented absorption cross-section is a scaled average of different pressures recorded ranging from 2-4 Torr. • No correction yet made for MCT detector nonlinearity. • Results appear to suggest that sample contains very little of the congener. • Presently optimizing experimental set-up for PFBAm measurements. 11 Facility Improvements • Currently building a new coolable multi-pass White Cell with optical path greater than 50 m. • Designed for low pressures (1 atm max). • Tentative list of molecules: CH4, H2O, and CO2. • CO2 pressure broadening coefficients. 12 Conclusions • Initial lab measurements of PFBAm have been recorded at room temperature. • Theoretical calculations of PFBAm and congener have been performed using Gaussian B3LYP/6311G(d,p) and B3LYP/6-311++G(3df,3pd) respectively. • Working on improvements to small cell to enable acquisition of a comprehensive set of temperaturedependent cross section measurements. • Long-path cell in development for measurements of weakly absorbing molecules.