comparison of experimental and theoretical cross-sections of pfbam by: paul j. godin, stephanie...

1

Comparison of Experimental and Theoretical Cross-sections of PFBAmBy: 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.CongenerPFBAm

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 non-linearity.

•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/6-311G(d,p) and B3LYP/6-311++G(3df,3pd) respectively.

• Working on improvements to small cell to enable acquisition of a comprehensive set of temperature-dependent cross section measurements.

• Long-path cell in development for measurements of weakly absorbing molecules.