Pacific Northwest National Laboratory The Ohio State University 20 June 2006 T. Masiello, T.J. Johnson and S.W. Sharpe Pacific Northwest National Laboratory Richland, Washington Quantitative IR Spectra and Vibrational Assignments of CH 2 I 2, an Atmospheric Aerosol Precursor

Pacific Northwest National Laboratory The NWIR Infrared Library  Designed for Remote Sensing: P-broadened to 760 Torr (N 2 )  Spectral resolution (0.1 cm -1 ) is suitable for both active and passive sensors, pressure broadened limit  Chemical content focused on DOE needs  Existing IR spectral libraries are rarely quantitative (exceptions: HITRAN, GEISA), and lack QA-QC data  NWIR currently ~450 Molecules  Ever-expanding Library

Pacific Northwest National Laboratory The NWIR Infrared Library  PRESSURE: 760 ± 5 Torr  RANGE:  600 cm -1 to  6500 cm -1  TEMPERATURES:(5), 25, 50 o C  NOISE LEVEL:  5 x OD at 10  m  DATA FORMAT:.txt and.spc format, 1 ppm-m  NOTES:Export restricted from sensitive countries

Pacific Northwest National Laboratory Motivation- Why CH 2 I 2 ? Jimenez, J. L. et al. (2003), J. Geophys. Res., 108(D10), 4318

Pacific Northwest National Laboratory 90 o Polarized 0 o Polarized Polarized FT-Raman Spectrum 1064 nm Excitation

Pacific Northwest National Laboratory Infrared Spectra: 0.1 cm -1 Resolution (1ppm-m) Absorbance  10 6

Pacific Northwest National Laboratory Infrared Spectra: 0.1 cm -1 Resolution (1ppm-m) Absorbance Units 

Pacific Northwest National Laboratory High-Resolution Infrared Spectra 0.75 Torr 19.2 m cm -1

Pacific Northwest National Laboratory High-Resolution Infrared Spectra of Torr 19.2 m cm -1

Pacific Northwest National Laboratory Vibrational Assignments of CH 2 I 2 Assignment of the Fundamental Vibrational Frequencies

Pacific Northwest National Laboratory Remote Sensing: Atmospheric CH 2 I HI 1 ppm-m CH 2 I 2 1 ppm-m

Pacific Northwest National Laboratory Remote Sensing: Atmospheric CH 2 I 2 CH 2 I 2 1ppm-m CH ppm-m Wavenumber (cm ) Absorbance Units  10 6

Pacific Northwest National Laboratory Conclusions: CH 2 I 2 IR Spectrum  Complete Vibrational band origins observed (both Raman and Infrared) have been assigned in the C 2v point group  The two bands in the mid-IR, 8 and 9 are unresolved at 760 Torr, but at low Pressure are resolved. Laser monitoring (5 x OD)  Combination band Resolved C-type Band at 4426 cm -1 useful for laboratory or extractive work.  Combination or 2 1 Overtone at ~5940 cm -1 (both resolved) may also be useful for remote sensing Johnson, T.J., Masiello T., Sharpe S.W., Atmospheric Chemistry and Physics Discussions, 6, , 2006