1. 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 99352 Quantitative IR Spectra and Vibrational Assignments of CH 2 I 2, an Atmospheric Aerosol Precursor

2. 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 0 3100 3000 2900 2800 2700 http://nwir.pnl.gov

3. 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 10 -3 OD at 10  m  DATA FORMAT:.txt and.spc format, 1 ppm-m  NOTES:Export restricted from sensitive countries http://nwir.pnl.gov

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

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

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

7. Pacific Northwest National Laboratory Infrared Spectra: 0.1 cm -1 Resolution (1ppm-m) Absorbance Units  10 6 8 9

8. Pacific Northwest National Laboratory High-Resolution Infrared Spectra 0.75 Torr 19.2 m 0.0025 cm -1

9. Pacific Northwest National Laboratory High-Resolution Infrared Spectra of 6 0.75 Torr 19.2 m 0.0025 cm -1

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

11. Pacific Northwest National Laboratory Remote Sensing: Atmospheric CH 2 I 2 2 + 6 HI 1 ppm-m CH 2 I 2 1 ppm-m

12. Pacific Northwest National Laboratory Remote Sensing: Atmospheric CH 2 I 2 CH 2 I 2 1ppm-m CH 4 1.8 ppm-m 1 + 6 2 1 0 5 10 15 20 58605880590059205940596059806000 Wavenumber (cm ) Absorbance Units  10 6

13. 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 10 -7 OD)  2 + 6 Combination band Resolved C-type Band at 4426 cm -1 useful for laboratory or extractive work.  1 + 6 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, 1275-1299, 2006