1. Marlon Ramos and Brian J. Drouin 6/23/2011 1 THz Spectrum of Methyl Bromide (CH 3 Br)

2.  Natural: Oceans: Algae, Kelp Continental : Vegetation, biomass burning  Commercial: leaded gas pesticide fire retardant 6/23/2011 2 THz Spectrum of Methyl Bromide (CH 3 Br)

3.  Commercially man-made sources have led to an increase of CH 3 Br levels in our atmosphere: CH 3 Br has an ozone depletion potential of 0.2% and falls under regulations of the Clean Air Act b  Constant exposure to CH 3 Br is highly toxic a : Long term Inhalation of 1,600 ppm in a time interval of [10,20] hours, or 7,900 ppm for 1.5 hours is lethal to humans or can also lead to neurological damage Short term exposure might cause lung damage to humans THz Spectrum of Methyl Bromide (CH3Br)6/23/2011 3

4.  Because It is an ubiquitous component of our earth’s atmosphere and of because of increasingly concerning levels of CH 3 Br In our oceans and atmosphere: The California Birth Defects Prevention Act of 1984 (SB 950) requires that all pesticides (such as CH 3 Br) be supported by health testing data. In 1991, the for ‘lack of testing data,’ the EPA scheduled a phase-out of CH 3 Br, which started in the year 2000. 6/23/2011 4 THz Spectrum of Methyl Bromide (CH 3 Br)

5. Ozone Depletion Process Cycle happens in the stratosphere at tropical and middle latitudes where ultraviolet sunlight is most intense. Cycle begins with BrO or Br BrO with O = Br Br with reacts by destroying ozone and reforming BrO, loops all over again. Br or BrO is reformed each time an ozone molecule is destroyed, Br is considered a catalyst for ozone destruction. Atomic oxygen (O) forms when ultraviolet sunlight reacts with ozone and oxygen molecules 6/23/2011 5 THz Spectrum of Methyl Bromide (CH 3 Br)

6.  Even though CH 3 Br might seem very useful and promising, its use has environmental impacts and health concerns.  How do we accurately measure levels of CH 3 Br in our environment?  Microwave Limb Sounding?  BrO - N.J. Livesey, et. al, Geophys. Res. Lett. 33 (2006) L20817.  CH3Cl - N.J. Livesey, et. al, JPL publication D-33509; http://mls.jpl.nasa.gov/data/v3-3_data_quality_document.pdf  Accurately measure and detect CH 3 Br will allow us a better understanding of its effect in our environment. 6/23/2011 6 THz Spectrum of Methyl Bromide (CH 3 Br)

7. 1)W. Gordy, J. W. Simmons and A. G. Smith, Phys. Rev. 74 (1948) 243 – 249. 2)A. H. Sharbaugh, J. Mattern, Phys. Rev. 75, (1949) 1102. 3) J. W. Simmons, W. O. Swan, Phys. Rev. 80, (1950) 289. 4) J. W. Simmons, W. E. Anderson, Phys. Rev. 80, (1950) 338. 5) J. Kraitchman, B. P. Dailey, J. Chem. Phys. 22, (1954) 1477. 6)W. J. Orville Thomas et al., J. Chem. Phys. 22, (1954) 1718. 7)Y. Morino and C. Hirose, J. Mol. Spec. 24 (1967) 204 – 224. 8)T.E. Sullivan, L. Frenkel, J. Mol. Spec. 39 (1971) 185 – 201. 9)J. Demaison et al., J. Chem. Phys. 67, (1977) 254. 10)B. Duterage, et. al, Compt. Rend. Acad. Sci. Paris B, 284 (1977) 213 - 215. 11) M. V. Moskienko, S.F. Dyubko, Opt. Spectrosc., 43, (1977) 503. 12)K.-F. D¨ossel, D. H. Sutter, Z. Naturforsch 34a, (1979) 469. 13) J. R. Williams, S. G. Kukolich, J. Mol. Spectrosc. 74, (1979) 242. 14)W.A. Wensink et al., J. Phys. B 13, (1980) 4009. 15) S. G. Kukolich, C. D.Cogley, J. Chem. Phys. 77 (1982) 1685; erratum 77, (1982) 581. 16) R. Bocquet et al., Europhys. Lett. 2 (1986) 275. 17)R. Bocquet et al., J. Mol. Spectrosc. 164, (1994) 456. Axial Constants (from IR GSCDs) 1)F. Lattanzi, C. di Lauro, G. Guelachvili, Mol. Phys. 45 (1982) 295. 2)J. Sakai, M. Katayama, J. Mol. Struct. 190 (1988) 113. 3)F. Kwabia Tchana, et. Al, J. Mol. Spectrosc. 228 (2004) 441 - 452. 6/23/2011 7 THz Spectrum of Methyl Bromide (CH 3 Br)

8.  Focus on Rotational data and infrared ground state combination differences  SPFIT/ SPCAT (suite) is used to fit the data which in turn generates predictions for the JPL catalog.  Most data of high quality especially in the millimeter wavelengths: 1)T.E. Sullivan, L. Frenkel, J. Mol. Spec. 39 (1971) 185 – 201. 2)J. Demaison et al., J. Chem. Phys. 67, (1977) 254. 3)B. Duterage, et. al, Compt. Rend. Acad. Sci. Paris B, 284 (1977) 213 - 215.  Submillimeter work was ok up to 800 GHz, but marginal above 1)R. Bocquet et al., Europhys. Lett. 2 (1986) 275. 2)R. Bocquet et al., J. Mol. Spectrosc. 164, (1994) 456.  Very little work done on 13 CH3Br  We happened to have a sample of 90% enriched 13 CH3Br 6/23/2011 8 THz Spectrum of Methyl Bromide (CH 3 Br)

9.  Experiments were performed at room temperature utilizing an isotopically (90%) enriched sample of 13 CH 3 Br. Spectra were recorded from 750 - 1200 GHz, assignments where made that covered CH 3 79 Br, CH 3 81Br, 13 CH 3 79 Br and 13 CH 3 81 Br isotopologues at J < 66 and K < 17 for the ground vibrational states.  12 CH 3 Br transitions where observed at 10% the signal level of corresponding to 13 C transitions. During detection, the pressure chosen for 13 CH 3 Br produced saturation of lines at J≤66 and K≤9. 6/23/2011 9 THz Spectrum of Methyl Bromide (CH 3 Br)

10. 4 sources scanned from 750-1200 GHz at 200 kHz resolution - 1.5 million data points! H 2 O (atmospheric spectrum) Overlap of sources Gap between sources All data 6/23/2011 10 THz Spectrum of Methyl Bromide (CH 3 Br)

11. At 0.8 THz J = 41 6/23/2011 11 THz Spectrum of Methyl Bromide (CH 3 Br)

12. At 1.2 THz J = 61 6/23/2011 12 THz Spectrum of Methyl Bromide (CH 3 Br)

13. Model used to fit the spectrum, which can determine A, B, D, H Energy and Transition states: Lowest = Ground State, Highest = Upper State, Middle = Transitional 6/23/2011 13 THz Spectrum of Methyl Bromide (CH 3 Br)

14. Frequency precision fits to 8 significant figures, our model fits to all eight 6/23/2011 14 THz Spectrum of Methyl Bromide (CH 3 Br)

15. fixed axial and hfs for 13C 6/23/2011 15 THz Spectrum of Methyl Bromide (CH 3 Br)

16. * All of the residuals were biased positive 6/23/2011 16 THz Spectrum of Methyl Bromide (CH 3 Br)

17. 6/23/2011 17 THz Spectrum of Methyl Bromide (CH 3 Br)

18.  CH 3 Br is an important species known to be active in our atmosphere.  It is important to improve the understanding of less complex molecules in order to have a better understand on how to approach more complex molecules.  This study improves the spectroscopic database for CH 3 Br at the 1.2 THz range  We have submitted a manuscript for publication to the Journal of Molecular Spectroscopy, describing this work and the results.  Microwave limb sounding (MLS) is currently detecting methyl chloride (CH 3 Cl )and Bromine monoxide (BrO); utilizing their THz spectra, we hope this characterization of the THz spectrum of CH 3 Br will lead to a method to monitor it globally. 6/23/2011 18 THz Spectrum of Methyl Bromide (CH 3 Br)

19. Jet Propulsion Laboratory California Institute of Technology Pasadena, California www.nasa.gov NASA Undergraduate Student Research Program (USRP)  Molecular Spectroscopy Group : Timothy Crawford, Shanshan Yu, Harshal Gupta and Keeyoon Sung  Petra.A.Kneissl-Milanian (USRP Advisor) 6/23/2011 19 THz Spectrum of Methyl Bromide (CH 3 Br)