Agnés Perrin

1. Update of methyl Chloride in the 3 µm region Agnés Perrin Laboratoire Interuniversitaire des Systémes Atmosphériques (LISA), CNRS, Université Paris XII, Créteil Agnes.Perrin@lisa.univ-paris12.fr C.Bray, D.Jacquemart, N. Lacome Laboratoire de Dynamique, Interactions et Réactivité (LADIR) , Université Pierre et Marie Curie-Paris 6, France

2. Importance of CH3Cl • Methylchloride (CH3Cl) is the most abundant, natural, chlorine-containing gas in the atmosphere, with natural sources like oceans and biomass burning as major identified sources.

3. Global methyl chloride (CH3Cl) measurements at 3µm • Recently solar occultation measurements performed at 3 µm by the ACE-FTS experiment on the SCISAT-1 satellite were used to get the first global distribution of methyl chloridein the upper troposphere and stratosphere. • However it was mentioned that the methyl chloride line parameters are of very low quality at 3 µm in both the HITRAN or GEISA databases • At 3 µm interferences exist between lines from Methyl chlorideandEthane (C2H6) (G.C.Toon) N.Weigum, C.Mcelcheran, K.A.Walker,J.R.Taylor, G.C.Toon, G.Manney and Y.Wang, TI09 64th Molecular Symposium, Columbus 2009}.

4. Infrared region for CH3Cl (image from the PNNL laboratory) and recent update in HITRAN

5. Infrared region for CH3Cl (image from the PNNL laboratory) and recent update in HITRAN A.Nikitin, J.P.Champion, and H. Bürger, J. Mol. Spectrosc. 230 , 174 (2005) A.Nikitin J.Mol. Spect 252 , 17 (2008) A.Nikitin and J.P.Champion, J. Mol. Spect 230 , 168 (2005) A.Nikitin et al. J. Mol Spect 221, 199 (2003)

6. Need to be updated Recent update in the HITRAN database Spectral region used by the ACE-FTS measurements A.Nikitin, J.P.Champion, and H. Bürger, J. Mol. Spectrosc. 230 , 174 (2005) A.Nikitin J.Mol. Spect 252 , 17 (2008) A.Nikitin and J.P.Champion, J. Mol. Spect 230 , 168 (2005)

8. Some Q-branches n1 band Parts of the (weaker ) n4 and 3n6 band .n1: Morillon, Graner J.Mol. Spectr (1969) .n4, 3n6(l=1) Jensen, Brodenson, Guelachvili, J.Mol.Spect(1981) Missing: the P- and R-branches of the n1 band

9. Goal of this study for methyl chloride (CH3Cl) • Perform a new analysis of the 3.3 µm region for methyl chloride (the 35Cl and 37Cl species) positions, intensities and line shape parameters • New FTS spectra recorded on the Bruker-FTS spectrometer of LADIR for pure CH3Cl and N2- CH3Cl samples • Analysis of line positions and intensities

10. Experimental conditions & Analysis Fourier transform spectra recorded on the Bruker IFS 120 HR (LADIR, Paris) for natural sample of CH3Cl, T=297K, 2830-3200 cm-1, R=0.008 cm-1. • Path length= 30cm, 0.5  P15.4 hPascal, (7 spectra), with one spectrum for P=0.5 hPascal & path length =415 cm. • Analysis of line positions and intensities for ~ 4500 assigned lines : • 35CH3Cln1, (1176, J 47, K  12); n4, (1532, J 41, K  13), 3n6 (l=1) (603, J 34, K  5). • 37CH3Cln1, (680, J 41, K  7); n4, (405, J 30, K  10) , 3n6 (l=1) ( 118, J 25, K  4).

11. Analysis for CH335Cl and CH337Cl parallel Perpendicular Perpendicular parallel

14. 3n6 (l=1) n4(l=1)strongly resonating 3n6 (l=1) andn4(l=1)resonating with n1 (l=0) Dark states 2n5(l=2), 2n3+n5(l=1) and 3n6(l=3) Six resonating states with l=0,1,2 and 3

15. Vibration-rotational |v, J, l, k> withl =0,±1,± 2 and ±3 , and -J k  J Diag part Hamiltonian: E v,l,k= Ev+(A-B)k2+ B.J(J+1)+ A zl.k • Resonances: • within each given vibrational state (v=v’, l l’) • between different vibrational states (vv’, l  l’). <v l J k| |v’,l’ J k’> resonances accounted for within theD(k- l)= 0  3n « Amat’s » selection rules .l’- l =-1  k’-k=+2 , -1, -4… .l’- l =+1  k’-k= -2 , +1, +4… l’- l =+2  k’-k= -1, +2, -4,.. l’- l =-2 k’-k= 1, -2, +4 … .l’- l =±3 k’-k= 0, ±3, … • Wötzel, Mäder, Harder, Pracna & Sarka, J. Mol. Struct. 780-781, p206 (2006) • Pracna, Müller, Urban, Horneman, & Klee, J. Mol. Spect. 256, p152 (2009)

16. Resonances < v l J k| | v’, l’ J k’ >in D(k-l)=0 3n D|l|=0 or 3 D|l|=2 D|l|=1

17. Line intensities • From a set of 200 experimental line intensities for the n1 (//-type) n4 and 3n6(l=1) (╨ type) bands of CH335Cl, the transition moment operators 1mzand 4mxof the n1 & n4 band was determined. • For the 3n6(l=1)band: 3n6mx=0 • (m=0 for the 2n3+n5, 2n5(l=2), 3n6(l=3) dark bands) • For CH337Cl, same (1mz& 4mx)transition moment operator for n1 & n4 than for CH335Cl

19. 10

22. Forbidden transition from the 2n3+n5 band

26. Resonance n4(l=1) k=2 3n6(l=3) k=0 Forbidden transition from the 3n6 (l=3) dark band

27. Conclusion • High resolution (Bruker) FTS spectra of natural CH3Cl were recorded at LADIR. • A large set of line positions and intensities were measured • A new extended analysis of the n1, n4, 2n6 bands of CH335Cl and CH337Cl was performed. • The calculations of line positions and intensities account for numerous resonances coupling the n1, n4,(l=1), 2n6(l=1) bright states with the 2n3+n5 (l=1), 2n5(l=2) and 3n6(l=3) dark states. • Future ongoing studies involve N2-broadening and line mixing studies. Financial support from INSU through the LEFE-CHAT program is gratefully acknowledged

28. Each J-matrix splits into 4 submatrices according to J, k, l • A1: (k-l)=3n and (J+k+l ) even • A2: (k- l)=3n and (J+k+ l ) odd • E3n+1 : (k- l)=3n+1 • E3n+2: (k- l)=3n+2 Exactely degenerate

29. Vibration-rotational |J, l, K> withl =0, 1, 2 and 3 A1: (k-l)=3n and (J+k+l ) even A2: (k- l)=3n and (J+k+ l ) odd E3n+1 : (k- l)=3n+1 E3n+2: (k- l)=3n+2 degeneracy Diag part Hamiltonian: E v,l,k= Ev+(A-B)K2+ B.J.(J+1)+ A zl.k • Resonances: • within each given vibrational state (v=v’, for l l’) • between different vibrational states (vv’, for l  l’). <v l J k| |v’, l’ J k’> resonances accounted for within the D(k- l )= 0  3n « Amat’s » selection rule Wötzel, Mäder, Harder, Pracna & Sarka, J. Mol. Struct. 780-781, p206 (2006)

30. Example of a resonance

31. Analysis parallel Perpendicular Perpendicular parallel + several dark interacting bands…