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Agnés Perrin Laboratoire Interuniversitaire des Systémes Atmosphériques (LISA),
CNRS, Université Paris XII, CréteilAgnes.Perrin@lisa.univ-paris12.fr
C.Bray, D.Jacquemart, N. LacomeLaboratoire de Dynamique, Interactions et Réactivité (LADIR) ,
Université Pierre et Marie Curie-Paris 6, France
Update of methyl Chloride in the 3 µm region
Importance of CH3Cl
• Methyl chloride (CH3Cl) is the most abundant, natural, chlorine-containing gas in the atmosphere, with natural sources like oceans and biomass burning as major identified sources.
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 chloride in 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 chloride and Ethane (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}.
Infrared region for CH3Cl (image from the PNNL laboratory) and recent update in
HITRAN
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)
Recent update in the HITRAN database
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)
Spectral region used by the ACE-FTS measurements
Need to be
updated
Some Q-branches 1 band
Parts of the (weaker ) 4
and 36 band
Missing: the P- and R-branches of the 1 band
.1: Morillon, Graner J.Mol. Spectr (1969)
.4, 36(l=1) Jensen, Brodenson, Guelachvili, J.Mol.Spect(1981)
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
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 :
• 35CH3Cl 1, (1176, J 47, K 12); 4, (1532, J 41, K 13), 36 (l=1) (603, J 34, K 5).
• 37CH3Cl 1, (680, J 41, K 7); 4, (405, J 30, K 10) , 36 (l=1) ( 118, J 25, K 4).
Analysis for CH335Cl and CH3
37Cl
parallel
parallel
Perpendicular
Perpendicular
36 (l=1) 4 (l=1) strongly resonating
36 (l=1) and 4 (l=1) resonating with 1 (l=0)
Six resonating states with l=0,1,2 and 3
Dark states 25(l=2), 23+5(l=1) and 36(l=3)
Vibration-rotational |v, J, l, k> with l =0,±1,± 2 and ±3 , and -J k J
< v l J k| | v’, l’ J k’ > resonances accounted for
within the (k- l )= 0 3n « Amat’s » selection rules
Diag part Hamiltonian: E v,l,k= Ev+(A-B)k2+ B.J(J+1)+ A l.kResonances:
within each given vibrational state (v=v’, l l’)between different vibrational states (vv’, l l’).
•Wötzel, Mäder, Harder, Pracna & Sarka, J. Mol. Struct. 780-781, p206 (2006)•Pracna, Müller, Urban, Horneman, & Klee, J. Mol. Spect. 256, p152 (2009)
.l’- l =+1 k’-k= -2 , +1, +4…
l’- l =+2 k’-k= -1, +2, -4,..
.l’- l =±3 k’-k= 0, ±3 , …
.l’- l =-1 k’-k=+2 , -1, -4…
l’- l =-2 k’-k= 1, -2, +4 …
k|= 25
l =2
23+5
l=1
1
l=04
l=136
l=136
l=3
25 l=2 W 1, 2
23+5
l=1
W 1, 2
1 l=0 1, 2 1, 2 W 1, 2 0,3
4 l=1 1, 2 W 0,1,2 1, 2
36 l=1 0,1,2 W 1, 2
36 l=3 0,3 1, 2 1, 2 W
Resonances < v l J k| | v’, l’ J k’ > in (k-l)=0 3n
|l|=2|l|=1|l|=0 or 3
Line intensities• From a set of 200 experimental line intensities for
the 1 (//-type) 4 and 36(l=1) (╨ type) bands of CH3
35Cl, the transition moment operators 1z and 4x of the 1 & 4 band was determined.
• For the 36(l=1) band: 36x=0
• (for the 23+5, 25(l=2), 36(l=3) dark bands)
• For CH337Cl, same (1z & 4x) transition moment
operator for 1 & 4 than for CH335Cl
10
Forbidden transition from the 23+5 band
Resonance 4(l=1) k=2 36(l=3) k=0
Forbidden transition from the 36 (l=3) dark band
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 1, 4, 26 bands of
CH335Cl and CH3
37Cl was performed.• The calculations of line positions and intensities
account for numerous resonances coupling the 1, 4,(l=1), 26(l=1) bright states with the 23+5 (l=1), 25(l=2) and 36(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
Each J-matrix splits into 4 submatrices according to J, k, l
A1 A2 E(3n+1) E(3n+2)
A1
A2
E(3n+1)
E(3n+2)
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
Vibration-rotational |J, l, K> with l =0, 1, 2 and 3
< v l J k| | v’, l’ J k’ > resonances accounted for within the (k- l )= 0 3n
« Amat’s » selection rule
Diag part Hamiltonian: E v,l,k= Ev+(A-B)K2+ B.J.(J+1)+ A l.k
Resonances: within each given vibrational state (v=v’, for l l’)
between different vibrational states (vv’, for l 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
Wötzel, Mäder, Harder, Pracna & Sarka, J. Mol. Struct. 780-781, p206 (2006)
degeneracy
Example of a resonance
Analysis
parallel
parallel
Perpendicular
Perpendicular
+ several dark interacting bands…
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