1. Formaldehyde; H2CO: bandes à 3.6 µm
Agnés Perrin
Laboratoire Interuniversitaire des Systémes Atmosphériques (LISA), CNRS, Université Paris XII, Créteil, France
D.Jacquemart, F. Kwabia Tchana, N. Lacome
Laboratoire de Dynamique, Interactions et Réactivité (LADIR) , Université Pierre et Marie Curie-Paris 6, France
Many thanks to Larry Rothman and to the HITRAN committee

2. H2CO: of major tropospheric importance
Source of H2CO:
photo-oxydation of numerous hydrocarbones
Important for the status of the HOx
H2CO plays an important role in the cloud chemistry (liquid phase)
In non negligible concentration in the air of polluted industrial cities and during biomass burning
Can be measured in the MW, IR & UV/VIS spectral ranges
Astrophysical GOME SCIAMACHY

3. Formaldehyde in the IR .n2 band 5.7 µm & 9 dark bands Int=1.2 Int=2.8
.n4 n6
Int=1.2
Int=2.8
Intensity in cm-1/(molecule.cm-2)

4. The 5.7 µm band of H2CO (n2 band at 1746 cm-1)
Start to be used for the simultaneous detection of formaldehyde (n2 and formic acid (n3 cm-1) by pulsed Quantum Cascade Laser spectrometer (Herndon et al)
formic acid: n3 band, see our poster PII-05
Now used by the MIPAS FTS spectrometer on the ENVISAT satellite
 first H2CO profile in the lower stratosphere
Herndon, Zahniser, Nelson Jr., Shorter, McManus, Jiménez, Warneke, & de Gouw, J. Geophys. Res. D112, D10S03, doi: /2006JD007600, 2007

5. H2CO retrievals by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument
The 5.7 µm band used for H2CO retrievals by MIPAS on the ENVISAT satellite
Steck, Glatthor, von Clarmann, Fischer, Flaud, Funke, Grabowski, Höpfner, Kellmann, Linden, Perrin, and Stiller, Retrieval of global upper tropospheric and stratospheric formaldehyde (H2CO) distributions from high-resolution MIPAS-Envisat spectra, Atmos. Chem. Phys., 2008

6. Formaldehyde in the IR 3.6 µm .n1 & n5 bands Int=1.24 Int=2.79
+ nine dark bands
Int=1.24
Int=2.79
Int in cm-1/(molecule.cm-2)

7. Region of 3.6µm (n1 & n5bands)
Strongest IR band which coincides with a window of transparency of the atmosphere
Used for reliable portable IR environmental sensing of H2CO on ground-based, aircraft & satellite platforms……
Fourier transform spectroscopy [Yokelson et al, Rinsland et al]
Tunable Diode Laser Absorption Spectroscopy [Fried et al.] Difference-frequency –generation lasers (DFG) Instruments [Friedfeld, Fraser, Rehle, Curl , Richter, Tittel…] Cavity leak-out spectroscopy using CO –sideband laser [Dahnler et al ].
Presently: used by ACE (FTS instrument) onboard of the SCISAT satellite (Gaëlle Dufour and Peter Bernarth, Ch.Boone & co workers from the ACE team)

8. HITRAN: status of formaldehyde in the IR
3.6 µm: the HITRAN linelist (( cm-1) for H2CO was generated several years ago using, as input, the historical work of Linda Brown [Brown79].
This HITRAN linelist is incomplete, incoherent (errors on the relative intensities)
[Brown79]. Brown, Hunt & Pine, J. Mol Spectrosc. 75, 406 (1979)

9. Status of the HITRAN linelist at 3.6 µm for H2CO
Calc
LADIR
LPMA
CH3Cl
Calc in 2006
Perrin, Valentin, Daumont J. Mol. Struct (2006)

10. The list in HITRAN is incomplete, incoherent (errors on the relative intensities)

11. Goal of this work
Both the 5.7 µm and 3.6 µm bands are used for the retrieval of H2CO in the atmosphere (MIPAS & ACE).
The goal is to have accurate and reliable linelists (position, intensity, line shape parameters) in both spectral regions
…. But we generated recently two lists at 5.7 µm and 3.6 µm ….[Perr3, Kwab07, Perrr06]
5.7µm: [Perr03] Perrin, Keller, Flaud J Mol Spectrosc 2003;221: ,
5.7µm:[Kwab07] Kwabia Tchana , Perrin & Lacome , J Mol Spectrosc 2007;245:141
3.6 µm[Perrr06] Perrin, Valentin and Daumont J of Mol Struct 2006; :28-44.

12. These two line lists [Kwabia07, Perrin03] at 5
These two line lists [Kwabia07, Perrin03] at 5.7 µm and [Perrin06] at 3.6 µm respectively… need to be validated.
Quality of the line positions: achieved mainly from analyses of high resolution FTS spectra (LADIR, LPMAA, GSMA)
 depends on the complexity of the theoretical model…
5.7µm: [Perr03] Perrin, Keller, Flaud J Mol Spectrosc 2003;221: ,
5.7µm:[Kwab07] Kwabia Tchana , Perrin & Lacome , J Mol Spectrosc 2007;245:141
3.6 µm[Perr06] Perrin, Valentin and Daumont J of Mol Struct 2006; :28-44.

13. Quality of the line positions
The Hamiltonian matrix accounts for A-type Coriolis, B-type Coriolis, C-type Coriolis, Anharmonic type interactions
5.7 µm : the strong n2 band (at 1746 cm-1)
 3 dark bands (n3, n4 and n6 )
3.6 µm: the strong n1 & n5 bands
 9 dark bands
Rather good (althouth not perfect) for the 3.6 µm region. Difficult calculation
Excellent line positions at 5.7 µm
5.7µm: [Perr03] Perrin, Keller, Flaud J Mol Spectrosc 2003;221: ,
5.7µm:[Kwab07] Kwabia Tchana , Perrin & Lacome , J Mol Spectrosc 2007;245:141
3.6 µm[Perr06] Perrin, Valentin and Daumont J of Mol Struct 2006; :28-44.

14. In Refs [Perr03, Kwab03, Perr06]
Quality of the intensities for the linelists at 5.7 µm & 3.6 µm for H2CO:
In Refs [Perr03, Kwab03, Perr06]
the intensity calculations were performed using only experimental intensity data collected in the literature.
(1) Band intensity measurements (low or medium resolution in cm-1) coverning simultaneously both the 5.7 µm and 3.6 µm regions
Intercomparison ???
(2) Individual line intensities at 3.6 µm
5.7µm: [Perr03] Perrin, Keller, Flaud J Mol Spectrosc 2003;221: ,
5.7µm:[Kwab07] Kwabia Tchana , Perrin & Lacome , J Mol Spectrosc 2007;245:141
3.6 µm[Perr06] Perrin, Valentin and Daumont J of Mol Struct 2006; :28-44.

15. How from line by line intensity mesurements (at 3
How from line by line intensity mesurements (at 3.6 µm ) can we deduce « band intensities at 3.6 µm » and perform Intercomparaison of the band intensities (5.7 µm  3.6 µm) ?????
Uneasy… but possible !!: It is necessary to compute the « total » band intensity. For this goal one must:
Use a good theoretical model which is able to reproduce the individual line intensities in the overall spectral range
Compute a « synthetic spectrum » (list of line positions and intensities)
Sum the individual line intensities in the spectral range covered by the absorbing band
Account correctly from the contributions from the hot bands and for the minor isotopic species

16. Low and medium resolution
1-Existing band intensities in the literature
Low and medium resolution
band intensity measurements for the whole (3.6 to 5.7 µm) spectral range
(PNNL) Sharpe, Johnson, Sams, Chu, Rhoderick, Johnson, Appl Spectrosc 58, 1452 (2004)

17. 2- Individual line intensities in the literature (at 3.6 µm only)
At 3.6 µm: the extensive set of individual line intensities measured by Brown et al. [Brown79]
HITRAN : the intensities from Brown-79 were used as a starting point for the generation of the HITRAN linelist at 3.6 µm) .
This set of individual line intensities [Brown79] was also used in the 3.6 µm linelist of Ref. [Perr06]
[Perr06] Perrin, Valentin and Daumont J of Mol Struct 2006; :28-44.
[Brown79]: Brown, Hunt, & Pine J Mol Spect (1979),

18. Status of the line intensities at 3.6 µm:
« Calculated band intensities » in cm-1/molecule.cm-2 at 296K
Calc
HITRAN
Int=2.01
cm-1
PNNL: Int=2.64
cm-1
LPMA
Ratio (PNNL/HITRAN) or (PNNL/Perr06) = 1.30
CH3Cl
Calc in 2006
Int=2.02
Perr06: Perrin, Valentin, Daumont J. Mol. Struct (2006)
PNNL= Sharpe et al. Appl Spectr. 2004;58:1452

19. Calculated band intensities in 10-17.cm-1/molecule.cm-2
Formaldehyde
Calculated band intensities in cm-1/molecule.cm-2
Calc
PNNL: Int=2.85 ( cm-1)
LPMA
Ratio: (PNNL/Perr06)= 1.30
CH3Cl
Perr06:
Int=2.16
Perr06: Perrin, Valentin, Daumont J. Mol. Struct (2006)
PNNL= Sharpe et al. Appl Spectr. 2004;58:1452

20. Intensities at 3.6 µm  Sorry Linda !! 
The individual line intensities generated several years ago by Linda Brown & coworkers [BROW79] lead to intensities about 30% weaker than those achieved from recent band intensities measurements
 Sorry Linda !! 
[BROW-79: Brown, Hunt, & Pine J Mol Spect (1979),

21. Ratio (Int3.6µm/Int5.7µm)=1.7 highly improbable
Comparison of the existing intensity data in the literature
HITRAN
Perr06: (3.6 µm) intensities scaled to Brown 79
Perr03 (5.7 µm) intensities scaled to Nakanaga
2.2
Ratio (Int3.6µm/Int5.7µm)=1.7 highly improbable

22. Ratio (Int3.6µm/Int5.7µm)=1.7 highly improbable
Comparison of the existing intensity data in the literature
HITRAN
Ratio (Int3.6µm/Int5.7µm)=1.7 highly improbable
Herndon et al 2005: double diode laser & 5.7 µm

23. Purpose of this work
The measurement of accurate individual line intensities and self- & N2-broadened line width (high resolution FTS spectra)
Intensity calculation and update of the databases

24. Recording of the spectra
Experimental details
New FTS (Bruker 120HR) spectra were recorded at LADIR in the cm-1 for pure H2CO and for N2-broadened H2CO
Conditions of the FTS recordings (pressure, temperature) were optimized in order to avoid decomposition (and/or) polymerization of H2CO.
Pressure in the cell
Recording of the spectra 8h 2h
Time

25. Experimental details:
FTS spectrum recorded at LADIR in the cm-1 (pure H2CO)

26. Line intensity measurements and calculations
A large set of individual line intensities were measured in both the 5.7 µm and 3.6 µm regions using the multifit program developed at LPMAA
From these intensities the expansion of the transition moment operators of the expansion of the transitions moments operators for the n2, n3, n4 and n6 bands at 5.7 µm (resp. 2n4, n4+n6, 2n6, n3+n4, n3+n6, n1, n5, n2+n4, 2n3, n2+n6 and n2+n3 bands at 3.6 µm ).
The calculations account for the various vibration- rotation resonances

27. Line intensity measurements & calculations

28. Line intensity measurements & calculations
On the average: INewILinda*1.30

29. Final band intensity calculation This work
HITRAN
3.6 µm
5.7 µm
Ratio
Ratio (Int3.6µm/Int5.7µm)=2.2

30. Results at 5.7 µm: overview of the n2 band

31. Airborne measurements of H2CO and HCOOH by QCL spectrometer
Herndon, Zahniser, Nelson Jr., Shorter, McManus, Jiménez, Warneke, & de Gouw, J. Geophys. Res. D112, D10S03, doi: /2006JD007600, 2007

32. Results at 3.6 µm: significant improvements even on the relative scale

33. Hans et al. Atm Env. 16,969(1982)
Polluted air
of Los Angeles
LPMA

34. Detailed view of the 3.6 µm band
LADIR

35. Detailed view of the 3.6 µm band
LADIR
(Intensities*1.28)

36. Region of 3.6µm (n1 & n5bands)
Used for reliable portable IR environmental sensing of H2CO on ground-based, aircraft & satellite platforms……
Fourier transform spectroscopy [Yokelson et al, Rinsland et al]
Tunable Diode Laser Absorption Spectroscopy [Fried et al.] Difference-frequency –generation lasers (DFG) Instruments [Friedfeld, Fraser, Rehle, Curl , Richter, Tittel…] Cavity leak-out spectroscopy using CO –sideband laser [Dahnler et al ].
!!!  !!!!
All these atmospheric measurements which were retrieved using HITRAN lead to an overestimation of H2CO of 28 %

37. H2CO: N2 -broadening studies at 5.7µm and 3.6 µm
(See David Jacquemart)
No evidence of a vibrational dependence (5.7µm  3.6 µm)
Evidence of a J- and Ka rotational dependence of the linewidths
Validation and calculations are under process (see David Jacquemart & Bob Gamache)

38. Conclusion
Using new FTS spectra recorded at high resolution in the cm-1 spectral range at LADIR a large set of line intensities were measured.
It was possible to determine the absolute intensities both in the 5.7 µm and 3.6 µm regions
The intensities are now coherent in both spectral regions
N2- and -self line broadening parameters were measured. Calculations are under process.
The authors gratefully acknowledge a financial support from the French research program "Les Enveloppes Fluides et l'Environnnement, Chimie Atmosphérique" (LEFE-CHAT) from Institut National des Sciences de l'Univers" du CNRS (INSU-CNRS).

39. Fridolin Kwabia Tchana

40. Vibrational bands n1, n5 2n4, n4+n6, 2n6, n3+n4, n3+n6
2327, 2422, 2494, 2667, 2719,
2782, 2843cm-1,
2905, 2998, 3000, 3238

41. Problems with the HITRAN linelist at 3.6 µm
Missing lines
Relative intensities incorrect
Absolute scale: HITRAN intensities are too weak by 28%

42. Hamiltonian matrix for {21, 31,41,61} interacting states of H2CO
Line position calculations for the 5.7 µm region: (the strong n2 band (at 1746 cm-1) is resonating with the n3, n4 and n6 weak bands)
Infrared data: FTS spectra recorded at LADIR for the n2 band
Hamiltonian matrix for {21, 31,41,61} interacting states of H2CO
A-type Coriolis, B-type Coriolis , C-type Coriolis
Anh anharmonic type interactions
Excellent line positions at 5.7 µm
5.7µm: [PERR03] Perrin, Keller, Flaud J Mol Spectrosc 2003;221: ,
5.7µm:[KWAB07] Kwabia Tchana , Perrin & Lacome , J Mol Spectrosc 2007;245:141

43. F anharmonic type interactions
Energy level calculations for the 3.6 µm region Hamiltonian matrix for {2131, 2161,32, 2141,51,11,3161,3141 ,62, } interacting states of H2CO
Rather good (althouth not perfect) for the 3.6 µm region. Difficult calculation involving two bright bands n1 and n5 (2782 & 2844 cm-1) and 9 dark resonating dark bands.
A-type Coriolis
F anharmonic type interactions
B-type
C-type