Formaldehyde; H2CO: bandes à 3.6 µm
Agnés Perrin
Laboratoire Interuniversitaire des Systémes Atmosphériques (LISA),
CNRS, Université Paris XII, Créteil, France
Perrin@lisa.univ-paris12.fr
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
1
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
2
Formaldehyde in the IR
.n2 band
5.7 µm
5.7 µm
3.6 µm
& 9 dark bands
.n4 n6
Int=1.2
Int=2.8
Intensity in 10-17 cm-1/(molecule.cm-2)
3
The 5.7 µm band of H2CO (n2 band at 1746 cm-1)
• Start to be used for the simultaneous detection of formaldehyde
(n2 band@1746cm-1) and formic acid (n3 band @1778 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:10.1029/2006JD007600, 2007
4
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 MIPAS5
Envisat spectra, Atmos. Chem. Phys., 2008
Formaldehyde in the IR
3.6 µm
.n1 & n5 bands
+ nine dark bands
Int=1.24
Int=2.79
Int in 10-17 cm-1/(molecule.cm-2)
6
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)
7
HITRAN: status of formaldehyde in the IR
3.6 µm
5.7 µm
3.6 µm: the HITRAN linelist ((2700-3000 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)
8
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)
9
The list in HITRAN is incomplete, incoherent (errors on the relative intensities)
10
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;221:192-198,
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;780-782:28-44.
11
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;221:192-198,
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;780-782:28-44.
12
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
Excellent line positions at
5.7 µm
Rather good (althouth not
perfect) for the 3.6 µm
region. Difficult calculation
5.7µm: [Perr03] Perrin, Keller, Flaud J Mol Spectrosc 2003;221:192-198,
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;780-782:28-44.
13
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 1600-3100cm-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;221:192-198,
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;780-782:28-44.
14
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:
1.
2.
3.
4.
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
15
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)
16
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;780-782:28-44.
[Brown79]: Brown, Hunt, & Pine J Mol Spect 75 406 (1979),
17
Status of the line intensities at 3.6 µm:
« Calculated band intensities » in 10-17.cm-1/molecule.cm-2 at 296K
Calc
HITRAN
Int=2.01
2700-3000cm-1
PNNL: Int=2.64
2700-3000 cm-1
LPMA
CH3Cl= 1.30
Ratio (PNNL/HITRAN) or (PNNL/Perr06)
Calc in 2006
Int=2.02
Perr06: Perrin, Valentin, Daumont J. Mol. Struct (2006)
PNNL= Sharpe et al. Appl Spectr. 2004;58:1452
18
Formaldehyde
Calculated band intensities in 10-17.cm-1/molecule.cm-2
Calc
PNNL: Int=2.85 (2600-3100 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
19
Intensities at 3.6 µm
• 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 75 406 (1979),
20
HITRAN
Comparison of the existing intensity data in the literature
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
21
HITRAN
Comparison of the existing intensity data in the literature
Ratio
(Int3.6µm/Int5.7µm)=1.7
highly improbable
Herndon et al 2005: double diode laser measurement @3.6 & 5.7 µm
22
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
23
Experimental details
New FTS (Bruker 120HR) spectra were recorded at LADIR
in the 1600-3100 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
24
Experimental details:
FTS spectrum recorded at LADIR in the 1600-3100 cm-1
(pure H2CO)
25
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 vibrationrotation resonances
26
Line intensity measurements & calculations
27
Line intensity measurements & calculations
On the average: INewILinda*1.30
28
HITRAN
Final band intensity calculation
This work
3.6 µm
5.7 µm
Ratio
Ratio (Int3.6µm/Int5.7µm)=2.2
29
Results at 5.7 µm: overview of the n2 band
30
Airborne measurements of H2CO and HCOOH by QCL spectrometer
Herndon, Zahniser, Nelson Jr., Shorter, McManus, Jiménez, Warneke, & de Gouw, J. Geophys.31Res.
D112, D10S03, doi:10.1029/2006JD007600, 2007
Results at 3.6 µm: significant improvements even on the relative scale
32
Hans et al. Atm Env. 16,969(1982)
Polluted air
of Los Angeles
LPMA
33
Detailed view of the 3.6 µm band
LADIR
34
Detailed view of the 3.6 µm band
LADIR
(Intensities*1.28)
35
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 %
36
H2CO: N2 -broadening studies at 5.7µm and 3.6 µm
-1
0,12
-1
N2-brodening coefficients in cm .atm
-1
0,14
N2-broadening coefficients in cm .atm
-1
measurements
0,10
0,08
0,06
0,04
(See David Jacquemart)
0,02
0.14
0.12
0.10
0.08
0.06
J"= 6
0.04
0.02
0.00
0,00
0
5
10
15
20
25
0
30
1
2
3
4
5
6
7
8
9
10
Ka"
No evidence of a vibrational dependence (5.7µm  3.6 µm)
Evidence of a J- and Ka rotational dependence of the linewidths
0.14
-1
0.12
-1
N2-broadening coefficients in cm .atm
-1
N2-broadening coefficients in cm .atm
-1
Jlow
0.10
0.08
0.06
0.14
0.12
0.10
0.08
0.06
ValidationJ"=8
and calculations are underJ"=
process
10
(see David Jacquemart & Bob Gamache)
0.04
0.02
0.00
0.04
0.02
0.00
0
1
2
3
4
5
Ka"
6
7
8
9
10
0
1
2
3
4
5
Ka"
6
7
8
37 9
10
Conclusion
• Using new FTS spectra recorded at high resolution
in the 1600-3100 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 (INSUCNRS).
38
Fridolin Kwabia Tchana
39
Vibrational bands
H
HCO
Vibration
antisym C-H stretching n5
sym C-H stretching n1
C-O stretching
CH2 bending
CH2 bending
out of plane bending
n2
n3
n6
n4
2n4, n4+n6, 2n6, n3+n4, n3+n6 n1, n5

B2
A1
H2CO Type
B
2843.3
A
2782.5
A1
A1
B2
B1
1746.0
1500.2
1249.1
1167.3
A
A
B
C
n2+n4, 2n3, n2+n6, n2+n3
2327, 2422, 2494, 2667, 2719, 2782, 2843cm-1, 2905, 2998, 3000, 3238
40
Problems with the HITRAN linelist at 3.6 µm
Missing lines
Relative
intensities
incorrect
Absolute scale:
HITRAN intensities
are too weak by 28%
41
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
41
61
31
21
41
W
61
31
21
A
B
c.c.
W
C.
C.
c.c.
c.c.
W
c.c.
c.c.
Anh
W
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;221:192-198,
5.7µm:[KWAB07] Kwabia Tchana , Perrin & Lacome , J Mol Spectrosc 2007;245:141
42
Energy level calculations for the 3.6 µm region
141,51,11,3161,3141 ,62,4161 42}
Hamiltonian
matrixnot
for perfect)
{2131, 2161for
,32, 2the
Rather
good (althouth
3.6 µm region.
interacting
statestwo
of bright
H2CO bands n1 and n5
Difficult calculation
involving
(2782 & 2844 cm-1) and 9 dark resonating dark bands.
v= 2131 2161 32 2141 51
2131 W C
B
2161 C W C A F
32
C W
C
1 1
A
W A
24 B
1
F C A W
5
11
F
C F B C
1 1
F C A F
36
3141
A B F A
62
C
4161
B
B
42
B
A-type Coriolis B-type
11 3161 3141
F
C F
A
F C
B
B A
F
C F
A
W C
B
C W A
B A W
F C
B
B
C
B
C-type
2
1 1
2
6 46 4
B
B
C B
F
C B
B C B
W A F
A W A
F A W
43
F anharmonic type interactions