9th HITRAN Database & Atmospheric Spectroscopy Applications conferences Formaldehyde broadening coefficients Agnès Perrin Laboratoire Interuniversitaire

9th HITRAN Database & Atmospheric Spectroscopy Applications conferences

Formaldehyde broadening coefficients

Agnès Perrin Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS,

Université Paris XII, Créteil, France

Hamiltonian constants

David Jacquemart, Fridolin Kwabia-Tchana, and Nelly LacomeLaboratoire de Dynamique, Interactions et Réactivité (LADIR), CNRS, Université

Pierre et Marie Curie-Paris 6, France

HR FT spectra and line broadening measurements

Anne Laraia and Bob Gamache Department of Environmental, Earth & Atmospheric Sciences

University of Mass. Lowell, USA

Calculation of broadening parameters


- Two spectral regions of atmospheric interest:

around 3.5 µm (2600-3200 cm-1) complete update in HITRAN 2008

around 5.7 µm (1700-1800 cm-1) new line list available in HITRAN 2008

Bruker HR120-FTS spectrum recorded at LADIR


2 band

1, 5 + 6 other bands


Summary of the presentation

1/ Experimental measurements of both self- and N2-broadening coefficients

2/ Empirical model for the rotational dependence of broadening coefficients

3/ Theoretical calculation of N2-broadening coefficients and their temperature exponents

4/ Comparison with literature


Multispectrum fitting procedure

→ 284 transitions at 5.7 µm region

→ 456 transitions at 3.5 µm regionSelf-and N2-broadening coefficients


In HITRAN:

Self-widths fixed to 0.00 cm-1/atm

Air-widths fixed to 0.107/0.108 cm-1/atm

0 5 10 15 20 25 30

0.0

0.2

0.4

0.6

0.8

1.0

Jlow

5.7 µm spectral region 3.5 µm spectral region

Se

lf-b

roa

de

nin

g c

oe

ffic

ien

ts in

cm

-1/a

tm

0 5 10 15 20 25 30

0.06

0.08

0.10

0.12

0.14

N2-

bra

od

en

ing

co

eff

icie

nts

in c

m-1/a

tm

Jlow



0 2 4 6 80.00

0.02

0.04

0.06

0.08

0.10

0.12

Ka

N2-

bra

od

en

ing

co

eff

icie

nts

in c

m-1/a

tm

2

1

5

24

26

3+

6

Ka dependence of the N2-broadening coefficients

obtained at 3.5 and 5.7 µm

Transitions having same value of Jlow = 8







0 5 10 15 20 25 30

0.06

0.08

0.10

0.12

0.14

N2-

brao

deni

ng c

oeff

icie

nts

in c

m-1/a

tm

Jlow


0 1 2 3 4 5 6 7 8 9 100.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

N2-

bro

ad

en

ing

co

eff

icie

nts

in c

m-1.a

tm-1

Ka"

J" = 6

0 1 2 3 4 5 6 7 8 9 100.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

J " = 8

Ka"

N2-

broa

deni

ng c

oeff

icie

nts

in c

m-1.a

tm-1

0 1 2 3 4 5 6 7 8 9 100.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

J" = 10

Ka"

N2-

broa

deni

ng c

oeff

icie

nts

in c

m-1.a

tm-1

No evidence of a vibrational dependence (5.7µm 3.6 µm)

Evidence of a J- and Ka-rotational dependence of the linewidths


0 10 20 30 40 500.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

Ka

2

N2-

bra

od

en

ing

co

eff

icie

nts

in c

m-1/a

tm

2

1

5

24

26

3+

6

0 2 2( )J a J J aK a a K For each set of γ having same J’’ value:

J’’ = 8


Empirical parameters describing the J-and Ka-rotational dependence of the N2-broadening coefficients

0 2 2( )J a J JK a a K


Empirical parameters describing the J-and Ka-rotational dependence of the self-broadening coefficients

0 2 2( )J a J J aK a a K


Line broadening (self and by N2) can easily be calculated using these constants

JQSRT 111 (2010), 1209-1222.

0 2 2( )J a J J aK a a K








Complex Robert-Bonamy formalism

for N2-broadening coefficients

Calculation done for the 2 band

→ Constants for dipole moment of H2CO, for quadrupole of H2CO and N2 taken from literature

→ Parameters for Lennard-Jones atom-atom potential have been manually fitted to match a reduced set of N2-broadening measurements


Comparison between

measurements, empirical model and theoretical calculation (CRB)

T = 296 K


Comparison between

measurements, empirical model and theoretical calculation (CRB)

T = 296 K


CRB calculation of N2-broadening coefficients at 296 K


Temperature exponent based on CRB formalism calculations

at various temperatures

Set of 7 temperatures:

200, 225, 275, 296, 350, 500, 700 K


Temperature exponent from CRB calculations (200-350 K)

In HITRAN 2008:

nair fixed to 0.7








Comparison for low Ka values


Conclusion

→ Measurements of self- and N2-line widths at 296K (for more than 700 transitions)

→ Empirical model to reproduce the rotational dependence of the measurements

→ CRB calculation of N2 widths for temperatures ranging from 200 to 700K

→ Temperature exponents for the N2-widths derived from CRB calculations

Generation of self-, air-widths, and nair for HITRAN 2008 line list

(available as supplementary materials of JQSRT 111(2010), 1209-1222.)


In the special issue dedicated to Larry

Thanks for your attention…




Sample of the 5.7-µm spectral region





0 2 2( )J a J JK a a K For each set of γ having same Jlow value:

Jlow = 8

Documents

9th HITRAN Database & Atmospheric Spectroscopy Applications conferences Formaldehyde broadening coefficients Agnès Perrin Laboratoire Interuniversitaire