Laser spectroscopic study of ozone in the 100←000 band for the SWIFT instrument

M. Guinet, C. Janssen, D. Mondelain, C. Camy-PeyretLPMAA, CNRS- UPMC (France)

18/06/2010

Importance of ozone in terrestrial atmosphere

• In the stratosphere: UV filter for solar radiation• Key role in tropospheric chemistry (OH radical precursor)• Green house gas

Studied by a large palette of instruments (UV spectrophotometer, Dobson spectrometer, FTIR…)

1% uncertainty for intensity is required for atmospheric applications (reactive gas!)

Comparison of published data sets → several % inconsistencies for intensities (10 µm bands)

- O3: tracer for atmospheric winds (SWIFT instrument)

- Stratospheric wind speed (Doppler shift) & ozone concentration measurements

- Understand the transport of O3 in the stratosphere

High accuracies required (for the 15 strong 16O3 transitions)

- Absolute positions: 5 10-5 cm-1 ( 13 m s-1)

- Absolute intensities: 1%

Other spectroscopic parameters measured: air, air, self

SStratospheric WWind IInterferometerFFor TTransport studies (SWIFT)

A set up at the border of metrology and spectroscopy

0 50 100 150 200 250 300

-1,0

-0,5

0,0

0,5

1,0 ?

0 100 200 300 400 500

-1,0

-0,5

0,0

0,5

1,0

Laser Diode

/ < 4.10-8

8.9 µm

Stabilization principle

Stabilized HeNe

/ = 10-8

633 nm

Michelson interferometer

KIR

HeNe

A set up at the border of metrology and spectroscopy

0 50 100 150 200 250 300

-1,0

-0,5

0,0

0,5

1,0 ?

Laser Diode

/ < 4.10-8

0 100 200 300 400 500

-1,0

-0,5

0,0

0,5

1,0Stabilized HeNe

/ = 10-8

Michelson interferometer

Stabilization principle

Stabilized HeNe

/ = 10-8

633 nmLaser Diode

/ < 4.10-8

8.9 µm

A set up at the border of metrology and spectroscopy

0 50 100 150 200 250 300

-1,0

-0,5

0,0

0,5

1,0 ?

Laser Diode

/ < 4.10-8

0 100 200 300 400 500

-1,0

-0,5

0,0

0,5

1,0Stabilized HeNe

/ = 10-8

Michelson interferometer

Stabilization principle

Stabilized HeNe

/ = 10-8

633 nmLaser Diode

/ < 4.10-8

8.9 µm

A set up at the border of metrology and spectroscopy

0 50 100 150 200 250 300

-1,0

-0,5

0,0

0,5

1,0 ?

Laser Diode

/ < 4.10-8

0 100 200 300 400 500

-1,0

-0,5

0,0

0,5

1,0Stabilized HeNe

/ = 10-8

Michelson interferometer

Stabilization principle

Stabilized HeNe

/ = 10-8

633 nmLaser Diode

/ < 4.10-8

8.9 µm

A set up at the border of metrology and spectroscopy

0 50 100 150 200 250 300

-1,0

-0,5

0,0

0,5

1,0 ?

Laser Diode

/ < 4.10-8

Amplitude modulation scheme good S/N (several thousand)

Both highly tunable and stabilized system

Ultra flexible setup (atmospheric windows accessible)

0 100 200 300 400 500

-1,0

-0,5

0,0

0,5

1,0Stabilized HeNe

/ = 10-8

Michelson interferometer

Stabilization principle

Stabilized HeNe

/ = 10-8

633 nmLaser Diode

/ < 4.10-8

8.9 µm

Stabilized spectrometer

LaserDiode

O3 Generation

UVO3

N2O

(FP)D

D

C D

PT 100

D

LaserDiode

UV O3 Generation system

Step by step modeStep < 10-4 cm-1

S/N : 3000I0

FPN2O Accuracy (2):

Position < 8.10-5 cm-1

Intensity < 2%

M. Guinet, D. Mondelain, C. Janssen, C. Camy-Peyret, JQSRT, 111, 961-972 (2010)

Interferometer locked onto stabilized HeNe laser

Spectra

Linearization

Absolute calibration

SWIFT Line

10 000 points

Metrological approachReduction and taking into account of systematic biases : Sample purity, spectrometer, experimental conditions…

Traceability :

Following the BIPM recommendation (photometer UV).Calibrated tools (PT 100, micrometer, pressure gauge, stabilized HeNe).

Expertise :O3 sample purity test (> 99.5 % purity sample) :

IR spectrometer (CO2, H2O, N2O)

mass spectrometer (N2, NOx)

pressure (O2, N2, non condensable gases),

Stable conditions (temperature, very low ozone decomposition 2- 4 ‰ / hour)

Checking :

Check BIPM UV recommended cross section (Hearn) with a calibrated pressure gauge.

C. Janssen and M. Guinet, RSI., submitted

Hearn A. G., Proc. Phys. Soc., 78 (1961) 932-940

Mass spectrometer

High accuracy absorption measurement of O3 cross

section at 253.65 nm

International standard (BIPM) :

our measures :

M. Guinet, C. Camy-Peyret, D. Mondelain and C. Janssen, Refinement of the ozone standard – absolute ozone absorption cross section at the mercury emission line position 253.65 nm, Metrol., en préparation

= 1.14710-17cm² (± 2.1%)

= 1.13110-17cm² (± 0.7%)

• Estimated uncertainties between 0.8 and 1.3% considering:– statistical error over the 11 spectra with pure O3

– systematic errors (T, offset, UV, LUV, LIR…)

Results on intensities

Comparison with HITRAN08:-2.2 1.1(2) %

(Our UV cross section)

-2.6 1.3(2)

(Mauersberger cross section)

• Cross cell : UV and IR measured simultaneously

3.6% inconsistencies between UV (Hearn) and IR (HITRAN 08) recommended values in agreement with Picquet-Varrault

Results on intensities

Picquet-Varrault et al, J. Phys. Chem A, 109 (2005) 1008-1014.

UV

IR

Absolute positions of strong O3 lines

• The N2O line positions were accurately measured by an heterodyne experiment (Maki and Wells)

• Linearization and calibration procedure applied to O3 and N2O spectra

N2O positions → overall accuracy of 8 10-5 cm-1 (2)

Wind speed uncertainty: ~ 20 m s-1

O3 positions →

Mean difference

with HITRAN08:

(5 8 (2))10-5 cm-1

Maki A.G., Wells J.S. NIST Special publication (1991) 821

Determination of the self pressure broadening

• Ultra high resolution spectra

(200 – 1000 points / line)• Voigt and Rautian-Sobel'man

(hard) line profile• Multi-fit procedure

Pressure broadening at 2 % accuracy level (2)

Agrees with HITRAN by 0.6% with Smith by 1.7%(Voigt profile)

HITRAN [cm-1]

HITRAN [cm-1atm-1]

This work [cm-1atm-1] (Voigt)

This work - HITRAN

[%]

This work [cm-1atm-1] (Hard)

1132.59927 0.1031 0.10372(15) 0.60 0.10540(17) 1132.60340 0.1035 0.10421132.65698 0.0964 0.09594(8) -0.48 0.09660(7) 1132.78600 0.0963 0.09691132.81144 0.1023 0.10160(11) -0.68 0.10222(12)

1133.43351 0.1033 0.10706(6) 3.64 0.10753(6) 1133.58691 0.1033 0.10415(15) 0.82 0.10488(15)1133.63170 0.0948 0.09630(9) 1.58 0.09678(8)1133.67120 0.0958 0.09331(11) -2.60 0.09362(11)1133.72456 0.1017 0.10289(12) 1.17 0.10370(12)1133.97863 0.0917 0.09231134.02880 0.0954 0.09736(8) 2.06 0.09777(9)1134.25147 0.1032 0.10675(12) 3.441134.45383 0.0952 0.09272(9) -2.611134.50970 0.1010 0.10169(8) 0.68

Air-pressure broadening coefficients

8 absorption spectra recorded with the crossed UV-IR cell and a 50 m astigmatic cell (O3 decomposition <1% / hour)

Astigmatic cellHITRAN [cm-1]

air

[cm-1atm-1]n air

1132.59927 0.07902(4)

1132.60340 0.0853

1132.65698 0.07171(1) 0.71

1132.78600 0.06844(1) 0.72

1132.81144 0.07703(2) 0.48

1133.43351 0.08432(3) 0.51

1133.58691 0.0752

1133.63170 0.06994(1) 0.92

1133.67120 0.06808(1) 0.88

1133.72456 0.07493(1) 0.68

1133.97863 0.07136(2) 0.77

1134.02880 0.07034(1) 0.76

1134.25147 0.08347(5)

1134.45383 0.06720(1)

1134.50970 0.07422(1)

Voigt profile

Air Pressure ShiftTemperature dependence:

Determination of air and air at 240 K

→ nair and nair

Temperature regulated cell

HITRAN [cm-1]

air

[cm-1atm-1](This work)

air

[cm-1atm-1](Smith)

’ 105

[cm-1atm-1 K-

1](This work)

’ 105

[cm-1atm-1 K-1](Smith)

1132.59927

1132.60340

1132.65698 -0.0017(1) 1.8

1132.78600 -0.0010(1)

1132.81144 -0.0004(1)

1133.43351 -0.0014(1) 1.2

1133.58691 -0.0004(7) -2.8(10)

1133.63170 -0.0002(1) 0.0007(2) 0.5(3)

1133.67120 -0.0011(1) -0.0012(1) 1.4 0.4(2)

1133.72456 -0.0005(1) -0.0012(2) -0.6(3)

1133.97863 -0.0004(1) -0.0002(3) 0.1(6)

1134.02880 -0.0016(1) -0.0009(1) 0.6(2)

1134.25147 -0.0018(2) -0.0009(3) -0.4(4)

1134.45383 -0.0004(1) -0.0008(1) 1.7(2)

1134.50970 0.0005(2) 3.3(4)

Smith M. A. H., Malati Devi V., Benner D. C., Rinsland C. P., J. Mol. Spectrosc.

182 (1997) 239-259.

Conclusion

253 nm UV cross section determination

Our IR measurement are 2.2 % higher than HITRAN 08

3.6% inconsistencies between UV (Hearn) and IR (HITRAN 08) recommended values

Position in agreement with HITRAN 08

Measurement of temperature dependence of air broadening and air shifting.

Laser spectroscopic study of ozone in the 100←000 band for the SWIFT instrument

M. Guinet, C. Janssen, D. Mondelain, C. Camy-PeyretLPMAA, CNRS- UPMC (France)

18/06/2010

Jitter of the Laser diode

3.7

1

0-5 c

m-1

0 200 400 600

0,5

0,6

0,7

0,8

0,9

1,0

B

-1,5

x10-4

-1,0

x10

-4-5

,0x1

0-5

0,0

5,0

x10-5

1,0x

10-4

1,5x

10-4

0

100

200

The line is used like a frequency/amplitude noise converter

SStratospheric WWind IInterferometerFFor TTransport studies (SWIFT)

Stratospheric wind velocity

Doppler effect

Wave number

Inte

nsity

5.10-5 cm-1 13 m.s-1

cvv z

0

v1

Limb view

O3 à 1133,4 cm-l

J. Reid, D. T. Cassidy, and R. T. MenziesLinewidth measurements of tunable diode lasers using heterodyne and etalon techniques November 1982 / Vol. 21, No. 21 / APPLIED OPTICS

Exemple of TDL Line Shape :

Repeatability of the determination of the laser line shape

Set of 32 (on two day) measure in a sealed N2O cell

The intensity, lorentz (210-4 cm-1) , gaussian (410-4 cm-1)

are fit on the spectrum

± 4%lorentz

Inte

nsi

ty

± 9

‰

Parameter SD

intensity 9‰

lorentz

gaussian

4%5%

Source of bias Effect on the intensity mean value ( ± 1.6 ‰)

lorentz fix to it’s mean value

0.7‰

gaussian fix to it’s mean value

0.3 ‰

4% on lorentz

5% on gaussian

3‰

1.5‰

We fit the instrument’s apparatus function like a Voigt profile

‰2,1 2,2 2,3 2,4 2,5 2,6 2,7

5,55

5,60

5,65

5,70

5,75

5,80

Stabilized spectrometer

LaserDiode

UV O3 Generation system

I0

FPN2O

Accuracy (1): Position < 4.10-5 cm-1

Intensity < 1%