soir data workshop: spectroscopy soir spectroscopy a.c. vandaele, r. drummond, a. mahieux, s....

SOIR Data Workshop: Spectroscopy

SOIRSpectroscopy

A.C. Vandaele, R. Drummond, A. Mahieux, S. Robert, V. WilquetSOIR Team @ Belgian Institute for Space Aeronomy (IASB-BIRA)

SOIR Data Workshop: Spectroscopy

Overview

Introduction

HITRAN Database

Spectral characteristics

CO2

CO

SOIR Data Workshop: Spectroscopy

Overview

Introduction

HITRAN Database

Spectral characteristics

CO2

CO

SOIR Data Workshop: Spectroscopy

Introduction (1)

« Study of the electromagnetic radiation emitted or absorbed by a chemical specie »

Detection of molecular speciesPhysical properties (geometry)quantityconditions (temperature, pressure)

wavelength

hc

E

Inte

nsi

ty

The molecules disassociate The molecules vibrate The molecules rotate

SOIR Data Workshop: Spectroscopy

Introduction (2)

hc

E

Ground state

E

Excited state

Vibration

SOIR Data Workshop: Spectroscopy

Introduction (3)

E

0123

4

0123

4

E

Excited stateExcited state

Ground state

Ground state

J”

J’

Vibration - Rotation

SOIR Data Workshop: Spectroscopy

CO2

H2OCO2 &HCl

CO

Wavenumber (cm-1)

1 orbit 4 diffraction orders

Introduction (4)

SOIR Data Workshop: Spectroscopy

A spectral line extends over a range of frequencies, not a single frequency:

• Natural broadening: lifetime of the excited state Lorentzian profile

• Pressure broadening & shift: collision with the nearby particles Lorentzian profile

• Thermal Doppler broadening: the higher the temperature of the gas, the wider the distribution of velocities in the gas, the broader will be the spectral line Gaussian profile

Gauss function Lorentz function Voigt profile

A: amplitude

ij: line position

ij: integrated absorption coefficient

: half width at half maximum (HWHM) or linewidth

=0.5 |1-2|

Introduction (5)

SOIR Data Workshop: Spectroscopy

Rotational Temperature

Introduction (6)

rot

i

kT

E

ijiij HLgconstS

exp)(~)(

Using the absolute intensity, we can obtain the rotational temperature Trot

SOIR Data Workshop: Spectroscopy

Overview

Introduction

HITRAN Database

Spectral characteristics

CO2

CO

SOIR Data Workshop: Spectroscopy

HITRAN Database

http://www.cfa.harvard.edu/hitran

http://hitran.iao.ru/

high-resolution transmission molecular absorption database

The HITRAN 2008 Database contains 2 713 968 spectral lines for 39 different molecules.

Molecule number

Isotopologue number

Transition wavenumber (cm-1)

Line Intensity

Einstein A-coefficient

Air-broadened width (air)

Self-broadened width (self)

Lower-state Energy

Temperature dependence (of air width) (nair)

Pressure shift (Shiftair)

Upper vibrational quanta

Lower vibrational quanta

…

Need to be adapted for the CO2-rich atmosphere of Venus

Literature:

Toth and Darnton, JMS 49, 100-105 (1974) ;

Sung & Varanasi, JQSRT 91, 319-322 (2005) ;

L.R. Brown, C.M.Humphrey, R.R. Gamache et al., JMS 246 (2007) ;

R.R. Gamache, A.L. Laraia, J. Lamouroux, Icarus 213, 720-730 (2011)

SOIR Data Workshop: Spectroscopy

Overview

Introduction

HITRAN Database

Spectral characteristics

CO2

CO

SOIR Data Workshop: Spectroscopy

Spectral characteristics

SOIR characteristics to keep in mind:

Spectral resolution : from 0.12 up to 0.21 cm-1

Spectral range : 2200 - 4400 cm-1 (4.4 – 2.2 µm)

Main IR absorbing species : H2O, CO2, CO, HCl, …

Temperature range: 100 - 350K

Pressure range: 10-2 - 10-8 bar

Order addition !

SOIR Data Workshop: Spectroscopy

Overview

Introduction

HITRAN Database

Spectral characteristics

CO2

CO

SOIR Data Workshop: Spectroscopy

CO2: isotopologues (1)

SOIR Data Workshop: Spectroscopy

CO2 isotopologues (2) : Diffraction order 149

3330 3355Wavenumber (cm-1)

SOIR Data Workshop: Spectroscopy

CO2 isotopologues (3) : Diffraction order 124

CO2 (628)

CO2 (627)

SOIR Data Workshop: Spectroscopy

CO2 isotopologues (4) : Diffraction order 132T

ran

smitt

an

ce

Wavenumber (cm-1)

HCl

X SPECIES

2950 2975

0 1 1 11- 0 0 0 01 band of 16O12C18O

was not present in HITRAN or CDSD

Wilquet et al., JQSRT, 109, 895-905, 2008

SOIR Data Workshop: Spectroscopy

CO2(638) & HDO

CO2 isotopologues (5) : Diffraction order 121

R 5

e

R 2

9e

SOIR Data Workshop: Spectroscopy

Overview

Introduction

HITRAN Database

Spectral characteristics

CO2

CO

SOIR Data Workshop: Spectroscopy

CO isotopologues (1)

Orders 188…191

2-0

SOIR Data Workshop: Spectroscopy

CO isotopologues (2) : Diffraction order 191

SOIR Data Workshop: Spectroscopy

CO isotopologues (3) : Diffraction order 185

4140 4165

Wavenumber (cm-1)

SOIR Data Workshop: Spectroscopy

Thank you for your attention

SOIR Data Workshop: Spectroscopy