Spectroscopy Photoelectron spectroscopy X-ray absorption spectroscopy.
SOIR Data Workshop: Spectroscopy SOIR Spectroscopy A.C. Vandaele, R. Drummond, A. Mahieux, S....
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Transcript of 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