SOIR Data Workshop: Spectroscopy SOIR Spectroscopy A.C. Vandaele, R. Drummond, A. Mahieux, S. Robert, V. Wilquet SOIR Belgian Institute for Space Aeronomy (IASB-BIRA)

SOIR Data Workshop: Spectroscopy Overview  Introduction  HITRAN Database  Spectral characteristics  CO 2  CO

SOIR Data Workshop: Spectroscopy Overview  Introduction  HITRAN Database  Spectral characteristics  CO 2  CO

SOIR Data Workshop: Spectroscopy Introduction (1) « Study of the electromagnetic radiation emitted or absorbed by a chemical specie » Detection of molecular species Physical properties (geometry) quantity conditions (temperature, pressure) wavelength Intensity The molecules disassociate The molecules vibrate The molecules rotate

SOIR Data Workshop: Spectroscopy Introduction (2) Ground state E Excited state Vibration

SOIR Data Workshop: Spectroscopy Introduction (3) E E Excited state Ground state J” J’ Vibration - Rotation

SOIR Data Workshop: Spectroscopy CO 2 H2OH2O CO 2 & 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 | | Introduction (5)

SOIR Data Workshop: Spectroscopy Rotational Temperature Introduction (6) Using the absolute intensity, we can obtain the rotational temperature T rot

SOIR Data Workshop: Spectroscopy Overview  Introduction  HITRAN Database  Spectral characteristics  CO 2  CO

SOIR Data Workshop: Spectroscopy HITRAN Database high-resolution transmission molecular absorption database The HITRAN 2008 Database contains 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) (n air ) Pressure shift (Shift air ) Upper vibrational quanta Lower vibrational quanta … Need to be adapted for the CO 2 -rich atmosphere of Venus Literature: Toth and Darnton, JMS 49, (1974) ; Sung & Varanasi, JQSRT 91, (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, (2011)

SOIR Data Workshop: Spectroscopy Overview  Introduction  HITRAN Database  Spectral characteristics  CO 2  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 : cm -1 (4.4 – 2.2 µm)  Main IR absorbing species : H 2 O, CO 2, CO, HCl, …  Temperature range: K  Pressure range: bar  Order addition !

SOIR Data Workshop: Spectroscopy Overview  Introduction  HITRAN Database  Spectral characteristics  CO 2  CO

SOIR Data Workshop: Spectroscopy CO2: isotopologues (1)

SOIR Data Workshop: Spectroscopy CO 2 isotopologues (2) : Diffraction order Wavenumber (cm -1 )

SOIR Data Workshop: Spectroscopy CO 2 isotopologues (3) : Diffraction order 124 CO 2 (628) CO 2 (627)

SOIR Data Workshop: Spectroscopy CO 2 isotopologues (4) : Diffraction order 132 Transmittance Wavenumber (cm -1 ) HCl X SPECIES band of 16 O 12 C 18 O was not present in HITRAN or CDSD Wilquet et al., JQSRT, 109, , 2008

SOIR Data Workshop: Spectroscopy CO 2 (638) & HDO CO 2 isotopologues (5) : Diffraction order 121 R 5e R 29e

SOIR Data Workshop: Spectroscopy Overview  Introduction  HITRAN Database  Spectral characteristics  CO 2  CO

SOIR Data Workshop: Spectroscopy CO isotopologues (1) Orders 188…

SOIR Data Workshop: Spectroscopy CO isotopologues (2) : Diffraction order 191

SOIR Data Workshop: Spectroscopy CO isotopologues (3) : Diffraction order Wavenumber (cm -1 )

SOIR Data Workshop: Spectroscopy Thank you for your attention

SOIR Data Workshop: Spectroscopy