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SOIR Spectroscopy
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  1. SOIRSpectroscopy A.C. Vandaele, R. Drummond, A. Mahieux, S. Robert, V. Wilquet SOIR Team @ Belgian Institute for Space Aeronomy (IASB-BIRA)

  2. Overview • Introduction • HITRAN Database • Spectral characteristics • CO2 • CO

  3. Overview • Introduction • HITRAN Database • Spectral characteristics • CO2 • CO

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

  5. Introduction (2) Vibration E Excited state l Ground state

  6. 4 4 3 3 2 2 1 1 0 0 Introduction (3) Vibration - Rotation E E Excited state J’ Excited state J” Ground state Ground state

  7. Introduction (4) 1 orbit  4 diffraction orders CO2 & HCl H2O CO2 CO Wavenumber (cm-1)

  8. Introduction (5) A: amplitude nij: line position aij: integrated absorption coefficient g: half width at half maximum (HWHM) or linewidth g=0.5 |n1-n2| • 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

  9. Introduction (6) Rotational Temperature Using the absolute intensity, we can obtain the rotational temperature Trot

  10. Overview • Introduction • HITRAN Database • Spectral characteristics • CO2 • CO

  11. HITRAN Database • high-resolution transmission molecular absorption database • The HITRAN 2008 Database contains 2 713 968 spectral lines for 39 different molecules. http://www.cfa.harvard.edu/hitran http://hitran.iao.ru/ 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)

  12. Overview • Introduction • HITRAN Database • Spectral characteristics • CO2 • CO

  13. ! 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

  14. Overview • Introduction • HITRAN Database • Spectral characteristics • CO2 • CO

  15. CO2: isotopologues (1)

  16. CO2 isotopologues (2) : Diffraction order 149 3355 3330 Wavenumber (cm-1)

  17. CO2 isotopologues (3) : Diffraction order 124 CO2 (628) CO2 (627)

  18. HCl Transmittance X SPECIES Wavenumber (cm-1) CO2 isotopologues (4) : Diffraction order 132 0 1 1 11- 0 0 0 01 band of 16O12C18O was not present in HITRAN or CDSD 2950 2975 Wilquet et al., JQSRT, 109, 895-905, 2008

  19. CO2 isotopologues (5) : Diffraction order 121 CO2(638) & HDO R 29e R 5e

  20. Overview • Introduction • HITRAN Database • Spectral characteristics • CO2 • CO

  21. Orders 188…191 CO isotopologues (1) 2-0

  22. CO isotopologues (2): Diffraction order 191

  23. CO isotopologues (3): Diffraction order 185 4140 4165 Wavenumber (cm-1)

  24. Thank you for your attention