SOIR Spectroscopy A C Vandaele R Drummond A

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

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

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

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

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

Introduction (3) Vibration - Rotation E E Excited state Ground state 4 J’ 3 2 1 0 4 J” 3 2 1 0 Excited state Ground state SOIR Data Workshop: Spectroscopy

Introduction 1 orbit (4) 4 diffraction orders H 2 O CO 2 & HCl CO 2 CO Wavenumber (cm-1) SOIR Data Workshop: Spectroscopy

Introduction (5) A: amplitude nij: line position aij: integrated absorption coefficient g: half width at half maximum (HWHM) or linewidth g=0. 5 |n 1 -n 2| 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 SOIR Data Workshop: Spectroscopy

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

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

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/ Molecule number Isotopologue number Transition wavenumber (cm -1) Line Intensity Einstein A-coefficient Air-broadened width (gair) Self-broadened width (gself) Need to be adapted for the CO 2 -rich atmosphere of Venus Lower-state Energy Temperature dependence (of air width) (nair) Pressure shift (Shiftair) Upper vibrational quanta Lower vibrational quanta … 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 q Introduction q HITRAN Database q Spectral characteristics q CO 2 q CO SOIR Data Workshop: Spectroscopy

Spectral characteristics SOIR characteristics to keep in mind: Ø Spectral resolution : from 0. 12 up to 0. 21 cm-1 Ø Spectral range : 2200 - 4400 cm-1 (4. 4 – 2. 2 µm) Ø Main IR absorbing species : H 2 O, CO 2, CO, HCl, … Ø Temperature range: 100 - 350 K Ø Pressure range: 10 -2 - 10 -8 bar Ø Order addition ! SOIR Data Workshop: Spectroscopy

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

CO 2: isotopologues (1) SOIR Data Workshop: Spectroscopy

CO 2 isotopologues (2) : Diffraction order 149 3330 Wavenumber (cm-1) 3355 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 HCl Transmittance 0 1 1 11 - 0 01 band of 16 O 12 C 18 O was not present in HITRAN or CDSD X SPECIES 2950 Wilquet et al. , JQSRT, 109, 895 -905, 2008 Wavenumber (cm-1) 2975 SOIR Data Workshop: Spectroscopy

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

Overview q Introduction q HITRAN Database q Spectral characteristics q CO 2 q 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

SOIR Data Workshop: Spectroscopy