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Andrei NIKITIN

GLOBAL FREQUENCY AND INFRARED INTENSITY ANALYSIS OF 12 CH 4 LINES IN THE 0 – 4 800 cm -1 REGION. Andrei NIKITIN Laboratory of Theoretical Spectroscopy, Institute of Atmospheric Optics, Russian Academy of Sciences, 634055 Tomsk, Russia Vincent BOUDON , Jean-Paul CHAMPION, Michel LO Ë TE

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Andrei NIKITIN

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  1. GLOBAL FREQUENCY AND INFRARED INTENSITY ANALYSIS OF 12CH4 LINES IN THE 0 – 4800 cm-1 REGION Andrei NIKITIN Laboratory of Theoretical Spectroscopy, Institute of Atmospheric Optics, Russian Academy of Sciences, 634055 Tomsk, Russia Vincent BOUDON, Jean-Paul CHAMPION, Michel LOËTE Laboratoire de Physique de l’Université de Bourgogne – CNRS UMR 5027, 9 Av. A. Savary, BP 47870, F-21078 DIJON, FRANCE Sieghard ALBERT, Sigurd BAUERECKER, Martin QUACK Physical Chemistry, ETH Zürich, CH-8093 Zürich, SWITZERLAND Linda R. BROWN Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA

  2. Earth Titan Giant planets Brown dwarfs • CH4 is an important greenhouse gas and a major constituent of planetary atmospheres • Need for a precise modeling of excited methane states: Earth’s atmosphere, planets (Titan, …), brown dwarfs, … Introduction • Experiments & in situ data far in advance compared to theory !!!

  3. DISR spectrum of Titan (Huygens / ESA)

  4. Contents • CH4: Present status and available data • The model • Fit of line positions • Fit of line intensities • Perspectives for CH4 spectroscopy

  5. I. CH4: Present status and available data

  6. Present status of CH4 analyses (early 2006) † J.-C. Hilico et al., J. Mol. Spectrosc. 208, 1–13 (2001)

  7. NEW ! • Availability of new experimental data (2005–2006): • New intensities measured at KPNO • New high-resolution spectra recorded at ETH Zürich: - Bruker IFS 125 HR Zürich Prototype (ZP2001) - Instrumental bandwidth ≤ 0.001 cm-1, unapodized - T = 78 K • Microwave line positions (Zürich, Kiel, Lille) • Infrared (FTIR) line positions and intensities (KPNO & other sources) • Raman line positions (Madrid, Dijon) Available CH4 data used in this work

  8. II. The model

  9. S4 C3 Point group: Td Definition of polyad Pn: Large rotational constant: The methane molecule Normal modes of methane:

  10.  Global fit  The polyads of CH4

  11. Polyad structure P3 • Systematic tensorial development Vibration Rotation P2 • Coupled rovibrational basis P1 • Effective Hamiltonian and vibrational extrapolation P0 Effective tensorial Hamiltonian

  12. • Effective Hamiltonian for the Octad:  Simultaneous fit of GS, Dyad, Pentad and Octad • Effective dipole moment for Pentad–Dyad transitions:  Simultaneous fit of Dyad–GS and Pentad–Dyad intensities Vibrational extrapolation examples

  13. II. Fit of line positions

  14. Fit details

  15. Fit residuals for line positions MW MW IR MW IR + Raman IR IR IR

  16. Calculated Octad levels and mixings

  17. Observed Octad levels (Octad – GS)

  18. Observed Octad levels (Octad – Dyad)

  19. III. Fit of line intensities

  20. Fit details

  21. Fit residuals for line intensities

  22. Dyad intensities

  23. Pentad intensities

  24. Octad intensities

  25. Overview of the new ETH spectrum (78 K) Calc. Exp. Resol. = 0.001 cm-1

  26. Comparison with previous results I Old Calc. (Hilico et al.) New Calc. Exp.

  27. Comparison with previous results II Old Calc. (Hilico et al.) New Calc. Exp.

  28. IV. Perspectives for CH4 spectroscopy

  29. CH4 spectroscopy: What next ? • Continue the global fit approach • Next step: the Tetradecad (5400 – 6300 cm-1) • Add new data (positions & intensities, cold & hot bands) • Icosad, … • Methane windows (high-J, far wings) for planetary atmospheres • Hot methane (combustions, brown dwarfs, …) • Isotopologues: 13CH4, 12CH3D, … • HITRAN update with the new results

  30. The STDS database Spherical Top Data System www.u-bourgogne.fr/LPUB/shTDS.html • Molecular parameter database • Calculation and analysis programs • XTDS : Java interface

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