1. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 GLOBAL FREQUENCY AND INFRARED INTENSITY ANALYSIS OF 12 CH 4 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 LO Ë TE 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 Z ü rich, CH-8093 Z ü rich, SWITZERLAND Linda R. BROWN Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA

2. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Introduction Need for a precise modeling of excited methane states: Earth’s atmosphere, planets (Titan, …), brown dwarfs, … Previous studies of the Octad were not enough accurate: d RMS = 0.041 cm -1 for positions and 15.6 % for intensities (J.-C. Hilico et al., J. Mol. Spectrosc. 208, 1–13 (2001)) Availability of new experimental data: New intensities measured at KPNO New high-resolution spectra recorded at ETH Z ü rich: - Bruker IFS 125 HR Z ü rich Prototype (ZP2001) - Instrumental bandwidth ≤ 0.001 cm -1, unapodized - T = 78 K

3. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Contents I.The model II.Fit of line positions III.Fit of line intensities IV.Perspectives for CH 4 spectroscopy

4. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 I. The model

5. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 The methane molecule Normal modes of methane: Definition of polyad P n : S4S4 C3C3 Point group: T d 1 2 3 4 A1A1 EF2F2 F2F2 StretchingBendingStretchingBending Raman IR 2916 cm -1 1533 cm -1 3019 cm -1 1311 cm -1 Large rotational constant:

6. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 The polyads of CH 4  Global fit 

7. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Effective tensorial Hamiltonian Systematic tensorial development Effective Hamiltonian and vibrational extrapolation Coupled rovibrational basis Rotation Vibration Polyad structure P0P0 P1P1 P2P2 P3P3

8. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Vibrational extrapolation examples 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

9. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 II. Fit of line positions

10. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Fit details

11. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Fit residuals for line positions MW IR IR + Raman IR

12. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Octad levels and mixings

13. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 III. Fit of line intensities

14. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Fit details

15. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Fit residuals for line intensities

16. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Octad intensities

17. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Overview of the new ETH spectrum (78 K) Calc. Exp. Resol. = 0.001 cm -1

18. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Comparison with previous results I Exp. New Calc. Old Calc. (Hilico et al.)

19. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 Comparison with previous results II Exp. New Calc. Old Calc. (Hilico et al.)

20. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 IV. Perspectives for CH 4 spectroscopy

21. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 CH 4 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, …) Titan / Cassini-Huygens Huygens DISR spectraBrown dwarf Gliese 229 B / HST

22. 61th Ohio State University Symposium on Molecular Spectroscopy June 19–23, 2006 The STDS database Spherical Top Data System www.u-bourgogne.fr/LPUB/shTDS.html Molecular parameter database Calculation and analysis programs XTDS : Java interface