66th Ohio State University Symposium on Molecular Spectroscopy June 20–24, 2011 HIGH RESOLUTION SPECTROSCOPY AND GLOBAL ANALYSIS OF THE TETRADECAD REGION

66th Ohio State University Symposium on Molecular Spectroscopy • June 20–24, 2011

HIGH RESOLUTION SPECTROSCOPY AND GLOBAL ANALYSIS OF THE

TETRADECAD REGION OFMETHANE 12CH4

A. NIKITIN,Institute of Atmospheric Optics, 634055 Tomsk, Russia and Laboratoire GSMA, UMR 6089 CNRS-Universit´e de Reims Champagne Ardenne, Moulin de la Housse BP 1039, Cases 16-17, F-51687 Reims Cedex 2, France;

V. BOUDON, C. WENGER,Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS-Universit´e de Bourgogne, 9. Av. A. Savary, BP 47870, F-21078 Dijon Cedex, France;

L. R. BROWN,Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA;

S. BAUERECKER,Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland and Institut für Physikalische und Theoretische Chemie, Technische Universität Braunschweig, D-38106, Germany;

S. ALBERT, M. QUACK,Physical Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland.


Contents

I. The polyads of CH4

II. Analysis of line positions

III. Analysis of line intensities

IV. Conclusions and perspectives


I. The polyads of methane


The polyads of methane

Glo

bal

fit


The Tetradecad vibrational sublevels


Tensorial formalism

Systematic expansion of effective Hamiltonian and transition moment up to any order and for any polyad scheme, thanks to group theory and tensorial methods

All interactions are automatically included

Vibrational extrapolation

Global analyses

H Pk{ }

= t s{ } s'{ }Ω K ,nΓ( )ΓvΓv'β RΩ K ,nΓ( ) ⊗ εV s{ } s'{ }

ΓvΓv' Γ( )⎡⎣ ⎤⎦all indexes∑ (A1g )

Parameters Rotation Vibration


II. Analysis of line positions


Tetradecad analysis

•Starting point: 0–4800 cm-1 global analysis up to Octad: Albert et al., Chem. Phys. 356, 131–146 (2009) and HITRAN 2008

• Improved analysis (although still preliminary) by Andrei Nikitin with MIRS

•Parameter translation to STDS

•STDS improvements (fit procedure, higher order vibrational terms included)

•Global fit: 0 – 6200 cm-1 with STDS

•Paper to be submitted


Fit details

H GS{ } , H Dyad{ } , H Pentad{ } , H Octad{ } , H Tetradecad{ } expanded to order 6, 6, 5, 5, 5, respectively

Total: 19747 data (MW, IR, Raman)

dRMSTetradecad = 23×10−3 cm−1

Number of parameters, ( ) = fitted

Order H GS{ }Tetradecad H Dyad{ }

Tetradecad H Pentad{ }Tetradecad H Octad{ }

Tetradecad H Tetradecad{ }Tetradecad H Tetradecad

0 1 (1) 2 (2) 2 (2) 0 (0) 0 (0) 5 (5)1 0 (0) 2 (2) 5 (5) 0 (0) 0 (0) 7 (7)2 2 (2) 6 (6) 21 (20) 13 (9) 7 (7) 49 (44)3 0 (0) 6 (6) 35 (35) 57 (48) 36 (29) 134 (118)4 3 (3) 13 (13) 71 (65) 183 (147) 219 (113) 489 (341)5 0 (0) 11 (9) 94 (82) 342 (274) 672 (113) 1120 (484)6 4 (4) 22 (20) 0 (0) 0 (0) 0 (0) 26 (24)

Total 10 (10) 62 (53) 228 (209) 596 (478) 896 (747) 1830 (1023)


Residuals for line positions

The octad is slightly worse than in Albert et al.(but still OK)


Residuals for line positions


Calculated levels and mixings


Observed levels and mixings


III. Analysis of line intensities


Octad test


Residuals for line intensities


Global comparison at 296 K


Global comparison at 80 K


Comparison for 4ν4 at 296 K


Comparison for 4ν4 at 78 K


IV. Conclusions and perspectives


CH4 Spectroscopy: what next?

• Continue the « global fit » approach

• Tetradecad much better but still to improve

• Add new data (positions, intensities, hot bands)

• Icosad, …

• CH4 “windows” (high J, far wings)

• Hot methane (combustions, brown dwarfs, hot jupiters, …)

Titan / Cassini-Huygens Huygens DISR spectra Brown dwarf Gliese 229 B / HST


Virtual Atomic and Molecular Data Centerhttp://vamdc.icb.cnrs.fr/PHP/methane.php

Documents

66th Ohio State University Symposium on Molecular Spectroscopy June 20–24, 2011 HIGH RESOLUTION SPECTROSCOPY AND GLOBAL ANALYSIS OF THE TETRADECAD REGION