9th Biennal HITRAN Conference Harvard-Smithsonian Center for Astrophysics June 26–28, 2006 GLOBAL...

9th Biennal HITRAN Conference • Harvard-Smithsonian Center for Astrophysics • June 26–28, 2006

GLOBAL FREQUENCY AND INFRARED INTENSITY ANALYSIS OF

12CH4 LINES IN THE 0 – 4800 cm-1 REGION

GLOBAL FREQUENCY AND INFRARED INTENSITY ANALYSIS OF

12CH4 LINES IN THE 0 – 4800 cm-1 REGION

Andrei NIKITINLaboratory of Theoretical Spectroscopy, Institute of Atmospheric Optics, Russian Academy of Sciences, 634055 Tomsk, Russia

Vincent BOUDON, Jean-Paul CHAMPION, Michel LOËTELaboratoire 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 QUACKPhysical Chemistry, ETH Zürich, CH-8093 Zürich, SWITZERLAND

Linda R. BROWNJet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA


IntroductionIntroduction• 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, …

Earth Titan Giant planets Brown dwarfs

• Experiments & in situ data far in advance compared to theory !!!


DISR spectrum of Titan (Huygens / ESA)DISR spectrum of Titan (Huygens / ESA)2.0

1.5

1.0

0.5

0.01.61.41.21.00.8

/ Wavelengthμm

12000 10000 9000 8000 7000 6000 / Wavenumber cm-1

= , = 30 Target Sun Altitude km


ContentsContents

I. CH4: Present status and available data

II. The model

III. Fit of line positions

IV. Fit of line intensities

V. Perspectives for CH4 spectroscopy


Present status of CH4 analyses (early 2006)Present status of CH4 analyses (early 2006)

† J.-C. Hilico et al., J. Mol. Spectrosc. 208, 1–13 (2001)

Polyad / Spectral region Line positions Line intensities Line shapes

1 – Ground state

0–200 cm-1 (> 5.0 μm)

Complete analysis,

J ≤ 24Complete analysis No analysis

2 – Dyad

1000–1800 cm-1 (5.6–10.0 μm)

Complete analysis,

J ≤ 23Complete analysis,

with some hot bands

Perturbers:

He et N2

3 – Pentad

2200–3300 cm-1 (3.0–4.6 μm)

Complete analysis,

J ≤ 18Complete analysis,

cold bands only

Perturbers:

He, Ar, N2, O2, CH4

4 – Octad

3700–4800 cm-1 (2.0–2.7 μm)

Perfectible analysis,

J ≤ 16

dRMS = 0.041 cm-1 †

Perfectible analysis, cold bands only

dRMS = 15.6 % †

No analysis

5 – Tetradecad

5400–6300 cm-1 (1.6–1.9 μm)

Incomplete analysis,

J ≤ 10Partial analysis, cold

bands onlyNo analysis

6 – Icosad

6600–7700 cm-1 (1.3 – 1.5 μm)Very partial analysis of 1 band among 20

No analysis No analysis

Upper polyads

> 7800 cm-1 (< 1.28 μm)No analysis No analysis No analysis

Windows

(polyad far wings, all regions)No analysis No analysis No analysis


Available CH4 data used in this workAvailable CH4 data used in this work• Microwave line positions (Zürich, Kiel, Lille)

• Infrared (FTIR) line positions and intensities (KPNO & other sources)

• Raman line positions (Madrid, Dijon)

• 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

NEW !


II. The modelII. The model


The methane moleculeThe methane molecule

Normal modes of methane: ν1 ≈ 2ν 2 ≈ ν 3 ≈ 2ν 4

n =2v1 + v2 + 2v3 + v4Definition of polyad Pn:

S4

C3

Point group: Td

ν1 ν2 ν3 ν4

A1 E F2 F2

Stretching Bending Stretching Bending

Raman Raman IR IR

2916 cm-1 1533 cm-1 3019 cm-1 1311 cm-1

Large rotational constant:


The polyads of CH4The polyads of CH4

G

lob

al f

it


Effective tensorial HamiltonianEffective tensorial Hamiltonian

Systematic tensorial development

Effective Hamiltonian and vibrational extrapolation

ΨrJ ,nC( ) ⊗Ψ v

Cv( )⎡⎣

⎤⎦

Γ( )

Coupled rovibrational basisRotation Vibration

Polyad structure

P0

P1

P2

P3


Vibrational extrapolation examplesVibrational 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


II. Fit of line positionsII. Fit of line positions


Fit detailsFit details

Total: 16 738 data (MW, IR, Raman – 520 new octad lines from ETH)

dRMSDyad = 1.3×10−4 cm−1, dRMS

Pentad = 6.0 ×10−4 cm−1 dRMSOctad = 3.5 ×10−3 cm−1


Fit residuals for line positionsFit residuals for line positions

MW MW MW IR

IR + Raman IR IR IR


Calculated Octad levels and mixings Calculated Octad levels and mixings


Observed Octad levels (Octad – GS) Observed Octad levels (Octad – GS)


Observed Octad levels (Octad – Dyad) Observed Octad levels (Octad – Dyad)


III. Fit of line intensitiesIII. Fit of line intensities


Fit detailsFit details


Fit residuals for line intensitiesFit residuals for line intensities


Dyad intensitiesDyad intensities


Pentad intensitiesPentad intensities


Octad intensitiesOctad intensities


Overview of the new ETH spectrum (78 K)Overview of the new ETH spectrum (78 K)

1.0

0.5

0.04600440042004000

Wavenumber / cm-1

Calc.

Exp.

Resol. = 0.001 cm-1


Comparison with previous results IComparison with previous results I

1.0

0.5

0.0410040904080407040604050

Wavenumber / cm-1

Exp.

New Calc.

Old Calc. (Hilico et al.)


Comparison with previous results IIComparison with previous results II

1.0

0.5

0.04105410441034102410141004099

Wavenumber / cm-1

Exp.

New Calc.

Old Calc. (Hilico et al.)


IV. Perspectives for CH4 spectroscopyIV. Perspectives for CH4 spectroscopy


CH4 spectroscopy: What next ?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


The STDS database

The STDS database

Spherical Top Data System

www.u-bourgogne.fr/LPUB/shTDS.html

• Molecular parameter database

• Calculation and analysis programs

• XTDS : Java interface

9th Biennal HITRAN Conference Harvard-Smithsonian Center for Astrophysics June 26–28, 2006 GLOBAL...

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Transcript of 9th Biennal HITRAN Conference Harvard-Smithsonian Center for Astrophysics June 26–28, 2006 GLOBAL...