1. Jet Propulsion Laboratory California Institute of Technology 1 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 The importance of being earnest about line shapes!! Charles E. Miller and Linda R. Brown Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr., Pasadena, California 91109 Acknowledgments The research at the Jet Propulsion Laboratory (JPL), California Institute of Technology, was performed under contract with National Aeronautics and Space Administration.

2. Jet Propulsion Laboratory California Institute of Technology 2 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 Return global X CO2 data with 0.3% precision Our Research Goal: Improve CO 2 and O 2 line parameters

3. Jet Propulsion Laboratory California Institute of Technology 3 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 Better Accuracies Require Precise Knowledge/Control of the Experimental State Pristine cells – no contamination Temperature monitoring inside the cell Isotopic enriched samples Mass spectrometric standard samples Stable spectrometer performance Goal for Experimental Uncertainties: Abundances:  0.05% (purity, Isotope) Pressure:  0.01 Torr (if P > 10 Torr) Temperature:  0.1 K Path:  2 mm (0.1%) Signal/noise:2000:1 Resolution:nearly Doppler-limited 100% Trans:  0.1% 0% Trans:  0.1% Instrumental line shape Four Temp Probes (PRT) going Inside the Cell

4. Jet Propulsion Laboratory California Institute of Technology 4 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 Molecular Line Shape Problem! Miller et al. Comptes Rendus Physique 6 (2005). Voigt only Strange residuals Strange residuals (!) Multispectrum retrievals one solution for all lines fitting all spectra simultaneously [modified from Benner et al. JQSRT 53, 705 (1995)] NEW CO 2 Lab parameters could not be used in (Voigt only) atmospheric retrievals. non-Voigt line shapes (line mixing + speed dependence + narrowing)

5. Jet Propulsion Laboratory California Institute of Technology 5 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 Too many line shape choices! Lisak et al. 2010 O 2 B-band

6. Jet Propulsion Laboratory California Institute of Technology 6 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 What we have to do now! Learn what combination of line shapes can produce the best atmospheric retrievals. Create and Validate universal software using the required molecular shapes to compute synthetic spectra (radiances etc….). Give standardized software to both atmospheric and lab spectroscopists: So that new lab parameters will be consistent with atmospheric calculations.

7. Jet Propulsion Laboratory California Institute of Technology 7 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 Need to do better lab studies Use community-validated multi-spectrum retrieval codes that permit us to obtain consistent values of line shape parameters. (do intercomparisons) Use gas pressure that can reveal all activated line shapes (Voigt, speed dependence, line mixing, narrowing …..). Excellent instrumental performance (usual stuff). Conventional Strategy: Sequential L-B-L analyses Quantum modeling Pres. (atm) 1 st Positions: < 0.001 2 nd Intensities: < ~ 0.010 To Create good database for broadening retrievals 3 rd Shapes: Lorentz: 0.10 – 1. Narrowing & 0.03 – 0.1 Speed Dependence (Lorentz=Doppler) Line mixing: 0.5 – 10 Collision Induced Abs: 1 – 20 ?

8. Jet Propulsion Laboratory California Institute of Technology 8 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 Constraining multispectrum fits! STRATEGY: Fit all lines and spectra simultaneously BUT Constrain positions and intensities and adjust constants in the quantum mechanical equations (instead of fitting line-by-line) Pressure broadening parameters still fitted line-by-line Line Positions: ν i = ν 0 + B(J(J+1)) - D(J(J+1)) 2 + H(J(J+1)) 3 – E" ν i Resonant frequency ν 0 Band origin J Rotational quantum number E" Lower state rotational energy (fixed) ν 0, B, D, H, upper state constants of each band in the region, are the adjusted instead of individual positions. Line Intensities: S i = ( i / 0 )(S v /L i ) exp(-hcE i ″/kT)[1-exp(hcv i /kT)]F S i,observed individual line intensity S v vibrational band intensity, F Herman-Wallis factor = [1+A 1 m+A 2 m 2 +A 3 m 3 ] 2 L i Hönl-London factor, where l i = (m 2  l″ 2 )/|m| for CO 2 m = J″+1 R branch, m =  J″ for the P branch J″, llower-state rotational & angular momentum quanta Q r lower state rotational partition function at T 0 =296 K E i ″ lower state rotational energy S v, A 1, A 2 are the adjusted parameters Can we do this for asymmetric tops? symmetric tops?

9. Jet Propulsion Laboratory California Institute of Technology 9 V-1 11 th HITRAN Conference, Cambridge, MA, June 16-18, 2010 CALL TO ACTION! Fits to laboratory and atmospheric spectra must use the same line shape formulations Create new universal line shape (LS) software Validate LS formulations Expand databases to include all necessary LS parameters Convince sponsors to fund it! Coming goal: 0.1% accuracy for strongest bands