1 / 28

Databases of Infrared Molecular  Parameters  for Astronomy 0.7 to 1000 μm (14000 to 10 cm -1 )

Databases of Infrared Molecular  Parameters  for Astronomy 0.7 to 1000 μm (14000 to 10 cm -1 ). . Linda R. Brown Jet Propulsion Laboratory California Institute of Technology Pasadena, CA 91109 linda.brown@jpl.nasa.gov

rigg
Télécharger la présentation

Databases of Infrared Molecular  Parameters  for Astronomy 0.7 to 1000 μm (14000 to 10 cm -1 )

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Databases of Infrared Molecular  Parameters  for Astronomy 0.7 to 1000 μm (14000 to 10 cm-1) . Linda R. Brown Jet Propulsion Laboratory California Institute of Technology Pasadena, CA 91109 linda.brown@jpl.nasa.gov The research at the Jet Propulsion Laboratory (JPL), California Institute of Technology was performed under contracts with the National Aeronautics and Space Administration.

  2. ASTRONOMICAL REMOTE SENSING

  3. Basic transition line parameters: ●Line position (or center frequency) ●Line intensity@ 296 K ●Lower state energy (for temperature dependence) ●Vibrational - rotational quantum assignment Line shape parameters (Voigt) ●Pressure-broadened widths & temperature depend. ●Pressure-induced frequency shifts ●Self-broadened widths Line mixing (limited to CO2; no temp. depend) (Other line shapes: none) ●Continua: collision-induced absorption (CIA) (given as cross section files)

  4. Current Public Databases (via Web)

  5. Can’t find your molecule?Try semi-public customized collections

  6. File Structure of HITRAN Compilation (Java HAWKS) Software and Documentation Level 1 HITRAN (line-transition parameters) IR Cross-sections UV Line Coupling CO2 data Aerosol Refractive Indices Level 2 Data Global Data Files, Tables, and References Line-by-line Cross-sections Supplemental Supplemental Alternate Molecule- by-molecule Level 3

  7. A water transition in 2004 HITRAN:11139.7826043.822E-191.168E+00.0659.4228446.69660.590.0019700 0 0 0 0 07 1 7 6 0 6555243332168510224*15.0 13.0 > 4 good < 3 bad 0 = old (1986)

  8. CDMS main page "www.cdms.de"

  9. Properties of the CDMS Catalog • (Mostly) rotational transitions of species for astrophysics and astrochemistry • Molecules detected or detectable in inter/circumstellar medium • Emphasis on Submillimeter and TeraHertz regions • Predictions based on modeling experimental frequencies via Hamiltonians • Separate entries for rarer isotopomers or excited vibrational states (1-1) • Recent entries include • – light hydrides and deuterated species: HD2+, NH, ND, CH2D+, NH2D, NHD2, ND3 • – molecules in excited vibrational states: HCN, HNC, HC3N, HC5N, CS, SiO • – complex species: ethylene glycol • > 300 entries as of April 2005 • Format identical to that of JPL catalog Holger Muller: private communication

  10. CDMS: SELECTED ENTRIESout of 300 species

  11. MASTER: Millimeterwave Acquisitions for Stratospheric/Tropospheric Exchange Research Initial Source of Line Parameters Positions: JPL (almost always) Intensities: JPL or HITRAN or new calculations line broadening: literature or new measurements or HITRAN line shift:literature or new measurements + Interfering species Target molecules H2O O3 HNO3O2N2OHCl CO CH3Cl ClO BrO HOCL HOBr COF2H2O2HO2 H2CO OCSSO2NO2 HCN

  12. Line-by-line parameters should be COMPLETE and ACCURATE (ENOUGH) ACCURACIES REQUIRED FOR MANY APPLICATIONS νPositions & δpressure-induced shifts: 0.000001 - 1.0 cm-1 SLine intensities: 1 to 10% E″ Lower states energies:  ½% γPressure-broadening widths: 1 to 20 % ηTemperature dependence of widths: 10 to 40%

  13. METHODS TO OBTAIN SPECTROSCOPIC PARAMETERS ●Calculations based on successful theoretical modeling (good for positions and intensities, but not line shapes) ●Predictions based on limited data and/or poorer theoretical modeling (warning: extrapolations very poor!) ●Empirical data retrieved line-by-line with some known assignments (warning: no weak lines, larger uncertainties!) ●Absorption cross sections from lab spectra, sometimes at different temperatures (for unresolved heavy species and continua)

  14. Near-IR (0.7 – 2.5 μm) Parameters for earth

  15. Near-IR Methane Positions and Intensities:Difficult to model because energy levels perturb each other. Triacontad: intractable: Cross sections or empirical linelist with 1% assignments. Icosad: almost intractable, but one strong band being studied. Tetradecad: region largely unassigned; no public prediction. Empirical linelist has strongest lines. Octad: poorer prediction overwritten by some empirical results for main isotope. Pentad fundamentals and overtones modeled in 3 isotopes; Hot bands intensities are estimated. Dyad and CH3D fundamentals good. Hot bands intensities modeled to 8%. GS predicted using measured frequencies. Intensities are uncertain and not validated! cm-1

  16. Far-IR CH4 Intensities for ground state transitions in HITRAN and GEISA low by 16%? HITRAN intensities for Far IR set by one “indirect method”, (calc.) [Hilico et al., J Mol Spec, 122, 381(1987)] with claim of accuracy of ± 30%. Cassam-Chenai, [JQSRT, 82,251(2003)] predicts ab initio Q branch based on Stark measurements [Ozier et al. Phys Rev Lett, 27,1329, (1971)]. The intensities are 16% higher than HITRAN values. Lab data (left) confirms a higher value for R branch manifolds. hitran fit from Orton Lab Spectra of Far-IR CH4 (Wishnow)

  17. HITRAN 2004 Far-IR Water Positions (frequencies) well-studied

  18. H2O Line Intensities All isotopologues important but not validated

  19. Warnng! Warning!Far-IR Water Intensities are not measured IsotopeIntensity accuracy and source 11 139.782604 3.822E-19 1.168E+00.0659.4228 446.69660.590.001970 0 0 0 0 0 0 7 1 7 6 0 6 55524333216851 224 15.0 13.0 13 139.997467 1.344E-22 6.538E-01.0919.4389 275.13050.690.004310 0 0 0 0 0 0 5 2 4 4 1 3 50524334226851 224 66.0 54.0 15 140.235360 8.173E-27 1.485E-01.0668.3300 801.35910.490.000000 0 0 0 0 0 0 9 4 6 8 4 5 50554032227 5 2 0 114.0 102.0 14 140.252640 1.725E-24 1.225E-01.0648.3080 942.53220.490.000000 0 0 0 0 0 0 9 5 5 8 5 4 405540 02227 5 2 0 114.0 102.0 12 140.709305 1.269E-24 7.733E-01.0643.2600 1990.85690.41-.010400 0 0 0 0 0 0 11 6 5 11 5 6 40324334222951 2 8 69.0 69.0

  20. Pressure Broadening Pressure-broadened Widths (HWHM) are independent of vibration in some molecules. 1-0 2-0 3-0 Coefficients for these widths temperature dependence also are independent of vibration. Pressured-induced frequency shifts depend on vibration (or position): larger magnitude in Near-IR 1-0 2-0 3-0

  21. Variation of widths by vibrational quanta Methods a. Predict from the Complex Robert-Bonamy equations. b. Estimate widths vs quanta by applying the expected theoretical vibrational dependence to empirical widths at different wavelengths. Left: The estimation method is applied to air-broadened widths of H2O. □ HITRAN 2000 widths ▲Measured widths

  22. Self-broadened CH4 widths in near-IR bandsWidths vary as a function of quanta and band. ν1+ν4 at 4220 cm-1: Widths like those of a 3-fold degenerate (F2) fundamental. These widths are within 4% of ν3 values (at 3020 cm-1) and other bands with a 3-fold vibrational symmetry (F2). ν3+ν4 at 4310 cm-1: 9-fold degenerate band: variation of widths at each J is much greater. ν2+ν3 at 4530 cm-1: 6-fold degenerate band: some variation of widths at each J. Predoi-Cross et al.Multispectrum analysis of 12CH4 from 4100 to 4635 cm-1: 1. self-broadening coefficients (widths and shifts) – in press J. Mol. Spectrosc.

  23. Line mixing (line coupling) in water Top: observed-calculated residuals with line mixing • Eight laboratory spectra of water at 6 μm fitted together in order to retrieve the line positions, intensities and line shape coefficients. • The maximum pressure of hydrogen is 1.3 bar at 296 K. Middle:observed-calculated residuals without line mixing Bottom:H2-Broadened H2O spectra of two pairs of P and R branch transitionsat 1539.5 and 1653 cm-1 in the ν2 band

  24. Line shape study of pure CO (2 – band)Residuals differences between observed and synthetic spectra are offset by -0.1 and -0.2 (Brault et al. 2003).sdVoigt: speed-dependent Voigt profile with line mixing.sVoigt : speed-dependent “ “ without line mixing.

  25. Line mixing observed in CO2 in P and R branches Top: observed-calculated differences between observed and synthetic spectra for 8 lab scans without line mixing Middle:observed-calculated residuals with line mixing between P and R branch lines Bottom:Eight lab spectra ofself-Broadened CO2 in the near –IR. Resolution: 0.011 cm-1. Signal to noise: 2000:1. Max. pressure: 1.3 bar (at 296K).

  26. Models for Collision-Induced Continua • http://www.astro.ku.dk/~aborysow/programs/ A. Borysow, L. Frommhold calculate collision-induced spectra at different temperatures and then form model spectra of cross sections. • Very useful models and software available for generating synthetic spectra H2-H2, H2-He, H2-CH4, H2-Ar, N2-N2, CH4-CH4, N2-CH4, CH4-Ar, CO2-CO2

  27. Low temperature spectrum of methane absorption coefficient= -ln(transmission)/(density^2 * path) Centrifugal distortion dipole lines superposed on collision-induced spectrum. First observation of R(3)-R(7) lines measurements at 0.24 and 0.06 cm-1 spectral resolution Wishnow, Leung, Gush, Rev. Sci. Inst., 70, 23 (1999) Dashed line: CH4Collision-Induced Absorption (CIA) from A. Borysow.

  28. CONCLUSIONS • No public infrared database tailored for astronomy • Astronomers use their own private (undocumented) collections • Basicmolecular parameters (positions, intensities) available for dozens, not hundreds, of species • Near – IR: parameters missing and inaccurate • Far-IR Insufficient attention to line-by-line intensities • Pressure broadening coefficients needed (models and meas.) • CIA models need to be validated.

More Related