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 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 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 CO 2 ; no temp. depend) (Other line shapes: none) ● Continua: collision-induced absorption (CIA) (given as cross section files)

4 Current Public Databases (via Web) Database Websites ( Region cm -1 Num of Species Num of Transitions HITRAN 2004 cfa - (/hitran) terrestrial moleculeswww.harvard.edu 0.0 to ,734,469 GEISA 2003 ara.lmd.polytechnique.fr molecules planetary  terrestrial 0.0 to (98 iso) 1,668,371 JPL 2005 spec.jpl.nasa.gov spec.jpl.nasa.gov molecules,radicals,atoms astrophysics  terrestrial 0.0 to 100. (1314.) (340) 2,644,111 CMSD 2005 (Cologne) molecules,radicals,atoms astrophysics 0. to 300. (1134.) (300) 2 M?

5 Can’t find your molecule? Try semi-public customized collections DatabaseswebsitesRegion cm -1. Number of species Number of transitions PNNL Air pollution nwir.pnl.gov Cross sections only ($200) VPL Astrobiology vpl.ipac.caltech.edu vpl.ipac.caltech.edu /spectra/ – PNNL, HITRAN, ( team only) CDSD (CO 2 ) ftp://ftp.iao.ru/pub/ 0 – (CO 2 ) at 296K, 1000K Predictions based on modeled data custom SAO, HITEMP, ATMOS ….. Infrared - astronomy NONE 10 to 14000

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

7 A water transition in 2004 HITRAN: E E * Parameter Field size Definition MolI2Molecule number IsoI1Isotope number (1 = most abundant, 2 = 2nd most abundant,..) ν if F12.6Transition position in vacuum [cm -1 ] S if E10.3Intensity [cm -1 /(molecule∙cm K] A if E10.3Einstein A-coefficient [s -1 ] γ air F5.4Air-broadened half-width (HWHM) [cm K] γ self F5.4Self-broadened half-width (HWHM) [cm K] E″F10.4Lower-state energy [cm -1 ] n air F4.2Temperature-dependence coefficient of air width δ air F8.6Air pressure-induced shift [cm K] v′, v″2A15Upper and Lower “global” quantum numbers q′, q″2A15Upper and Lower “local” quantum numbers ierr6I1Uncertainty indices for ν if, S if, γ air, γ self, n air, δ air iref6I2Reference pointers for ν if, S if, γ air, γ self, n air, δ air * A1Flag for line-coupling algorithm (line mixing) g′, g″2F7.1Upper and Lower statistical weights > 4 good < 3 bad 0 = old (1986)

8 CDMS main page "

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: HD 2 +, NH, ND, CH 2 D +, NH 2 D, NHD 2, ND 3 – molecules in excited vibrational states: HCN, HNC, HC 3 N, HC 5 N, CS, SiO – complex species: ethylene glycol  Format identical to that of JPL catalog Holger Muller: private communication  > 300 entries as of April 2005

10 CDMS: SELECTED ENTRIES out of 300 species CDMS: SELECTED ENTRIES out of 300 species

11 MASTER: Millimeterwave Acquisitions for Stratospheric/Tropospheric Exchange Research Target molecules HOCL HOBr COF 2 H 2 O 2 HO 2 H 2 CO OCS SO 2 NO 2 HCN H2O O3 HNO3 O 2 N2O HCl CO CH3Cl ClO BrO + Interfering species 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

12 Line-by-line parameters should be COMPLETE and ACCURATE (ENOUGH) ACCURACIES REQUIRED FOR MANY APPLICATIONS ν Positions & δ pressure-induced shifts: cm -1 S Line intensities:1 to 10% E″ Lower states energies:  ½% γ Pressure-broadening widths: 1 to 20 % η Temperature 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 SPECIES (HITRAN#) GENERAL COMMENT STATUS OF HITRAN 2000/04 CO (5)BEST CASE Complete Better intensities and broadening available N 2 O (4)BEST CASE Almost complete ( a few bands missing ) CO 2 (2) GOOD Better accuracies needed; line shape?? Almost complete intensities and positions often inaccurate O 2 (7) FAIR Models good; too much scatter in lab measurements; line shape?? Almost complete intensities and pressure broadening uncertain H 2 O (1) FAIR Hamiltonian models fail in NIR; empirical linelists available Incomplete weak lines missing; some better accuracies needed O 3 (3) FAIR Theory may work well enough; some measurements exists Incomplete atmospheric bands missing at 2.2 μm CH 4 (6)WORST CASE No Models for NIR; very few measurements available Incomplete Missing bands: Few assignments (no E″)

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 CH 3 D fundamentals good. Hot bands intensities modeled to 8%. GS predicted using measured frequencies. Intensities are uncertain and not validated! cm -1

16 Far-IR CH 4 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. Lab Spectra of Far-IR CH4 (Wishnow) hitran fit from Orton

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

18 H 2 O Line Intensities All isotopologues important but not validated

19 Warnng! Warning! Far-IR Water Intensities are not measured Isotope Intensity accuracy and source E E E E E E E E E E

20 Pressure-broadened Widths ( HWHM ) are independent of vibration in some molecules. 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 Pressure Broadening

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 H 2 O. □ HITRAN 2000 widths ▲Measured widths

22 Self-broadened CH 4 widths in near-IR bands Self-broadened CH 4 widths in near-IR bands Widths vary as a function of quanta and band. ν 1 +ν 4 at 4220 cm -1 : Widths like those of a 3-fold degenerate (F2) fundamental. These widths are within 4% of ν 3 values (at 3020 cm -1 ) and other bands with a 3- fold vibrational symmetry (F2). ν 3 +ν 4 at 4310 cm -1 : 9-fold degenerate band: variation of widths at each J is much greater. ν 2 +ν 3 at 4530 cm -1 : 6-fold degenerate band: some variation of widths at each J. Predoi-Cross et al. Multispectrum analysis of 12 CH 4 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 u Eight laboratory spectra of water at 6 μm fitted together in order to retrieve the line positions, intensities and line shape coefficients. u The maximum pressure of hydrogen is 1.3 bar at 296 K. Top: observed-calculated residuals with line mixing Middle: observed-calculated residuals without line mixing Bottom: H 2 -Broadened H 2 O spectra of two pairs of P and R branch transitions at and 1653 cm -1 in the ν 2 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. 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 CO 2 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 of self- Broadened CO 2 in the near –IR. Resolution: cm -1. Signal to noise: 2000:1. Max. pressure: 1.3 bar (at 296K).

26 Models for Collision-Induced Continua u A. Borysow, L. Frommhold calculate collision-induced spectra at different temperatures and then form model spectra of cross sections. u Very useful models and software available for generating synthetic spectra H 2 -H 2, H 2 -He, H 2 -CH 4, H 2 -Ar, N 2 -N 2, CH 4 -CH 4, N 2 -CH 4, CH 4 -Ar, CO 2 -CO 2

27 Low temperature spectrum of methane absorption coefficient= -ln(transmission)/(density^2 * path) First observation of R(3)-R(7) lines measurements at 0.24 and 0.06 cm-1 spectral resolution Centrifugal distortion dipole lines superposed on collision-induced spectrum. Dashed line: CH 4 Collision-Induced Absorption (CIA) from A. Borysow. Wishnow, Leung, Gush, Rev. Sci. Inst., 70, 23 (1999)

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