Waterloo_01

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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_at_jpl.nas
a.gov The research at the Jet Propulsion
Laboratory (JPL), California Institute of
Technology was performed under contracts with the
National Aeronautics and Space Administration.
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ASTRONOMICAL REMOTE SENSING




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Basic transition line parameters ? Line position
(or center frequency) ? Line intensity _at_ 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)
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Current Public Databases (via Web)
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Cant find your molecule?Try semi-public
customized collections
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File Structure of HITRAN Compilation
(Java HAWKS) Software and Documentation
Level 1
IR Cross-sections
HITRAN (line-transition parameters)
UV
Aerosol Refractive Indices
Line Coupling
CO2 data
Level 2 Data
Global Data Files, Tables, and References
Line-by-line
Cross-sections
Supplemental
Supplemental
Alternate
Molecule- by-molecule
Level 3
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A water transition in 2004 HITRAN11 139.782604
3.822E-19 1.168E00.0659.4228 446.69660.590.00197
0 0 0 0 0 0 0 7 1 7
6 0 6 555243332168510224 15.0 13.0
gt 4 good lt 3 bad 0 old (1986)
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CDMS main page
"www.cdms.de"
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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

• gt 300 entries as of April 2005

• Format identical to that of JPL catalog

Holger Muller private communication
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CDMS SELECTED ENTRIESout of 300 species
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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 HNO3 O2 N2O HCl CO
CH3Cl ClO BrO
HOCL HOBr COF2 H2O2 HO2 H2CO
OCS SO2 NO2 HCN
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Line-by-line parameters should be COMPLETE
and ACCURATE (ENOUGH)

• ACCURACIES REQUIRED FOR MANY APPLICATIONS
• ? Positions d pressure-induced
  shifts 0.000001 - 1.0 cm-1
• S Line intensities 1 to 10
• E? Lower states energies ? ½
• ? Pressure-broadening widths 1 to 20
  
• ? Temperature dependence of widths 10
  to 40

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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)
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Near-IR (0.7 2.5 µm) Parameters for earth
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Near-IR Methane Positions and IntensitiesDiffic
ult 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
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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)
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HITRAN 2004 Far-IR Water Positions (frequencies)
well-studied
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H2O Line Intensities All isotopologues important
but not validated
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Warnng! Warning!Far-IR Water Intensities are not
measured

• Isotope Intensity
  accuracy and source
• 11 139.782604 3.822E-19 1.168E00.0659.4228
  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

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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
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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
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Self-broadened CH4 widths in near-IR bandsWidths
vary as a function of quanta and band.
?1?4 at 4220 cm-1 Widths like those of a
3-fold degenerate (F2) fundamental. These widths
are within 4 of ?3 values (at 3020 cm-1) and
other bands with a 3-fold vibrational symmetry
(F2). ?3?4 at 4310 cm-1 9-fold degenerate
band variation of widths at each J is much
greater. ?2?3 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.
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Line mixing (line coupling) in water
Top observed-calculated residuals with line
mixing
Middle observed-calculated residuals without
line mixing
Bottom H2-Broadened H2O spectra of two pairs of
P and R branch transitions at 1539.5 and 1653
cm-1 in the ?2 band

• 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.

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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.
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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 of self-Broadened CO2
in the near IR. Resolution 0.011 cm-1. Signal
to noise 20001. Max. pressure 1.3 bar (at
296K).
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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

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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 CH4 Collision-Induced Absorption
(CIA) from
A. Borysow.
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CONCLUSIONS

• No public infrared database tailored for
  astronomy
• Astronomers use their own private (undocumented)
  collections
• Basic molecular 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.