95 research outputs found
HITRAN2016: Part I. Line lists for H2O, CO2, O3, N2O, CO, CH4, and O2
The HITRAN2016footnote{I. E. Gordon, L. S. Rothman, C. Hill, R. V. Kochanov, Y. Tan, et al. The HITRAN2016 Molecular Spectroscopic Database. JQSRT 2017;submitted.} database is now officially releasedfootnote{Many spectroscopists and atmospheric scientists worldwide have contributed data to the database or provided invaluable validations.}._x000d_
Plethora of experimental and theoretical molecular spectroscopic data were collected, evaluated and vetted before compiling the new edition of the database. The database is now distributed through the dynamic user interface HITRAN (available at underline{www.hitran.org}) which offers many flexible options for browsing and downloading the datafootnote{C. Hill, I. E. Gordon, R. V. Kochanov, L. Barrett, J.S. Wilzewski, L.S. Rothman, JQSRT. 177 (2016) 4-β14}. In addition HITRAN Application Programming Interface (HAPI) offers modern ways to download the HITRAN data and use it to carry out sophisticated calculationsfootnote{R.V. Kochanov, I. E. Gordon, L. S. Rothman, P. Wcislo, C. Hill, J. S. Wilzewski, JQSRT. 177 (2016) 15β-30.}._x000d_
The line-by-line lists for almost all of the 47 HITRAN molecules were updated in comparison with the previous compilation (HITRAN2012footnote{L. S. Rothman, I. E. Gordon et al. The HITRAN2012 Molecular Spectroscopic Database. JQSRT, 113 (2013) 4--50.}). Some of the most important updates for major atmospheric absorbers, such as HO, CO, O, NO, CO, CH, and O, will be presented in this talk, while the trace gases will be presented in the next talk by Y. Tan. The HITRAN2016 database now provides alternative line-shape representations for a number of molecules, as well as broadening by gases dominant in planetary atmospheres. In addition, substantial extension and improvement of cross-section data is featured, which will be described in a dedicated talk by R. V.~Kochanov._x000d_
The new edition of the database is a substantial step forward to improve retrievals of the planetary atmospheric constituents in comparison with previous editions, while offering new ways of working with the data.\_x000d_
The HITRAN database is supported by the NASA AURA and PDART program grants NNX14AI55G and NNX16AG51G
Referencing Sources of Molecular Spectroscopic Data in the Era of Data Science: Application to the HITRAN and AMBDAS Databases
The application described has been designed to create bibliographic entries
in large databases with diverse sources automatically, which reduces both the
frequency of mistakes and the workload for the administrators. This new system
uniquely identifies each reference from its digital object identifier (DOI) and
retrieves the corresponding bibliographic information from any of several
online services, including the SAO/NASA Astrophysics Data Systems (ADS) and
CrossRef APIs. Once parsed into a relational database, the software is able to
produce bibliographies in any of several formats, including HTML and BibTeX,
for use on websites or printed articles. The application is provided
free-of-charge for general use by any scientific database. The power of this
application is demonstrated when used to populate reference data for the HITRAN
and AMBDAS databases as test cases. HITRAN contains data that is provided by
researchers and collaborators throughout the spectroscopic community. These
contributors are accredited for their contributions through the bibliography
produced alongside the data returned by an online search in HITRAN. Prior to
the work presented here, HITRAN and AMBDAS created these bibliographies
manually, which is a tedious, time-consuming and error-prone process. The
complete code for the new referencing system can be found at
\url{https://github.com/hitranonline/refs}.Comment: 11 pages, 5 figures, already published online at
https://doi.org/10.3390/atoms802001
Use of the complete basis set limit for computing highly accurate ab initio dipole moments
Calculating dipole moments with high-order basis sets is generally only
possible for the light molecules, such as water. A simple, yet highly effective
strategy of obtaining high-order dipoles with small, computationally less
expensive basis sets is described. Using the finite field method for computing
dipoles, energies calculated with small basis sets can be extrapolated to
produce dipoles that are comparable to those obtained in high order
calculations. The method reduces computational resources by approximately 50%
(allowing the calculation of reliable dipole moments for larger molecules) and
simultaneously improves the agreement with experimentally measured infrared
transition intensities. For atmospherically important molecules which are
typically too large to consider the use of large basis sets, this procedure
will provide the necessary means of improving calculated spectral intensities
by several percent
Line Strengths of Rovibrational and Rotational Transitions in the X Ground State of OH
A new line list including positions and absolute intensities (in the form of
Einstein values and oscillator strengths) has been produced for the OH
ground X\DP\ state rovibrational (Meinel system) and pure rotational
transitions. All possible transitions are included with v\primed and
v\Dprimed up to 13, and up to between 9.5 and 59.5, depending on the
band. An updated fit to determine molecular constants has been performed, which
includes some new rotational data and a simultaneous fitting of all molecular
constants. The absolute line intensities are based on a new dipole moment
function, which is a combination of two high level ab initio calculations. The
calculations show good agreement with an experimental v=1 lifetime,
experimental values, and v=2 line intensity ratios
from an observed spectrum. To achieve this good agreement, an alteration in the
method of converting matrix elements from Hund's case (b) to (a) was made.
Partitions sums have been calculated using the new energy levels, for the
temperature range 5-6000 K, which extends the previously available (in HITRAN)
70-3000 K range. The resulting absolute intensities have been used to calculate
O abundances in the Sun, Arcturus, and two red giants in the Galactic open and
globular clusters M67 and M71. Literature data based mainly on [O I] lines are
available for the Sun and Arcturus, and excellent agreement is found.Comment: 17 pages, 8 figues. 7 supplementary files: dipole moment functions
(OH-X-DMFs.txt), equilibrium constants (OH-X-Equilibrium_Constants.txt),
partition function (OH-X-Q_5-6000K.dat), PGOPHER file with molecular
constants and transition matric elements (OH-XX.pgo), vibrational Einstein A
and f values (OH-XX-Avv_fvv.txt), line list (OH-XX-Line_list.txt), and
OH-Transformation_Equation_Extra.doc
Origin and extent of the opacity challenge for atmospheric retrievals of WASP-39 b
As the James Webb Space Telescope (JWST) came online last summer, we entered
a new era of astronomy. This new era is supported by data products of
unprecedented information content that require novel reduction and analysis
techniques. Recently, Niraula et al. 2022 (N22) highlighted the need for
upgraded opacity models to prevent facing a model-driven accuracy wall when
interpreting exoplanet transmission spectra. Here, we follow the same approach
as N22 to explore the sensitivity of inferences on the atmospheric properties
of WASP-39 b to the opacity models used. We find that the retrieval of the main
atmospheric properties from this first JWST exoplanet spectrum is mostly
unaffected by the current state of the community's opacity models. Abundances
of strong opacity sources like water and carbon dioxide are reliably
constrained within 0.30 dex, beyond the 0.50 dex accuracy wall reported
in N22. Assuming the completeness and accuracy of line lists, N22's accuracy
wall is primarily driven by model uncertainties on broadening coefficients and
far-wing behaviors, which we find to have marginal consequences for
interpreting the transmission spectra of large, hot, high-metallicity
atmospheres such as WASP-39 b, in opposition to emission spectra and climate
modeling which depend on deeper parts of a planetary atmosphere. The origin of
the opacity challenge in the retrieval of metal-rich hot Jupiters via
transmission spectroscopy will thus mostly stem from the incompleteness and
inaccuracy of line lists.Comment: 10 Pages, 6 Figure
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