J/ApJS/240/4 High-temperature methane cross-sections (Wong+, 2019)
Atlas of experimental and theoretical high-temperature methane cross-sections
from T=296 K to 1000 K in the near infrared.
Wong A., Bernath P.F., Rey M., Nikitin A.V., Tyuterev V.G.
<Astrophys. J. Suppl. Ser. 240, 4 (2019)>
=2019ApJS..240....4W 2019ApJS..240....4W (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: astronomical databases: miscellaneous - infrared: general -
molecular data
Abstract:
Spectra of hot methane were recorded using a tube furnace and a
high-resolution Fourier transform spectrometer. We obtained
experimental absorption spectra in the 1.85-1.11um near-infrared
region at eight temperatures ranging from 295K up to 1000K. We have
converted these into an atlas of absorption cross sections at each
temperature for the methane tetradecad, icosad and triacontad polyads,
excluding some spectral intervals either strongly contaminated by
water or due to baseline fringes. On the theoretical side, the spectra
were simulated from the ab initio-based Reims-Tomsk TheoReTS line list
for the same experimental conditions. This line list has been
constructed by global variational calculations from potential energy
and dipole moment surfaces followed by empirical line position
corrections deduced from previously published analyses. The
comparisons showed very good overall agreement between observations
and theory at high spectral resolution for the tetradecad and icosad
and at medium or low resolution above this range. A full set of the
theoretical absorption cross sections is also included. Detailed
temperature dependence of the methane absorption enables the efficient
method of remotely probing the temperature of distant astronomical
objects based on a comparison of relative signals in carefully
selected spectral intervals. This first combined experimental and
theoretical easy-to-use cross-section library in the near-infrared
should be of major interest for the interpretation of current and
future astronomical observations up to a resolving power of
100000-300000 in the range 6400-7600cm-1 and a resolving
power of 5000-10000 in the higher wavenumber range up to 9000cm-1.
Description:
Spectra of hot methane (up to 1000K) were recorded at Old Dominion
University using a tube furnace, a quartz cell (optical path length of
50cm), and a Bruker IFS 120/125HR (120 bench upgraded with 125
electronics) Fourier transform spectrometer. The spectrometer was
equipped with a CaF2 beamsplitter, a liquid N2-cooled InSb detector,
an optical filter, and an external halogen lamp to produce radiation
covering a spectral range between 5200 and 9200cm-1 (1.92-1.08um)
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tables1.dat 39 4047349 Experimental high-temperature methane cross-sections
tables2.dat 39 25919962 Theoretical high-temperature methane cross-sections
--------------------------------------------------------------------------------
See also:
J/ApJ/813/12 : Empirical methane (CH4) line list (Hargreaves+, 2015)
Byte-by-byte Description of file: tables1.dat tables2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.3 cm-1 Res Resolution (0.02, 0.2, 2)
7- 12 F6.1 K T Temperature
(295, 400, 500, 600, 700, 800, 900, 1000)
14- 24 F11.6 cm-1 lambda Wavelength
26- 39 E14.9 cm+2 CS Cross-section (cm2/molecule)
--------------------------------------------------------------------------------
Acknowledgements:
Michael Rey, michael.rey(at)univ-reims.fr
(End) Patricia Vannier [CDS] 06-Aug-2018