J/ApJ/789/2 Methane partition function (Rey+, 2014)
Theoretical hot methane line lists up to T = 2000 K for astrophysical
applications.
Rey M., Nikitin A.V., Tyuterev V.G.
<Astrophys. J., 789, 2 (2014)>
=2014ApJ...789....2R 2014ApJ...789....2R (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Line Profiles ; Spectra, infrared
Keywords: brown dwarfs - infrared: general - methods: numerical - molecular data
Abstract:
The paper describes the construction of complete sets of hot methane
lines based on accurate ab initio potential and dipole moment surfaces
and extensive first-principle calculations. Four line lists spanning
the [0-5000]/cm infrared region were built at T = 500, 1000, 1500, and
2000 K. For each of these four temperatures, we have constructed two
versions of line lists: a version for high-resolution applications
containing strong and medium lines and a full version appropriate for
low-resolution opacity calculations. A comparison with available
empirical databases is discussed in detail for both cold and hot bands
giving a very good agreement for line positions, typically <0.1-0.5/cm
and ∼5% for intensities of strong lines. Together with numerical tests
using various basis sets, this confirms the computational convergence
of our results for the most important lines, which is the major issue
for theoretical spectra predictions. We showed that transitions with
lower state energies up to 14,000/cm could give significant
contributions to the methane opacity and have to be systematically
taken into account. Our list at 2000 K calculated up to J = 50
contains 11.5 billion transitions for I > 10-29 cm/mol. These new
lists are expected to be quantitatively accurate with respect to the
precision of available and currently planned observations of
astrophysical objects with improved spectral resolution.
Description:
In this work, we extend our theoretical predictions for methane
absorption/emission lines to high temperatures (T ∼ 2000 K) that are
relevant for astrophysical applications. The aim is a construction of
complete line lists accounting for all HB transitions which could
contribute to the absorption or emission at these extreme conditions
with a subsequent validation against available high-resolution
experimental spectra.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 49 156 Methane partition function calculated from
variational rovibrational energy levels
fig2.dat 30 50 Number of lines and convergence of the
integrated intensity as a function of the
intensity cutoff for different temperatures
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See also:
J/ApJ/757/46 : Hot methane (CH4) line list (Hargreaves+, 2012)
J/ApJ/813/12 : Empirical methane (CH4) line list (Hargreaves+, 2015)
J/MNRAS/440/1649 : ExoMol line lists for CH4 (Yurchenko+, 2014)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 F6.1 K Temp Temperature
8- 17 F10.3 --- Q Partition function from his work
19 A1 --- f_Q Flag on Q (1)
21- 29 F9.2 --- HITRAN ? HITRAn partition function
31- 33 F3.1 % e_HITRAN ? Percentage error between HITRAN and this work
35- 43 F9.2 --- Wenger ? Wenger et al. (2008, JQSRT, 109, 2687)
partition function
45- 49 F5.2 % e_Wenger ? Percentage error between Wenger and this work
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Note (1): Flag as follows:
a = 54175.0 extrapolated at J infinity;
b = 72602.0 extrapolated at J infinity;
c = 96400.0 extrapolated at J infinity;
d = 126735.0 extrapolated at J infinity;
e = 165270.0 extrapolated at J infinity.
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Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 K Temp Temperature
6- 7 I2 --- ICut Intensity cutoff; 10-ncm/mol
9- 19 I11 --- Num Number of lines
21- 30 E10.4 cm/mol Sum Integrated intensity
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History:
From electronic version of the journal
(End) Prepared by [AAS], Patricia Vannier [CDS] 01-Mar-2017