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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 (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:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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
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.
Byte-by-byte Description of file: fig2.dat
Bytes Format Units Label Explanations
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
History: From electronic version of the journal
(End) Prepared by [AAS], Patricia Vannier [CDS] 01-Mar-2017
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