J/A+A/605/A95 CH4 and hot methane continuum hybrid line list (Yurchenko+, 2017)
A hybrid line list for CH4 and hot methane continuum.
Yurchenko S.N., Amundsen D.S., Tennyson J., Waldmann I.P.
<Astron. Astrophys. 605, A95 (2017)>
=2017A&A...605A..95Y 2017A&A...605A..95Y (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: molecular data - opacity - infrared: stars -
infrared: planetary systems - line: profiles - methods: numerical
Abstract:
A line list for methane (CH4) is constructed as a combination of 17
million strong absorption lines relative to the reference absorption
spectra and a background methane continuum in two
temperature-dependent forms of cross sections and super-lines. This
approach significantly eases the use of large high temperature line
lists as the computationally expensive calculation of
pressure-dependent profiles (e.g. Voigt) only need to be performed for
a relatively small number of lines. Both the line list and cross
sections were generated using a new 34 billion methane line list
(known as 34to10), which extends the 10to10 line list to higher
temperatures (up to 2000K). The new hybrid scheme can be applied to
any large line lists containing billions of transitions. We recommend
using super-lines generated on a high resolution grid based on a
resolving power of R=1000000 to model the molecular continuum as a
more flexible alternative to the temperature-dependent cross sections.
Description:
The states file ch4_e50.dat contains a list of rovibrational states.
Each state is labelled with: nine normal mode vibrational quantum
numbers and the vibrational symmetry; three rotational quantum numbers
including the total angular momentum J and rotational symmetry; the
total symmetry quantum number Gamma and the running number in the same
(J,Gamma) block. In addition there are nine local mode vibrational
numbers and the largest coefficient used to assign the state in
question. Each rovibrational state has a unique number, which is the
number of the row in which it appears in the file. This number is the
means by which the state is related to the second part of the data
system, the transitions files. The total degeneracy is also given to
facilitate the intensity calculations.
Because of their size, the transitions are listed in 120 separate
files, each containing all the transitions in a 100cm-1 frequency
range. These transition files t_*.dat contain the strong methane lines
lines consisting of three columns: the reference number in the energy
file of the upper state, that of the lower state, the Einstein A
coefficient of the transition and the transition wavenumber. These
entries are ordered by increasing frequency. The name of the file
includes the lowest frequency in the range; thus the t-00500.dat file
contains all the transitions in the frequency range 500-600cm-1.
19 histograms x_YYYYK.dat files contain CH4 super-lines representing
the continuum computed at the temperature T=YYYYK using R=1000000
(7090081 super-lines each) covering the wavenumber range from 10 to
12000cm-1.
The energy file, the transitions files and the histograms files are
bzipped, and need to be extracted before use.
The pressure broadening parameters used in the calculations are listed
in broad.dat.
A programme ExoCross to generate synthetic spectra from these line
lists can be obtained at www.exomol.com.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ch4_e50.dat 163 8194057 Labelled rovibrational states
broad.dat 29 31 Line broadening parameters gamma0 and n0
defining the Voigt profile
trans/* . 120 *Transition files (Einstein coefficients) divided
into 100cm-1 frequency pieces.
hist/* . 20 A set of CH4 super-lines representing methane
continuum at different (T=YYYYK) temperatures
(x_YYYYK.dat)
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Note on trans/* : The transitions are sorted according with wavenumber.
t-xxxxx.dat where xxxxx indicates the lower wavenumber bound.
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See also:
J/ApJ/757/46 : Hot methane (CH4) line list (Hargreaves+, 2012)
J/MNRAS/440/1649 : ExoMol line lists for CH4 (Yurchenko+, 2014)
Byte-by-byte Description of file: ch4_e50.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 I12 --- i State ID, non-negative integer index starting
at 1
14- 25 F12.6 cm-1 E State energy term value in cm-1
27- 32 I6 --- g Total state degeneracy
39- 40 I2 --- J [0/50] J-quantum number J is the total angular
momentum excluding nuclear spin
45 I1 --- G [1/5] Total symmetry in Td(M),
Gamma = A1, A2, E, F1, F2
50- 51 I2 --- n1 [0/10] A1-symmetry normal mode quantum number
(QN)
54- 55 I2 --- n2 [0/20] E-symmetry normal mode QN
58- 59 I2 --- L2 [0/20] L2 vibrational angular momentum QN
62- 63 I2 --- n3 [0/10] F1-symmetry normal mode QN
66- 67 I2 --- L3 [0/10] L3 vibrational angular momentum QN
70- 71 I2 --- M3 [0/10] M3 Multiplicity index QN
74- 75 I2 --- n4 [0/20] F2-symmetry normal mode QN
78- 79 I2 --- L4 [0/20] L4 vibrational angular momentum QN
82- 83 I2 --- M4 [0/20] M4 Multiplicity index QN
88 I1 --- Gv [1/5] Td(M) vibrational symmetry {GAMMA}(v)
(local mode)
94- 95 I2 --- J2 [0/50] Total angular momentum quantum number
Same column as J
98- 99 I2 --- K [0/50] Projection of J on axis of molecular
symmetry
103 I1 --- Pr [0/1] Rotational parity tau(rot)
107 I1 --- Grot [1/5] Td(M) rotational symmetry {GAMMA}(rot)
111-117 I7 --- NBl [1/9997054] Reference number in the block
121-124 F4.2 --- C2 [0.0/1.00] Square of the largest coefficient
130-131 I2 --- v1 [0/10] Local mode vibrational quantum number
134-135 I2 --- v2 [0/10] Local mode vibrational QN
138-139 I2 --- v3 [0/10] Local mode vibrational QN
142-143 I2 --- v4 [0/10] Local mode vibrational QN
146-147 I2 --- v5 [0/20] Local mode vibrational QN
150-151 I2 --- v6 [0/20] Local mode vibrational QN
154-155 I2 --- v7 [0/20] Local mode vibrational QN
158-159 I2 --- v8 [0/20] Local mode vibrational QN
162-163 I2 --- v9 [0/20] Local mode vibrational QN
-------------------------------------------------------------------------------
Byte-by-byte Description of file: broad.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Type a0-type, see definition in Tennyson, 2016,
J. Mol. Spectrosc., 327, 73
4- 10 F7.3 cm-1 gamma0 Voigt gamma parameter (CH4)
12- 20 F9.3 --- n Temperature exponent (CH4)
22- 29 I8 --- J" Lower state rotational quantum number J"
-------------------------------------------------------------------------------
Byte-by-byte Description of file: trans/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 I12 --- i" Upper state ID
14- 25 I12 --- i' Lower state ID
27- 36 E10.4 s-1 A Einstein A-coefficient of the transition
-------------------------------------------------------------------------------
Byte-by-byte Description of file: hist/*
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Bytes Format Units Label Explanations
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1- 17 E17.8 cm-1 nu Frequency wavenumber
19- 34 E16.8 cm/mol I(T) Absorption coefficient at T=YYYYK (in cm/molecule)
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Acknowledgements:
S.N. Yurchenko, s.yurchenko(at)ucl.ac.uk
J. Tennyson, j.tennyson(at)ucl.ac.uk
(End) Patricia Vannier [CDS] 10-Jul-2017