J/ApJ/782/75 Complete spectrum of methanol (Fortman+, 2014)
The complete, temperature resolved experimental spectrum of methanol (CH3OH)
between 560 and 654 GHz.
Fortman S.M., Neese C.F., De Lucia F.C.
<Astrophys. J., 782, 75 (2014)>
=2014ApJ...782...75F 2014ApJ...782...75F (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Spectroscopy ; Interstellar medium
Keywords: astrochemistry - astronomical databases: miscellaneous -
ISM: molecules - methods: laboratory: molecular - molecular data
Abstract:
The complete spectrum of methanol (CH3OH) has been characterized
over a range of astrophysically significant temperatures in the
560.4-654.0GHz spectral region. Absolute intensity calibration and
analysis of 166 experimental spectra recorded over a slow 248-398K
temperature ramp provide a means for the simulation of the complete
spectrum of methanol as a function of temperature. These results
include contributions from vt=3 and other higher states that are
difficult to model via quantum mechanical (QM) techniques. They also
contain contributions from the 13C isotopologue in terrestrial
abundance. In contrast to our earlier work on semi-rigid species, such
as ethyl cyanide and vinyl cyanide, significant intensity differences
between these experimental values and those calculated by QM methods
were found for many of the lines. Analysis of these differences shows
the difficulty of the calculation of dipole matrix elements in the
context of the internal rotation of the methanol molecule. These
results are used to both provide catalogs in the usual line frequency,
linestrength, and lower state energy format, as well as in a frequency
point-by-point catalog that is particularly well suited for the
characterization of blended lines.
Description:
The 166 values of the spectroscopic temperature (T) and the nL/Q
factor are shown in Table1.
Table2 shows the 1.9 million pairs of Sijµ2 and E that
characterize the spectrum of methanol as a function of temperature.
The first of the pairs in the electronic archive is at 560GHz and
subsequent points are incremented by 0.048828125MHz.
For ease of use, the point-by-point analysis was used to construct a
more compact file in the standard astrophysical catalog format. The
results for the 991 lines are shown in Table3. This table was
constructed by using a peak finder to locate the spectral lines and
then using the values of Sijµ2 and E at line center from Table2
for the Sijµ2 and E shown in Table3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 21 166 *Temperatures T and nL/Q parameters derived from
fits to reference lines from the Quantum
Mechanical (QM) catalogs
table2.dat 25 1916928 1.9 million pairs that characterize the methanol
spectrum as a function of temperature
table3.dat 29 991 Line list catalog in the standard astrophysical
catalog format
spectra/* . 166 Absorption cross section
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Note on table1.dat: Full table downloaded on
https://osu.box.com/s/w614gxfosob1a8cctfawv3imd2s0s43q - 2016-12-19
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See also:
J/ApJ/714/476 : Complete spectrum of ethyl cyanide (Fortman+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I03 --- Index [0/165] Index of the temperature scan
5- 11 F7.3 K T [248/398] Spectroscopic temperature
13- 21 F9.7 nm-2 nL/Q [0.0489/0.25] The nL/Q factor (1)
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Note (1): Here n is the number density, L the effective path length, and Q the
partition function.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 15 F15.3 D2 Sijmu2 [0/7.7250e+10] The Sijµ2 coefficient (G1)
17- 25 F9.3 cm-1 E [-8/10010] E coefficient (transition energy) (G1)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 F10.3 MHz Freq [561025/653185] Frequency
12- 20 F9.3 D2 Sijmu2 [0.017/14765] Line strength Sijµ2 (G1)
22- 29 F8.3 cm-1 E [0/2417] Lower state energy (G1)
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Byte-by-byte Description of file: spectra/*
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Bytes Format Units Label Explanations
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1- 14 E14.11 nm2 ACS [-1/4] Absorption cross section (1)
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Note (1): Files named SpecNNNT=TTT.TTK.txt where NNN is the index of the
temperature scan as in Table1, and TTT.TT is the associated spectroscopic
temperature. Absorption cross section values are function of the frequency
starting at 560GHz (560000.0MHz) and incrementing in steps of
0.048828125MHz, covering therefore the frequency range 560-654GHz.
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Global Notes:
Note (G1): The coefficients are defined in Eqs. (3) and (4). Table2 contains 1.9
million pairs of Sijµ2 and E coefficients, as a function of the
frequency starting at 560GHz (560000.0MHz) and incrementing in steps of
0.048828125MHz, covering therefore the frequency range 560-654GHz.
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History:
* 10-Mar-2016: From electronic version of the journal, ten rows only in
Table1
* 19-Aug-2016: Complete Table1 (166 values of T and nL/Q) from authors
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 10-Mar-2016