J/ApJ/795/56 Experimental spectrum of methanol (CH3OH) (McMillan+, 2014)
The complete, temperature resolved experimental spectrum of methanol (CH3OH)
between 214.6 and 265.4 GHz.
McMillan J.P., Fortman S.M., Neese C.F., De Lucia F.C.
<Astrophys. J., 795, 56 (2014)>
=2014ApJ...795...56M 2014ApJ...795...56M (SIMBAD/NED BibCode)
ADC_Keywords: Spectroscopy ; Atomic physics
Keywords: astrochemistry - molecular data
Abstract:
The spectrum of methanol (CH3OH) has been characterized between
214.6 and 265.4 GHz for astrophysically significant temperatures. Four
hundred and eighty-six spectra with absolute intensity calibration
recorded between 240 and 389 K provided a means for the calculation of
the complete experimental spectrum (CES) of methanol as a function of
temperature. The CES includes contributions from vt=3 and other
higher states that are difficult to model quantum mechanically (QM).
It also includes the spectrum of the 13C isotopologue in terrestrial
abundance. In general the QM models provide frequencies that are
within 1 MHz of their experimental values, but there are several
outliers that differ by tens of MHz. As in our recent work on methanol
in the 560-654 GHz region, significant intensity differences between
our experimental intensities and cataloged values were found. In this
work these differences are explored in the context of several QM
analyses. The experimental results presented here are analyzed to
provide a frequency point-by-point catalog that is well suited for the
simulation of crowded and overlapped spectra. Additionally, a catalog
in the usual line frequency, line strength, and lower state energy
format is provided.
Description:
In this paper we describe the spectrum of methanol between 214.6 and
265.4 GHz. In this region we observed 589 lines with scaled
absorbance cross-sections greater than 0.0037 nm2. For comparison
there are 386 lines in a composite catalog above this scaled
absorbance cross-section. The spectrometer uses ax24 frequency
multiplied probe, a heterodyne receiver, and a temperature controlled
6 m long cell (Fortman et al. 2010ApJ...725.1682F 2010ApJ...725.1682F, 2011ApJ...737...20F 2011ApJ...737...20F).
Four hundred eighty-six spectral scans were recorded as the
temperature was ramped over a period of 305 minutes from 240 K to
389 K. The spectrum was recorded at 24.4140625 kHz intervals, with
an integration time of ∼18 us/bin.
The temperatures were determined spectroscopically and are used as a
part of the file name. The decontaminated absorbance spectra data are
contained in 486 flat text files in this tarball. Each spectrum file
contains 2.08 million data bins, starting at 214.6 GHz and
incrementing in steps of 24.4140625 kHz. The frequency (in MHz) is
provided in "tablefre.dat" and calibration data are provided in
"tablecal.dat"
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 100 592 Line catalog
tablecal.dat 20 486 Calibration Data
tablefre.dat 17 2080000 Frequency in MHz for all scans
sp/* . 485 Individual spectra for frequencies listed in
tablefre.dat
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See also:
J/ApJ/782/75 : Complete spectrum of methanol (Fortman+, 2014)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Snippet [0/556] Snippet Index
7- 10 A4 --- Ref Reference Index
12- 20 F9.5 D2 S Line Strength
22- 30 F9.5 D2 e_S Line Strength Uncertainty
32- 40 F9.3 cm-1 E Lower State Energy
42- 50 F9.3 cm-1 e_E Lower State Energy Uncertainty
52- 65 F14.6 MHz nu Frequency
67- 75 F9.6 MHz e_nu Frequency Uncertainty
77- 85 F9.6 MHz LW Lorentzian HWHM @ 300 K
87- 95 F9.6 MHz e_LW Lorentzian HWHM Uncertainty
97-100 I4 --- C13 Line attributed to Carbon-13
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Byte-by-byte Description of file: tablecal.dat
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Bytes Format Units Label Explanations
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1- 3 I03 --- Index [0/485] Index of the Scan
6- 11 F6.2 K T Spectroscopic Temperature
12- 20 F9.5 nm-2 N Effective Column Density
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Byte-by-byte Description of file: tablefre.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 17 F17.10 MHz Freq Frequency
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 8 A8 --- Abs Napierian Absorbance spectra
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 18-May-2017