J/A+A/659/A69 Di-deuterated methanol (CHD2OH) line list (Drozdovskaya+, 2022)
Successive deuteration in low-mass star-forming regions:
the case of D2-methanol (CHD2OH) in IRAS 16293-2422.
Drozdovskaya M.N., Coudert L.H., Margules L., Coutens A., Jorgensen J.K.,
Manigand S.
<Astron. Astrophys. 659, A69 (2022)>
=2022A&A...659A..69D 2022A&A...659A..69D (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: astrochemistry - ISM: molecules - stars: protostars -
stars: formation - ISM: individual objects: IRAS 16293-2422 -
submillimeter: ISM
Abstract:
Di-deuterated molecules are observed in the earliest stages of star
formation at abundances of a few percent relative to their
nondeuterated isotopologs, which is unexpected considering the
scarcity of deuterium in the interstellar medium. With sensitive
observations leading to the detection of a steadily increasing number
of di-deuterated species, it is becoming possible to explore
successive deuteration chains.
The accurate quantification of the column density of di-deuterated
methanol is a key piece of the puzzle that is missing in the otherwise
thoroughly constrained family of D-bearing methanol in the deeply
embedded low-mass protostellar system and astrochemical template
source IRAS 16293-2422. A spectroscopic dataset for astrophysical
purposes was built for CHD2OH and made publicly available to
facilitate the accurate characterization of this species in
astrochemical surveys.
The newly computed line list and partition function were used to
search for CHD2OH toward IRAS 16293-2422 A and B in data from the
Atacama Large Millimeter/submillimeter Array (ALMA) Protostellar
Interferometric Line Survey (PILS). Only nonblended, optically thin
lines of CHD2OH were used for the synthetic spectral fitting.
The constructed spectroscopic database contains line frequencies and
strengths for 7417 transitions in the 0-500GHz frequency range.
ALMA-PILS observations in the 329-363GHz range were used to identify
105 unique, nonblended, optically thin line frequencies of CHD2OH for
synthetic spectral fitting. The derived excitation temperatures and
column densities yield high D/H ratios of CHD2OH in IRAS 16293-2422 A
and B of 7.5±1.1% and 7.7±1.2%, respectively.
Deuteration in IRAS 16293-2422 is not higher than in other low-mass
star-forming regions (L483, SVS13-A, NGC 1333-IRAS2A, -IRAS4A, and
-IRAS4B). Di-deuterated molecules consistently have higher D/H ratios
than their mono-deuterated counterparts in all low-mass protostars,
which may be a natural consequence of H-D substitution reactions as
seen in laboratory experiments. The Solar System's natal cloud, as
traced by comet 67P/Churyumov-Gerasimenko, may have had a lower
initial abundance of D, been warmer than the cloud of IRAS 16293-2422,
or been partially reprocessed. In combination with accurate
spectroscopy, a careful spectral analysis, and the consideration of
the underlying assumptions, successive deuteration is a robust window
on the physicochemical provenance of star-forming systems.
Description:
The constructed spectroscopic database for di-deuterated methanol
(CHD2OH) containing line frequencies and strengths for 7417
transitions in the 0 to 500GHz frequency range. It is formatted in
the same way as the catalog line files of the JPL database (Pickett et
al., 1998, J. Quant. Spectr. Rad. Transf., 60, 883) and displays 16
columns.
Species Tag: 34002 Name: CD2HOH
Version: 1 Doubly-deuterated methanol
Date: September 2021 v = 0, 1 and 2 (e0, o1, e1)
Contributor: L. H. Coudert A' & A" species
Lines Listed: 7417 Q(300.0) = 19423.4376
Freq. (GHz) < 500 Q(225.0) = 11268.4157
Max. J 26 Q(150.0) = 5255.8661
LOGSTR0 = -9 Q(75.00) = 1563.4091
LOGSTR1 = -9 Q(37.50) = 490.4886
Egy. (cm-1) > 0 Q(18.75) = 145.2964
µa = 0.8956 Q(9.375) = 39.8511
µb = 1.37 Q(5.000) = 12.4120
µc = 0 Q(2.725) = 4.5666
The linelist is based on an analysis of microwave, sub-millimeter
wave, terahertz, and FIR data pertaining to CD2 HOH [Coudert,
Motiyenko, Margules, Kwabia Tchana, J. Mol. Specrosc. (2021)
accepted]. Energy levels were calculated using the theoretical
approach developed for CH2 DOH [Coudert, Zemouli, Motiyenko,
Margules, & Klee, J. Chem. Phys. 140 2014) 064307]. The fitted data
involve torsion-rotation transitions with 0≤v≤2, up to J=26.
Torsional levels v = 0, 1, and 2 can be respectively labeled
e0, o1, and e1 with the abeling scheme of Su and Quade
[Su & Quade, J. Mol. Spectrosc. 134 (1989) 290].
The linelist is formatted as a JPL catalogue line file [Pickett,
Poynter, Cohen, Delitsky, Pearson, & Muller, J. Quant. Spectrosc.
Radiat. Transfer, 60 (1998), pp. 883-890]. Transitions are assigned
with the rotational quantum numbers J, K, p, with 0≤K≤J and p=1 or
2, defined in accordance with Coudert et al., and the torsional
quantum number v.
The dipole moment components are given in Debye in the molecule fixed
axis system of Coudert et al. such that the axis of internal rotation
is parallel to the molecule fixes z-axis. The partition function Q(T)
was determined taking a zero energy for the v=0, A',J=K=0, p=1 lowest
lying level; a degeneracy factor of (2J+1); and a maximum J-value of
40.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
c034006.dat 75 7417 Full line list
d034006.pdf 512 165 Information
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Byte-by-byte Description of file: c034006.dat
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Bytes Format Units Label Explanations
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1- 13 F13.4 MHz Freq Line frequency (FREQ) (1)
14- 21 F8.4 MHz e_Freq Error in line frequency (ERR) (1)
22- 29 F8.4 nm+2.MHz logInt base-10 logarithm of the line intensity
(in nm2xMHz units) at 300K (LGINT)
30- 31 I2 --- DR Degrees of freedom of rotational partition
function (DR)
32- 41 F10.4 cm-1 Elo Lower state energy (ELO)
42- 44 I3 --- Gup Upper state degeneracy (GUP)
45- 52 I8 --- Tag Species tag (TAG)
53- 55 I3 --- QNFMT Format number (QNFMT)
56- 63 A8 --- UJKp Assigned upper rotational quantum numbers
J,K,p (UJKp) (2)
68- 75 A8 --- LJKp Assigned lower rotational quantum numbers
J,K,p (LJKp) (2)
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Note (1): For observed non-blended microwave lines, the line frequency (FREQ)
and the error (ERR) were replaced by their experimental values. This is
then indicated by a negative species tag.
A minimum value of 10kHz was selected for the calculated error (ERR).
Note (2): upper and lower level in terms of the
rotational quantum numbers J, K, p introduced by Coudert et al. (2021,
Journal of Molecular Spectroscopy, 381, 111515) and the torsional
quantum number vt.
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Acknowledgements:
Maria Drozdovskaya, maria.drozdovskaya(at)unibe.ch
(End) Patricia Vannier [CDS] 19-Jan-2022