J/A+A/658/A127 Spectroscopy of CD3OH (Ilyushin+, 2022)
Rotational and rovibrational spectroscopy of CD3OH and an account on CD3OH
toward IRAS 16293-2422.
Ilyushin V.V., Muller H.S.P., Jorgensen J.K., Bauerecker S., Maul C.,
Bakhmat Y., Alekseev E.A., Dorovskaya O., Vlasenko S., Lewen F.,
Schlemmer S., Berezkin K., Lees R.M.
<Astron. Astrophys. 658, A127 (2022)>
=2022A&A...658A.127I 2022A&A...658A.127I (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium; Spectra, millimetric/submm; Spectroscopy
Keywords: molecular data - methods: laboratory: molecular -
techniques: spectroscopic - radio lines: ISM - ISM: molecules -
astrochemistry
Abstract:
Solar-type protostars have been shown to harbor highly deuterated
complex organics as for example witnessed by the high relative
abundances of doubly and triply deuterated isotopologs. While this
degree of deuteration may provide important clues to the formation of
these species, spectroscopic information on multiply deuterated
isotopologs is often insufficient. In particular, searches for triply
deuterated methanol, CD3OH, are hampered to a large extent by the
lack of intensity information from a spectroscopic model. The aim of
the present study is to develop a spectroscopic model of CD3OH in
low-lying torsional states sufficiently accurate to facilitate further
searches for CD3OH in space. We have performed a new measurement
campaign for CD3OH involving three spectroscopic laboratories which
covers the 34GHz-1.1THz and the 20-900cm-1 ranges. The analysis was
perfomed using the rho-axis-method torsion- rotation Hamiltonian
model. We determined a model that describes the ground and first
excited torsional states of CD3OH up to quantum numbers J≤55 and
K≤23, and derived a line list for radio-astronomical observations.
The resulting line list is accurate up to at least 1.1THz and should
be sufficient for all types of radio-astronomical searches for this
methanol isotopolog. This line list was used to search for CD3OH in
data from the Protostellar Interferometric Line Survey of IRAS
16293-2422 using the Atacama Large Millimeter/submillimeter Array.
CD3OH is securely detected in the data with a large number of
clearly separated and well-reproduced lines. We detected not only
lines belonging to the ground torsional state, but also several
belonging to the first excited torsional state. The derived column
density of CD3OH and abundance relative to non-deuterated isotopolog
confirm the significant enhancement of this multiply deuterated
variant. This is in line with other observations of multiply
deuterated complex organic molecules and may serve as an important
constraint on models for their formation.
Description:
Table A1 contains assigned microwave transitions of the CD3OH spectrum
used in the analysis. Source of data: Khark - Kharkov spectrometer,
present work; Koln - Cologne spectrometers, present work; for other
source codes (B,C,D,F) see Walsh M.S., Xu L.-H., & Lees R.M. 1998, J.
Mol. Spectrosc., 188, 85.
Table A2 contains assigned FIR transitions of the CD3OH spectrum used
in the analysis. Source of data: Braunschweig measurements, present
work.
Table A3 contains predicted transitions of the ground and first
excited torsional states of CD3OH in the frequency range from 1GHz up
to 1.3THz with J up to 60 and |Ka| up to 24. The m values 0/1 and
-3/-2 correspond to A/E transitions of the vt=0 and 1 torsional
states, respectively. We limit our calculations to transitions for
which uncertainties are less than 0.1 MHz.
Table A4 contains torsion-rotation part Qrt(T) of the total internal
partition function Q(T)=Qv(T)*Qrt(T), calculated for CD3OH from first
principles using the parameter set of Table 2. The vibrational part
Qv(T) (omitting the torsional vibration since it is taken into account
in Qrt) may be estimated in the harmonic approximation using the
vibrational frequencies reported by T. Schimanouchi, Tables of
Molecular Vibrational Frequencies, Vol. I: consolidated (National
Bureau of Standards, Washington, DC, 1972), pp. 1-160. In the
calculation the states up to J=100 and vt=11 were included.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 75 8580 Assigned microwave transitions of the CD3OH
spectrum used in the analysis
tablea2.dat 71 7218 Assigned FIR transitions of the CD3OH spectrum
used in the analysis
tablea3.dat 87 24574 Predicted transition frequencies of the ground
and first excited torsional states of CD3OH
in the frequency range from 1GHz up to 1.3THz
tablea4.dat 16 30 Torsion-rotation part Qrt(T) of the total
internal partition function Q(T)=Qv(T)*Qrt(T),
calculated for CD3OH from first principles
(corrected version, 20-Mar-2022)
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Sym' Upper level symmetry in the G6 group
4- 5 I2 --- m' Upper free rotor torsional quantum number
7- 9 I3 --- J' Upper J quantum number
11- 13 I3 --- Ka' Upper Ka quantum number
15- 17 I3 --- Kc' Upper Kc quantum number
22- 23 A2 --- Sym" Lower level symmetry in the G6 group
25- 26 I2 --- m" Lower free rotor torsional quantum number
28- 30 I3 --- J" Lower J quantum number
32- 34 I3 --- Ka" Lower Ka quantum number
36- 38 I3 --- Kc" Lower Kc quantum number
40- 51 F12.3 MHz Freq Observed transition frequency
54- 59 F6.3 MHz unc Uncertainty of measurement
62- 69 F8.4 MHz O-C Residuals from the fit
72- 75 A4 --- Cmnt Source of data
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- Sym' Upper level symmetry in the G6 group
4- 5 I2 --- m' Upper free rotor torsional quantum number
7- 9 I3 --- J' Upper J quantum number
11- 13 I3 --- Ka' Upper Ka quantum number
15- 17 I3 --- Kc' Upper Kc quantum number
22- 23 A2 --- Sym" Lower level symmetry in the G6 group
25- 26 I2 --- m" Lower free rotor torsional quantum number
28- 30 I3 --- J" Lower J quantum number
32- 34 I3 --- Ka" Lower Ka quantum number
36- 38 I3 --- Kc" Lower Kc quantum number
40- 49 F10.4 cm-1 Freq Observed transition frequency
53- 59 F7.4 cm-1 unc Uncertainty of measurement
63- 71 F9.5 cm-1 O-C Residuals from the fit
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Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- Sym' Upper level symmetry in the G6 group
4- 5 I2 --- m' Upper free rotor torsional quantum number
7- 9 I3 --- J' Upper J quantum number
11- 13 I3 --- Ka' Upper Ka quantum number
15- 17 I3 --- Kc' Upper Kc quantum number
22- 23 A2 --- Sym" Lower level symmetry in the G6 group
25- 26 I2 --- m" Lower free rotor torsional quantum number
28- 30 I3 --- J" Lower J quantum number
32- 34 I3 --- Ka" Lower Ka quantum number
36- 38 I3 --- Kc" Lower Kc quantum number
40- 52 F13.4 MHz Freq Predicted transition frequency
55- 62 F8.4 MHz unc Predicted uncertainty of transition frequency
66- 75 F10.4 cm-1 Elo The energy of the lower state
78- 87 E10.3 D+2 Sm2 Dipole moment squared multiplied by the
transition linestrength and nuclear spin
statistical weight
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.1 K T Temperature
8- 16 F9.2 --- Qrt Torsion-rotation part of the partition function
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Acknowledgements:
Vadim Ilyushin, ilyushin(at)rian.kharkov.ua
History:
10-Feb-2022: on-line version
20-Mar-2022: tablea4 corrected (from author)
(End) Vadim Ilyushin [IRA NASU], Patricia Vannier [CDS] 08-Nov-2021