J/A+A/677/A49 Spectroscopy of CD3OD (Ilyushin+, 2023)
Investigation of the rotational spectrum of CD3OD and an astronomical
search for it toward IRAS 16293-2422.
Ilyushin V.V., Muller H.S.P., Jorgensen J.K., Bauerecker S., Maul C.,
Porohovoi R., Alekseev E.A., Dorovskaya O., Lewen F., Schlemmer S.,
Lees R.M.
<Astron. Astrophys. 677, A49 (2023)>
=2023A&A...677A..49I 2023A&A...677A..49I (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 prestellar cores and protostars display frequently large
amounts of deuterated organic molecules and in particular high
relative abundances of doubly and triply deuterated isotopologs.
Recent findings on CHD2OH and CD3OH toward IRAS 16293-2422 suggest
that even fully deuterated methanol, CD3OD, may be detectable as
well. However, searches for CD3OD are hampered in particular by the
lack of intensity information from a spectroscopic model. The
objective of the present investigation is to develop a spectroscopic
model of CD3OD in low-lying torsional states that is sufficiently
accurate to facilitate searches for this isotopolog in space. We
carried out a new measurement campaign for CD3OD involving two
spectroscopic laboratories that covers the 34 GHz-1.1THz range. A
torsion-rotation Hamiltonian model based on the rho-axis method was
employed for our analysis. Our resulting model describes the ground
and first excited torsional states of CD3OD well up to quantum
numbers J≤51 and Ka≤23. We derived a line list for
radio-astronomical observations from this model that 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 CD3OD in data from the Protostellar
Interferometric Line Survey of IRAS 16293-2422 obtained with the
Atacama Large Millimeter/ submillimeter Array. While we found several
emission features that can be attributed largely to CD3OD, their
number is as yet insufficient to establish a clear detection.
Nevertheless, the estimate of 2x1015cm-2^ derived for the CD3OD
column density may be viewed as an upper limit that can be compared to
column densities of CD3OH, CH3OD, and CH3OH. The comparison
indicates that the CD3OD column density toward IRAS 16293-2422 is in
line with the enhanced D/H ratios observed for multiply deuterated
complex organic molecules.
Description:
Table B1 contains assigned microwave transitions of the CD3OD
spectrum used in the analysis. Source of data: Khark - Kharkov
spectrometer, present work; Koln - Cologne spectrometers, present
work; for other source codes (A,C,D,E,F) see H.S.P. Muller, L.-H. Xu,
& F. van der Tak 2006, J. Mol. Struct., 795, 114.
Table B2 contains assigned FIR transitions of the CD3OD spectrum
used in the analysis. Source of data: I. Mukhopadhyay, Infrared
Physics & Technology 114 (2021) 103668.
Table B3 contains predicted transitions of the ground and first
excited torsional states of CD3OD in the frequency range from 1GHz
up to 1.33THz with J up to 55 and |Ka| up to 25. 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 B4 contains torsion-rotation part Qrt(T) of the total internal
partition function Q(T)=Qv(T)*Qrt(T), calculated for CD3OD from first
principles using the parameter set of Table A.1. 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=90 and vt=11 were included.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 76 11232 Assigned microwave transitions of the CD3OD
spectrum used in the analysis
tableb2.dat 71 5027 Assigned FIR transitions of the CD3OD
spectrum used in the analysis
tableb3.dat 87 32334 Predicted transition frequencies of the ground
and first excited torsional states of CD3OD
in the frequency range from 1GHz up to 1.33THz
tableb4.dat 16 30 Torsion-rotation part Qrt(T) of the total
internal partition function Q(T)=Qv(T)*Qrt(T),
calculated for CD3OD from first principles
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Byte-by-byte Description of file: tableb1.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- 76 A5 --- Cmnt Source of data (1)
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Note (1): Source of data as follows:
Khark = Kharkov spectrometer, present work
Koln = Cologne spectrometers, present work
A = see Muller, Xu, & van der Tak 2006, J. Mol. Struct., 795, 114
C = see Muller, Xu, & van der Tak 2006, J. Mol. Struct., 795, 114
D = see Muller, Xu, & van der Tak 2006, J. Mol. Struct., 795, 114
E = see Muller, Xu, & van der Tak 2006, J. Mol. Struct., 795, 114
F = see Muller, Xu, & van der Tak 2006, J. Mol. Struct., 795, 114
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Byte-by-byte Description of file: tableb2.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- 50 F11.5 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: tableb3.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 D2 Sm2 Dipole moment squared multiplied by the
transition linestrength and nuclear spin
statistical weight
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Byte-by-byte Description of file: tableb4.dat
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Bytes Format Units Label Explanations
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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
(End) Vadim Ilyushin [IRA NASU], Patricia Vannier [CDS] 02-Jul-2023