J/A+A/659/A111 The rotational spectrum of acrylamide (Kolesnikova+, 2022)
Laboratory rotational spectroscopy of acrylamide and a search for acrylamide
and propionamide toward Sgr B2(N) with ALMA.
Kolesnikova L., Belloche A., Koucky J., Alonso E.R., Garrod R.T.,
Lukova K., Menten K.M., Muller H.S.P., Kania P., Urban S.
<Astron. Astrophys. 659, A111 (2022)>
=2022A&A...659A.111K 2022A&A...659A.111K (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics; Interstellar medium; Spectroscopy
Keywords: astrochemistry - ISM: molecules - line: identification -
ISM: individual objects: Sagittarius B2 -
astronomical databases: miscellaneous
Abstract:
Numerous complex organic molecules have been detected in the universe
and among them are amides, which are considered as prime models for
species containing a peptide linkage. In its backbone, acrylamide
(CH2CHC(O)NH2) bears not only the peptide bond, but also the vinyl
functional group that is a common structural feature in many
interstellar compounds. This makes acrylamide an interesting candidate
for searches in the interstellar medium. In addition, a tentative
detection of the related molecule propionamide (C2H5C(O)NH2) has
been recently claimed toward Sgr B2(N).
The aim of this work is to extend the knowledge of the laboratory
rotational spectrum of acrylamide to higher frequencies, which would
make it possible to conduct a rigorous search for interstellar
signatures of this amide using millimeter wave astronomy.
We measured and analyzed the rotational spectrum of acrylamide between
75 and 480GHz. We searched for emission of acrylamide in the imaging
spectral line survey ReMoCA performed with the Atacama Large
Millimeter/submillimeter Array toward Sgr B2(N). We also searched for
propionamide in the same source. The astronomical spectra were
analyzed under the assumption of local thermodynamic equilibrium.
We report accurate laboratory measurements and analyses of thousands
of rotational transitions in the ground state and two excited
vibrational states of the most stable syn form of acrylamide. In
addition, we report an extensive set of rotational transitions for the
less stable skew conformer. Tunneling through a low energy barrier
between two symmetrically equivalent configurations has been revealed
for this higher-energy species. Neither acrylamide nor propionamide
were detected toward the two main hot molecular cores of Sgr B2(N). We
did not detect propionamide either toward a position located to the
east of the main hot core, thereby undermining the recent claim of its
interstellar detection toward this position. We find that acrylamide
and propionamide are at least 26 and 14 times less abundant,
respectively, than acetamide toward the main hot core Sgr B2(N1S), and
at least 6 and 3 times less abundant, respectively, than acetamide
toward the secondary hot core Sgr B2(N2).
A comparison with results of astrochemical kinetics model for related
species suggests that acrylamide may be a few hundred times less
abundant than acetamide, corresponding to a value that is at least an
order of magnitude lower than the observational upper limits.
Propionamide may be as little as only a factor of two less abundant
than the upper limit derived toward Sgr B2(N1S). Lastly, the
spectroscopic data presented in this work will aid future searches of
acrylamide in space.
Description:
Observed rotational transitions of syn and skew conformers of
acrylamide.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 106 9725 List of the measured transitions of syn acrylamide
tablea4.dat 106 5024 List of the measured transitions of skew acrylamide
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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- 5 A5 --- VibState Vibrational state
8- 10 I3 --- J' Upper state J quantum number
11- 13 I3 --- Ka' Upper state Ka quantum number
14- 16 I3 --- Kc' Upper state Kc quantum number
19- 21 I3 --- J" Lower state J quantum number
22- 24 I3 --- Ka" Lower state Ka quantum number
25- 27 I3 --- Kc" Lower state Kc quantum number
40- 50 F11.4 MHz FreqObs Observed transition frequency
53- 59 F7.4 MHz O-C Observed minus calculated frequency
62- 66 F5.3 MHz e_Freq Experimental uncertainty
69- 75 F7.4 MHz (O-C)b ? Observed minus calculated frequency
for blends
77- 80 F4.2 --- wb ? Weight of the components of the blends
85-106 A22 --- Notes Source of the data (G1)
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- J' Upper state J quantum number
4- 6 I3 --- Ka' Upper state Ka quantum number
7- 9 I3 --- Kc' Upper state Kc quantum number
10- 12 I3 --- v' Upper state v quantum number (1)
15- 17 I3 --- J" Lower state J quantum number
18- 20 I3 --- Ka" Lower state Ka quantum number
21- 23 I3 --- Kc" Lower state Kc quantum number
24- 26 I3 --- v" Lower state v quantum number (1)
40- 50 F11.4 MHz FreqObs Observed transition frequency
53- 59 F7.4 MHz O-C Observed minus calculated frequency
62- 66 F5.3 MHz e_Freq Experimental uncertainty
69- 75 F7.4 MHz (O-C)b ? Observed minus calculated frequency
for blends
77- 80 F4.2 --- wb ? Weight of the components of the blends
85-106 A22 --- Notes Source of the data (G1)
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Note (1): The vibrational quantum number v=0 corresponds to 0+ state and
v=1 to 0- state of the ground state tunneling doublet.
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Global notes:
Note (G1): Marstokk et al. (2000): 2000, J. Mol. Struct., 524, 69.
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Acknowledgements:
Lucie Kolesnikova, lucie.kolesnikova(at)vscht.cz
(End) L. Kolesnikova [UCT Prague, Czech Republic], P. Vannier [CDS] 02-Mar-2022