Geometry and Microwave Rotational Spectrum of the FC16O18O• Radical

Koucký, Jan; Kania, P.; Uhlíková, Tereza; Kolesníková, Lucie; Beckers, Helmut; Willner, Helge; Urban, Štěpán

doi:10.1021/jp4054549

Cited by 9 publications

(6 citation statements)

References 20 publications

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“…SPFIT/SPCAT program package (Pickett 1991) was used for the analysis. (b) Fixed to the ground state value which is usually a preferred constraint against the zero or poorly determined value (Urban & Sarka 1990;Koucký et al 2013). (c) Number of distinct frequency lines in the fit.…”

Section: Syn Conformermentioning

confidence: 99%

Laboratory rotational spectroscopy of acrylamide and a search for acrylamide and propionamide toward Sgr B2(N) with ALMA

Kolesníková

Беллоче

Koucký

et al. 2022

A&A

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Context. 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 (CH 2 CHC(O)NH 2 ) 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 (C 2 H 5 C(O)NH 2 ) has been recently claimed toward Sgr B2(N). Aims. 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. Methods. We measured and analyzed the rotational spectrum of acrylamide between 75 and 480 GHz. 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. Results. 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). Conclusions. 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.

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Section: Syn Conformermentioning

confidence: 99%

Laboratory rotational spectroscopy of acrylamide and a search for acrylamide and propionamide toward Sgr B2(N) with ALMA

Kolesníková

Беллоче

Koucký

et al. 2022

A&A

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“…SPFIT/SPCAT program package (Pickett 1991) was used for the analysis. (c) Fixed to the calculated value, which is usually a preferred constraint over the zero or poorly determined value (Urban & Sarka 1990; Koucký et al 2013). (d) Relative energy with respect to the global minimum, taking into account the zero-point energy (ZPE).…”

Section: Transmentioning

confidence: 99%

Millimeter wave spectrum and search for vinyl isocyanate toward Sgr B2(N) with ALMA

Vávra

Kolesníková

Беллоче

et al. 2022

A&A

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Context. The interstellar detections of isocyanic acid (HNCO), methyl isocyanate (CH 3 NCO), and very recently also ethyl isocyanate (C 2 H 5 NCO), open the question of the possible detection of vinyl isocyanate (C 2 H 3 NCO) in the interstellar medium. There are only low-frequency spectroscopic data (< 40 GHz) available for this species in the literature. This makes predictions at higher frequencies rather uncertain hampering its search in space by millimeter wave astronomy. Aims. The aim of the present study is, on one hand, to extend the laboratory rotational spectrum of vinyl isocyanate into the millimeter wave region and, on the other hand, to undertake a first check for its presence in the high-mass star forming region Sgr B2, where other isocyanates and a plethora of complex organic molecules are observed. Methods. The pure rotational spectrum of vinyl isocyanate was recorded in the frequency regions 127.5-218 and 285-330 GHz using the Prague millimeter wave spectrometer. The spectral analysis was supported by high-level quantum-chemical calculations. On the astronomy side, we assumed local thermodynamic equilibrium to compute synthetic spectra of vinyl isocyanate and to search for it in the ReMoCA survey performed with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the high-mass star forming protocluster Sgr B2(N). Additionally, we searched for the related molecule ethyl isocyanate in the same source.Results. Accurate values for the rotational and centrifugal distortion constants are reported for the ground vibrational states of trans and cis vinyl isocyanate from the analysis of more than 1000 transitions. We report nondetections of vinyl and ethyl isocyanate toward the main hot core of Sgr B2(N). We find that vinyl and ethyl isocyanate are at least 11 and 3 times less abundant than methyl isocyanate in this source, respectively. Conclusions. Although the precise formation mechanism of interstellar methyl isocyanate itself remains uncertain, we infer from existing astrochemical models that our observational upper limit for the CH 3 NCO:C 2 H 5 NCO ratio in Sgr B2(N) is consistent with ethyl isocyanate being formed on dust grains via the abstraction or photodissociation of an H atom from methyl isocyanate, followed by the addition of a methyl radical. The dominance of such a process for ethyl isocyanate production, combined with the absence of an analogous mechanism for vinyl isocyanate, would indicate that the ratio C 2 H 3 NCO:C 2 H 5 NCO should be rather less than unity. Even though vinyl isocyanate was not detected toward Sgr B2(N), results of this work represent a significant improvement on previous low-frequency studies and will allow the astronomical community to continue in searching for this species in the universe.

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“…The last two radicals appearing in Figure (right panel) are FCO 2 (top) and ClCH 2 (bottom), which are both planar with C 2 v symmetry. The best geometry reported in the literature for FCO 2 was obtained in ref , where both r 0 and r s structures were determined. The former can be compared with the present determination: our r 0 C–F and C–O bond lengths are 1.325(4) Å and 1.235(2) Å, respectively, which agree rather well with the values of 1.3204 and 1.2407 Å from ref , the differences being about 5 mÅ for both bond lengths.…”

Section: Resultsmentioning

confidence: 99%

“…The best geometry reported in the literature for FCO 2 was obtained in ref , where both r 0 and r s structures were determined. The former can be compared with the present determination: our r 0 C–F and C–O bond lengths are 1.325(4) Å and 1.235(2) Å, respectively, which agree rather well with the values of 1.3204 and 1.2407 Å from ref , the differences being about 5 mÅ for both bond lengths. Moving to the SE equilibrium structure, it is noted that the differences between r e (SE) and r e (SE) full are entirely negligible.…”

Section: Resultsmentioning

confidence: 99%

The Semiexperimental Approach at Work: Equilibrium Structure of Radical Species

Alessandrini,

Melosso,

Bizzocchi

et al. 2024

J. Phys. Chem. A

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The so-called semiexperimental (SE) approach is a powerful technique for obtaining highly accurate equilibrium structures for isolated systems. This Featured Article describes its extension to open-shell species, thus providing the first systematic investigation on radical equilibrium geometries to be used for benchmarking purposes. The small yet significant database obtained demonstrates that there is no reduction in accuracy when moving from closed-shell species to radicals. We also provide an extension of the applicability of the SE approach to medium-/ large-sized radicals by exploiting the so-called "Lego-brick" approach, which is based on the assumption that a molecular system can be seen as formed by smaller fragments for which the SE equilibrium structure is available. In this Featured Article we show that this model can be successfully applied also to open-shell species.

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Geometry and Microwave Rotational Spectrum of the FC¹⁶O¹⁸O^• Radical

Cited by 9 publications

References 20 publications

Laboratory rotational spectroscopy of acrylamide and a search for acrylamide and propionamide toward Sgr B2(N) with ALMA

Laboratory rotational spectroscopy of acrylamide and a search for acrylamide and propionamide toward Sgr B2(N) with ALMA

Millimeter wave spectrum and search for vinyl isocyanate toward Sgr B2(N) with ALMA

The Semiexperimental Approach at Work: Equilibrium Structure of Radical Species

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