417 research outputs found
Collisional broadening and hyperfine structure of rotational transitions. Reply to the comments on “A never-ending story in the sky: The secrets of chemical evolution”
We would like to thank all commentators for their insightful comments, all of them contributing to enrich and complement our review. Among them, the comments by Agúndez -Cernicharo [1], Hochlaf [2], and Feng -Gou [3] provided the opportunity to further extend the discussion
New quantum chemical computations of formamide deuteration support a gas-phase formation of this prebiotic molecule
Based on recent work, formamide might be a potentially very important
molecule in the emergence of terrestrial life. Although detected in the
interstellar medium for decades, its formation route is still debated, whether
in the gas phase or on the dust grain surfaces. Molecular deuteration has
proven to be, in other cases, an efficient way to identify how a molecule is
synthesised. For formamide, new published observations towards the
IRAS16293-2422 B hot corino show that its three deuterated forms have all the
same deuteration ratio, 2--5%, and that this is a factor 3--8 smaller than that
measured for H2CO towards the IRAS16293-2422 protostar. Following a previous
work on the gas-phase formamide formation via the reaction NH2 + H2CO -> HCONH2
+ H, we present here new calculations of the rate coefficients for the
production of monodeuterated formamide through the same reaction, starting from
monodeuterated NH2 or H2CO. Some misconceptions regarding our previous
treatment of the reaction are also cleared up. The results of the new
computations show that, at the 100 K temperature of the hot corino, the rate of
deuteration of the three forms is the same, within 20%. On the contrary, the
reaction between non-deuterated species proceeds three times faster than that
with deuterated ones. These results confirm that a gas-phase route for the
formation of formamide is perfectly in agreement with the available
observations.Comment: MNRAS in pres
Unveiling Bifunctional Hydrogen Bonding with the Help of Quantum Chemistry: The Imidazole-Water Adduct as Test Case
The ubiquitous role of water and its amphiprotic nature call for a deeper insight into the physical-chemical properties of hydrogen-bonded complexes formed with building blocks of biomolecules. In this work, the semiexperimental (SE) approach combined with the template model (TM) protocol allowed the accurate determination of the equilibrium structure of two isomeric forms of the imidazole-water complex. In this procedure, the integration of experiment (thanks to a recent rotational spectroscopy investigation) and theory is exploited, also providing the means of assessing the reliability and accuracy of different quantum-chemical approaches. Overall, this study demonstrated the robustness of the combined SE-TM approach, which can provide accurate results using affordable quantum-chemical methods. Finally, the structural and energetic characteristics of these complexes have been examined in detail and compared with those of analogous heterocycle-water adducts, also exploiting energy decomposition analyses
A twist on the reaction of the CN radical with methylamine in the interstellar medium: new hints from a state-of-the-art quantum-chemical study
Despite the fact that the majority of current models assume that interstellar
complex organic molecules (iCOMs) are formed on dust-grain surfaces, there is
some evidence that neutral gas-phase reactions play an important role. In this
paper, we investigate the reaction occurring in the gas phase between
methylamine (CHNH) and the cyano (CN) radical, for which only
fragmentary and/or inaccurate results have been reported to date. This case
study allows us to point out the pivotal importance of employing
quantum-chemical calculations at the state of the art. Since the two major
products of the CHNH + CN reaction, namely the CHNH and
CHNH radicals, have not been spectroscopically characterized yet, some
effort has been made for filling this gap.Comment: 14 pages, 6 figures, MNRAS in pres
Rotational Spectroscopy Meets Quantum Chemistry for Analyzing Substituent Effects on Non-Covalent Interactions: The Case of the Trifluoroacetophenone-Water Complex
The most stable isomer of the 1:1 complex formed by 2,2,2-trifluoroacetophenone and water has been characterized by combining rotational spectroscopy in supersonic expansion and state-of-the-art quantum-chemical computations. In the observed isomer, water plays the double role of proton donor and acceptor, thus forming a seven-membered ring with 2,2,2-trifluoroacetophenone. Accurate intermolecular parameters featuring one classical O-H···O hydrogen bond and one weak C-H···O hydrogen bond have been determined by means of a semi-experimental approach for equilibrium structure. Furthermore, insights on the nature of the established non-covalent interactions have been unveiled by means of different bond analyses. The comparison with the analogous complex formed by acetophenone with water points out the remarkable role played by fluorine atoms in tuning non-covalent interactions
Gas-phase identification of (Z)-1,2-ethenediol, a key prebiotic intermediate in the formose reaction
Prebiotic sugars are thought to be formed on primitive Earth by the formose reaction. However, their formation is not fully understood and it is plausible that key intermediates could have formed in extraterrestrial environments and subsequently delivered on early Earth by cometary bodies. 1,2-Ethenediol, the enol form of glycolaldehyde, represents a highly reactive intermediate of the formose reaction and is likely detectable in the interstellar medium. Here, we report the identification and first characterization of (Z)-1,2-ethenediol by means of rotational spectroscopy. The title compound has been produced in the gas phase by flash vacuum pyrolysis of bis-exo-5-norbornene-2,3-diol at 750 °C, through a retro-Diels-Alder reaction. The spectral analysis was guided by high-level quantum-chemical calculations, which predicted spectroscopic parameters in very good agreement with the experiment. Our study provides accurate spectral data to be used for searches of (Z)-1,2-ethenediol in the interstellar space
Hyperfine-Resolved Near-Infrared Spectra of HO
Huge efforts have recently been taken in the derivation of accurate compilations of rovibrational energies of water, one of the most important reference systems in spectroscopy. Such precision is desirable for all water isotopologues, although their investigation is challenged by hyperfine effects in their spectra. Frequency-comb locked noise-immune cavity-enhanced optical-heterodyne molecular spectroscopy (NICE-OHMS) allows for achieving high sensitivity, resolution, and accuracy. This technique has been employed to resolve the subtle hyperfine splittings of rovibrational transitions of HOin the near-infrared region. Simulation and interpretation of the HOsaturation spectra have been supported by coupled-cluster calculations performed with large basis sets and accounting for high-level corrections. Experimental O hyperfine parameters are found in excellent agreement with the corresponding computed values. The need of including small hyperfine effects in the analysis of HO spectra has been demonstrated together with the ability of the computational strategy employed for providing quantitative predictions of the corresponding parameters
Editorial: Frontiers in astronomy and space sciences: Rising stars
Editorial on the Research Topic Frontiers in astronomy and space sciences: Rising star
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