Accurate ab initio spectroscopic studies of promising interstellar ethanolamine iminic precursors
Context. The detection of NH2CH2CH2OH (ethanolamine) in molecular cloud G+0.693-0.027 adds an additional player to the pre-biotic molecules discovered so far in the interstellar medium (ISM). As this molecule might be formed through condensed-phase hydrogenation steps, detecting one or more of the molecules involved might help to elucidate the chemical pathway leading to its production. Aims. The chemical path involves the formation of four chemical species. In this work, we study the energies of the isomers involved, indicate the best candidates for detection purposes, and provide the distortion constants of the most energetically favoured isomers undetected so far. Methods. We used highly accurate CCSD(T)-F12/cc-pCVTZ-F12 computations to predict the lowest energy isomers as well as their spectroscopic constants, taking corrections for core electron correlation and scalar relativity into account. Results. We studied 14 isomers. We find that the lowest energy isomer proposed in previous studies is not the actual minimum. We provide a set of rotational and distortion constants of the two new most stable isomers together with their fundamental vibrational frequencies in order to guide the search for these important astrochemical precursors of prebiotic molecules in the ISM. © 2024 EDP Sciences. All rights reserved.
Formation pathways of formic acid (HCOOH) in regions with methanol ices
We modeled the collisions between OH+ projectiles with kinetic energies ranging from 10 to 22 eV and an amorphous cold (CH3OH)10 substrate using Born-Oppenheimer molecular dynamics (BOMD) simulations. We conducted the simulations for a collision time of 400 femtoseconds (fs), during which we followed multiple bond-forming and breaking reactions. Here, we report four new pathways for the formation of formic acid HCOOH. We find new precursors such as CH3(OH)+2 , HC(OH)+2 , CH2OH+, and CH2(OH)2, which are essential in these pathways for the formation of formic acid. The methanodiol CH2(OH)2 and hydroxymethyl CH2OH+ cations have previously been identified as key precursors of formaldehyde. These pathways suggest new ways to form formic acid in methanol ice mantles on dust grains, offering alternative mechanisms leading to the formation of complex organic molecules (COMs) in space.
A Search for Cloud Cores Affected by Shocked Carbon Chain Chemistry in L1251
We searched for shocked carbon chain chemistry (SCCC) sources with C3S abundances surpassing those of HC5N toward the dark cloud L1251, using the Effelsberg telescope at the K band (18-26 GHz). L1251-1 and L1251-3 are identified as the most promising SCCC sources. The two sources harbor young stellar objects. We conducted mapping observations toward L1251-A, the western tail of L1251, at λ ∼ 3 mm with the Purple Mountain Observatory 13.7 m and the Nobeyama Radio Observatory 45 m telescopes in lines of C2H, N2H+, CS, HCO+, SO, HC3N, and C18O as well as in CO 3-2 using the James Clerk Maxwell Telescope (JCMT). The spectral data were combined with archival data including Spitzer and Herschel continuum maps for further analysis. Filamentary substructures labeled as F1-F6 were extracted in L1251, with F1 being associated with L1251-A hosting L1251-1. The peak positions of dense gas traced by HCO+ are misaligned relative to those of the dust clumps. Episodic outflows are common in this region. The twisted morphology of F1 and velocity distribution along L1251-A may originate from stellar feedback. SCCC in L1251-1 may have been caused by outflow activities originated from the infrared source IRS1. The signposts of ongoing SCCC and the broadened line widths of C3S and C4H in L1251-1 as well as the distribution of HC3N are also related to outflow activities in this region. L1251-1 (IRS1) together with the previously identified SCCC source IRS3 demonstrate that L1251-A is an excellent region to study SCCC.