Discovery of the Ubiquitous Cation NS⁺ in Space Confirmed by Laboratory Spectroscopy

Abstract

We report the detection in space of a new molecular species which has been characterized spectroscopically and fully identified from astrophysical data. The observations were carried out with the 30m IRAM telescopea. The molecule is ubiquitous as its =2→1 transition has been found in cold molecular clouds, prestellar cores, and shocks. However, it is not found in the hot cores of Orion-KL and in the carbon-rich evolved star IRC+10216. Three rotational transitions in perfect harmonic relation' = 2/3/5 have been identified in the prestellar core B1b. The molecule has a Σ electronic ground state and its=2→1 transition presents the hyperfine structure characteristic of a molecule containing a nucleus with spin 1. A careful analysis of possible carriers shows that the best candidate is NS. The derived rotational constant agrees within 0.3-0.7% with ab initio calculations. NS was also produced in the laboratory to unambiguously validate the astrophysical assignment. The observed rotational frequencies and determined molecular constants confirm the discovery of the nitrogen sulfide cation in space. The chemistry of NS and related nitrogen-bearing species has been analyzed by means of a time-dependent gas phase model. The model reproduces well the observed NS/NS abundance ratio, in the range 30-50, and indicates that NS is formed by reactions of the neutral atoms N and S with the cations SH and NH, respectively.

A sensitive λ 3 mm line survey of L483

“…The value of about 1000 given by these authors is probably too high as it is obtained from S 18 O, for which oxygen fractionation is important (Loison et al 2019b). In the case of NS + , the NS/NS + ratio has been found to be remarkably uniform, in the range 29-52, across different starless and protostellar cores (Cernicharo et al 2018).…”

“…Second, observations with ALMA have recently unveiled the existence of a hot corino (i.e., warm complex organic molecules concentrated around the protostar) in this source (Oya et al 2017; Jacobsen et al 2018). And third, single-dish observations indicate that L483 has an exceptionally rich chemical composition, as indicated by the recent discoveries of various new interstellar molecules: the radical HCCO (Agúndez et al 2015a), the protonated form of cyanogen (NCCN) and its metastable isomer CNCN (Agúndez et al 2015b, 2018b), the ion NS + (Cernicharo et al 2018), the radical NCO and the ion H 2 NCO + , which are precursors of isocyanid acid and its isomers (Marcelino et al 2018a), and the S-bearing radicals HCS and HSC (Agúndez et al 2018a). These chemical features make L483 an ideal target to carry out a line survey to study its chemical composition and evaluate a possible connection with evolutionary status.…”

Sustained oscillations in interstellar chemistry models

“…On the other hand, our chemical model includes an extended and detailed chemical network including 254 species, coupled by 4872 reactions taken from our previous studies (Roueff et al 2015;Cernicharo et al 2018). In particular, it includes A&A 643, A121 (2020)…”

Millimeter- and submillimeter-wave spectroscopy of thioformamide and interstellar search toward Sgr B2(N)

“…Several small sulfur compounds have recently been observed in the interstellar medium (ISM): HS 2 (Fuente et al 2017), NS + (Cernicharo et al 2018), HCS, and HSC (Agúndez et al 2018). To date, 23 sulfur derivatives have been detected or tentatively detected in the ISM, which means that the sulfur atom holds the fifth position after hydrogen, carbon, oxygen, and nitrogen atoms; see, for instance "Molecules in Space" 1 in the Cologne Database for Molecular Spectroscopy.…”