Interstellar nitrile anions: Detection of C3N- and C5N- in TMC-1

Abstract

We report on the first detection of C3N- and C5N- towards the cold dark core TMC-1 in the Taurus region, using the Yebes 40 m telescope. The observed C3N/C3N- and C5N/C5N- abundance ratios are 140 and 2, respectively; that is similar to those found in the circumstellar envelope of the carbon-rich star IRC+10216. Although the formation mechanisms for the neutrals are different in interstellar (ion-neutral reactions) and circumstellar clouds (photodissociation and radical-neutral reactions), the similarity of the C3N/C3N- and C5N/C5N- abundance ratios strongly suggests a common chemical path for the formation of these anions in interstellar and circumstellar clouds. We discuss the role of radiative electronic attachment, reactions between N atoms and carbon chain anions Cn-, and that of H- reactions with HC3N and HC5N as possible routes to form CnN-. The detection of C5N- in TMC-1 gives strong support for assigning to this anion the lines found in IRC+10216, as it excludes the possibility of a metal-bearing species, or a vibrationally excited state. New sets of rotational parameters have been derived from the observed frequencies in TMC-1 and IRC+10216 for C5N- and the neutral radical C5N.

Accepted for publication in A&A Letters

References in corpus (6)

• Detection of C5N- and vibrationally excited C6H in IRC +10216
• New molecules in IRC+10216: confirmation of C${}_5$S and tentative identification of MgCCH, NCCP, and SiH${}_3$CN
• Detection of circumstellar CH2CHCN, CH2CN, CH3CCH and H2CS
• Search for anions in molecular sources: C4H- detection in L1527
• The Effects of Molecular Anions on the Chemistry of Dark Clouds
• Discovery of Time Variation of the Intensity of Molecular Lines in IRC+10216 in The Submillimeter and Far Infrared Domains

Cited by in corpus (29)

• Pure hydrocarbon cycles in TMC-1: Discovery of ethynyl cyclopropenylidene, cyclopentadiene and indene
• Discovery of benzyne, o-C6H4, in TMC-1 with the QUIJOTE line survey
• TMC-1, the starless core sulfur factory: Discovery of NCS, HCCS, H2CCS, H2CCCS, and C4S and detection of C5S
• Discovery of HC4NC in TMC-1: A study of the isomers of HC3N, HC5N, and HC7N
• Discovery of the propargyl radical (CH2CCH) in TMC-1: one of the most abundant radicals ever found and a key species for cyclization to benzene in cold dark clouds
• Discovery of HC3O+ in space: The chemistry of O-bearing species in TMC-1
• Space and laboratory discovery of HC3S+
• O-bearing complex organic molecules at the cyanopolyyne peak of TMC-1: detection of C2H3CHO, C2H3OH, HCOOCH3, and CH3OCH3
• Discovery of CH2CHCCH and detection of HCCN, HC4N, CH3CH2CN, and, tentatively, CH3CH2CCH in TMC-1
• The sulphur saga in TMC-1: Discovery of HCSCN and HCSCCH
• Discovery of the C7N- anion in TMC-1 and IRC+10216
• Carbon-Chain Chemistry in the Interstellar Medium
• Discovery of the acetyl cation, CH3CO+, in space and in the laboratory
• The magnesium paradigm in IRC+10216: Discovery of MgC${}_4$H${}^{+}$, MgC${}_3$N${}^{+}$, MgC${}_6$H${}^{+}$, and MgC${}_5$N${}^{+}$
• A study of C4H3N isomers in TMC-1: line by line detection of HCCCH2CN
• Astronomical Detection of the Interstellar Anion C10H- towards TMC-1 from the GOTHAM Large Program on the GBT
• Discovery of C5H+ and detection of C3H+ in TMC-1 with the QUIJOTE line survey
• Space and laboratory observation of the deuterated cyanomethyl radical HDCCN
• The abundance and excitation of molecular anions in interstellar clouds
• Discovery of two metallic cyanoacetylides in IRC+10216: HMgCCCN and NaCCCN
• Laboratory and astronomical discovery of cyanothioketene, NCCHCS, in the cold starless core TMC-1
• Discovery of interstellar 3-cyano propargyl radical, CH2CCCN
• Detection of deuterated methylcyanoacetylene, CH${}_2$DC${}_3$N, in TMC-1
• Doubly substituted isotopologues of HCCCN in TMC-1: Detection of D13CCCN, DC13CCN, DCC13CN, DCCC15N, H13C13CCN, H13CC13CN, HC13C13CN, HCC13C15N, and HC13CC15N
• Laboratory rotational spectroscopy and astronomical search of ethynyl substituted naphthalene
• Chemical variations across the TMC-1 boundary: molecular tracers from translucent phase to dense phase
• Laboratory observation and astronomical search of 1-cyano propargyl radical, HCCCHCN
• On the spectroscopy of phosphaalkynes: Millimeter- and submillimeter wave study of C2H5CP
• High-level ab initio quartic force fields and spectroscopic characterization of C${}_2$N${}^{-}$