Astronomical detection of C$\mathsf{_{4}H^-}$, the second interstellar anion

Cernicharo, J.; Guèlin, M.; Agúndez, M.; Kawaguchi, Kentarou; McCarthy, Michael; Thaddeus, P.

doi:10.1051/0004-6361:20077415

Cited by 266 publications

(230 citation statements)

References 18 publications

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“…Thus, CN − appears to be confined to the same outer envelope of IRC +10216 as are other molecular anions observed in this source (e.g. Cernicharo et al 2007;Thaddeus et al 2008;Cernicharo et al 2008). A column density of 5 × 10 12 cm −2 and a rotation temperature of 16 K were derived from a rotational diagram constructed with the velocity integrated intensities of the J = 2−1 and 3−2 lines given in Table 1, based on the assumption of a uniform source with a radius of 20 , which is typical of molecules distributed in the outer shell.…”

Section: Observations and Identification Of Cn −mentioning

confidence: 64%

“…The molecular anions detected so far in the interstellar and circumstellar gas are all fairly heavy linear carbon chains consisting of three or more carbon atoms, and with neutral counterparts with large electron affinities: C 4 H − , C 6 H − , C 8 H − , C 3 N − , and C 5 N − (McCarthy et al 2006;Cernicharo et al 2007;Brünken et al 2007a;Remijan et al 2007;Thaddeus et al 2008;Cernicharo et al 2008). The abundance of these anions relative to the neutral counterparts increases with both size and the electron affinity of the neutral molecule, as expected for formation by radiative electron attachment (Herbst & Osamura 2008).…”

Section: Introductionmentioning

confidence: 99%

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Astronomical identification of CN^-, the smallest observed molecular anion

Agúndez¹,

Cernicharo

Guèlin³

et al. 2010

A&A

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We present the first astronomical detection of a diatomic negative ion, the cyanide anion CN − , and quantum mechanical calculations of the excitation of this anion by means of collisions with para-H 2 . The anion CN − is identified by observing the J = 2−1 and J = 3−2 rotational transitions in the C-star envelope IRC +10216 with the IRAM 30-m telescope. The U-shaped line profiles indicate that CN − , like the large anion C 6 H − , is formed in the outer regions of the envelope. Chemical and excitation model calculations suggest that this species forms from the reaction of large carbon anions with N atoms, rather than from the radiative attachment of an electron to CN, as is the case for large molecular anions. The unexpectedly high abundance derived for CN − , 0.25% relative to CN, indicates that its detection in other astronomical sources is likely. A parallel search for the small anion C 2 H − remains inconclusive, despite the previous tentative identification of the J = 1−0 rotational transition. The abundance of C 2 H − in IRC +10216 is found to be vanishingly small, <0.0014% relative to C 2 H.

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Section: Observations and Identification Of Cn −mentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Astronomical identification of CN^-, the smallest observed molecular anion

Agúndez¹,

Cernicharo

Guèlin³

et al. 2010

A&A

Self Cite

227

179

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“…Six anions have been detected so far in the ISM: C 6 H − [1][2][3][4][5], C 4 H − [6], C 8 H − [7], C 3 N − [8], C 5 N − [2,5], and CN − [9]. The possibility for atomic anions, such as H − , to be formed in the ISM by REA was first suggested by McDowell [10] in 1961.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of radiative electron attachment to CN, C2H, and C4H radicals

Douguet

Santos

Raoult

et al. 2015

The Journal of Chemical Physics

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A first-principle theoretical approach to study the process of radiative electron attachment is developed and applied to the negative molecular ions CN − , C4H − , and C2H − . Among these anions, the first two have already been observed in the interstellar space. Cross sections and rate coefficients for formation of these ions by radiative electron attachment to the corresponding neutral radicals are calculated. For completeness of the theoretical approach, two pathways for the process have been considered: (i) A direct pathway, in which the electron in collision with the molecule spontaneously emits a photon and forms a negative ion in one of the lowest vibrational levels, and (ii) an indirect, or two-step pathway, in which the electron is initially captured through non-BornOppenheimer coupling into a vibrationally resonant excited state of the anion, which then stabilizes by radiative decay. We develop a general model to describe the second pathway and show that its contribution to the formation of cosmic anions is small in comparison to the direct mechanism. The obtained rate coefficients at 30 K are 7 × 10 −16 cm 3 /s for CN − , 7 × 10 −17 cm 3 /s for C2H − , and 2 × 10 −16 cm 3 /s for C4H − . These rates weakly depend on temperature between 10K and 100 K. The validity of our calculations is verified by comparing the present theoretical results with data from recent photodetachment experiments.

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“…2,3 Furthermore, they are perhaps building blocks of larger organic systems such as polycyclic aromatic hydrocarbons. C n H, [4][5][6][7] C n H − ͑n Յ 8͒, [8][9][10] and H 2 C n ͑n Յ 6͒ ͑Refs. 11-13͒ have been detected by their microwave transitions in many astronomical objects.…”

Section: Introductionmentioning

confidence: 99%

Higher energy electronic transitions of HC2n+1H+ (n=2–7) and HC2n+1H (n=4–7) in neon matrices

Fulara

Nagy

Garkusha

et al. 2010

The Journal of Chemical Physics

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Electronic absorption spectra of linear HC 2n+1 H + ͑n =2-7͒ were recorded in 6 K neon matrices following their mass-selective deposition. Four new electronic band systems are identified; the strongest Ẽ 2 ⌸ g/u ← X 2 ⌸ u/g lies in the UV and the second most intense C 2 ⌸ g/u ← X 2 ⌸ u/g is located in the visible range. The known Ã 2 ⌸ g/u ← X 2 ⌸ u/g absorption is an order of magnitude weaker than C 2 ⌸ g/u ← X 2 ⌸ u/g . Transitions to the B and D states are also discussed. The wavelengths of the HC 2n+1 H + ͑n =2-7͒ electronic systems obey a linear relation as a function of the size of the cations, similar to other carbon chains. The B 3 ⌺ u − ← X 3 ⌺ g − transition in the UV of neutral HC 2n+1 H ͑n =4-7͒ has also been identified upon photobleaching of the cations trapped in the matrices.

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Astronomical detection of C$\mathsf{_{4}H^-}$, the second interstellar anion

Cited by 266 publications

References 18 publications

Astronomical identification of CN^-, the smallest observed molecular anion

Astronomical identification of CN^-, the smallest observed molecular anion

Theoretical study of radiative electron attachment to CN, C2H, and C4H radicals

Higher energy electronic transitions of HC2n+1H+ (n=2–7) and HC2n+1H (n=4–7) in neon matrices

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Astronomical detection of C$\mathsf{_{4}H^-}$, the second interstellar anion

Cited by 266 publications

References 18 publications

Astronomical identification of CN-, the smallest observed molecular anion

Astronomical identification of CN-, the smallest observed molecular anion

Theoretical study of radiative electron attachment to CN, C2H, and C4H radicals

Higher energy electronic transitions of HC2n+1H+ (n=2–7) and HC2n+1H (n=4–7) in neon matrices

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Astronomical identification of CN^-, the smallest observed molecular anion

Astronomical identification of CN^-, the smallest observed molecular anion