Astronomical identification of CN<sup>-</sup>, the smallest observed molecular anion

Agúndez, M.; Cernicharo, J.; Guèlin, M.; Kahane, C.; Roueff, E.; Kłos, Jacek; Aoiz, F. J.; Lique, François; Marcelino, N.; Goicoechea, J. R.; García, M. González; Gottlieb, C. A.; McCarthy, Michael; Thaddeus, P.

doi:10.1051/0004-6361/201015186

Cited by 227 publications

(186 citation statements)

References 27 publications

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“…In this case we did not observe the formation of formamide, but instead observed either the formation of protonated aminomethanol or formation of NH 2 CH + 2 . This molecule has not yet been observed, but it may be the precursor of the formation of other species observed: (1) CH 2 NH (observed in 1973; Godfrey et al 1973) through a dissociative recombinant process; and (2) NH 2 CH 2 CN (observed in 2008; Belloche et al 2008) by reacting with the anion, CN − , also detected recently (Agundez et al 2010). …”

Section: Discussionmentioning

confidence: 79%

Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

Spezia

Jeanvoine

Hase

et al. 2016

ApJ

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We show, by means of direct dynamics simulations, how it is possible to define possible reactants and mechanisms leading to the formation of formamide in the interstellar medium. In particular, different ion-molecule reactions in the gas phase were considered: NH 3 OH + , NH 2 OH + 2 , H 2 COH + , and NH 4 + for the ions and NH 2 OH, H 2 CO, and NH 3 for the partner neutrals. These calculations were combined with high level ab initio calculations to investigate possible further evolution of the products observed. In particular, for formamide, we propose that the NH 2 OH + 2 + H 2 CO reaction can produce an isomer, NH 2 OCH + 2 , that, after dissociative recombination, can produce neutral formamide, which was observed in space. The direct dynamics do not pre-impose any reaction pathways and in other reactions, we did not observe the formation of formamide or any possible precursor. On the other hand, we obtained other interesting reactions, like the formation of NH 2 CH + 2 . Finally, some radiative association processes are proposed. All of the results obtained are discussed in light of the species observed in radioastronomy.

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Section: Discussionmentioning

confidence: 79%

Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

Spezia

Jeanvoine

Hase

et al. 2016

ApJ

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“…The advantage of the anion photoexcitation method is that PE spectra contain signatures of any nonadiabatic dynamics, which are more difficult to observe in conventional electron attachment. For C 18 H 11 -we show that photoexcitation up to at least 1.5 eV above-threshold is almost exclusively converted back to the ground electronic state of the anion. Further, photodetachment of the anion is shown to be very inefficient compared with photoexcitation and ground electronic state anion recovery, implying a resilience to direct UV-induced electron loss.…”

Section: Introductionmentioning

confidence: 77%

Internal conversion outcompetes autodetachment from resonances in the deprotonated tetracene anion continuum

Bull

West

Verlet

2015

Phys. Chem. Chem. Phys.

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Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Internal conversion outcompetes autodetachment from resonances in the deprotonated tetracene anion continuumJames N. Bull a , Christopher W. West a and Jan R. R. Verlet a † Photoelectron velocity-map imaging and electronic structure calculations have been used to study the temporary anion (resonance) dynamics of the closed-shell site-specific deprotonated tetracene anion (C18H11 -) in the hv = 3.26 eV (380 nm) to 4.13 eV (300 nm) range. In accord with a recent frequency-, angle-, and time-resolved photoelectron imaging study on a related but open-shell polyaromatic radical anion (Chem. Sci., 2015, 6, 1578-1589, population of π*-resonances situated in the detachment continuum efficiently recover the ground electronic state of the anion through ultrafast non-adiabatic dynamics, followed by characteristic statistical electron loss (thermionic emission). The combined electron yield of direct photodetachment and autodetachment from the optically-accessed resonances in C18H11 -is several orders of magnitude smaller than thermionic emission from the ground electronic electronic state in the photon energy range studied. This result implies a resiliance to prompt photoejection from UV radiation, and the ability of neutral PAH-like species to capture a free electron and form a long-lived molecular anion that ultimately decays by thermionic emission on a millisecond timescale. The attachment mechanism applies to polyaromatic species that cannot support dipole-bound states, and may provide an additional route to forming anions in astrochemical environments. IntroductionPolyaromatic hydrocarbon (PAH) molecules are found across a diverse range of chemical environments. For example, they form as products in combustion and anthropogenic pollution, 1 they are used in new generation semiconductors and microelectronics, 2,3 and they have been postulated to be present in astrochemical environments. 4,5 In astrochemistry, anions are recognised as important chemical species, [6][7][8][9][10][11] and have been identified as small polyynes such as C 4 H -and C 6 H -, [12][13][14][15][16][17][18] and are commonly postulated to be present as PAHs. However, the detailed formation mechanism of astrochemical anions is unclear. It is commonly postulated that stable anions may be formed via electric dipole-bound doorway states; 19,20 however, most neutral PAH molecules do not have a sufficient dipole moment to support such a mechanism.Most molecules,...

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

Cited by 227 publications

References 27 publications

Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

Internal conversion outcompetes autodetachment from resonances in the deprotonated tetracene anion continuum

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

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Astronomical identification of CN-, the smallest observed molecular anion

Cited by 227 publications

References 27 publications

Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

Synthesis of Formamide and Related Organic Species in the Interstellar Medium via Chemical Dynamics Simulations

Internal conversion outcompetes autodetachment from resonances in the deprotonated tetracene anion continuum

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

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