Spectral Line Surveys of Evolved Stars

Cernicharo, J.; Agúndez, M.; Guèlin, M.

doi:10.1017/s1743921311025014

Cited by 19 publications

(10 citation statements)

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“…The first observation of such species was made in 2006 . To date, only six molecular anions have been detected: namely the two types of carbon-chain anions C 2 n H – and C 2 n +1 N – . These anions can react with neutral species and contribute in the building of larger negative species as inferred, for example, in the ion-neutral models developed by Vuitton et al for the upper atmosphere of Titan.…”

Section: Introductionmentioning

confidence: 99%

Reaction of CN^– with F, Cl, O, and S Atoms: Attachment or Associative Detachment?

Khiri

Chambaud²

2015

J. Phys. Chem. A

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Highly correlated ab initio wave functions within the UCCSD(T)-F12 approach have been used to map the potential energy surfaces (PESs) describing the reactivity of the CN(-) (X(1)Σ(+)) anion with neutral atoms present in interstellar media (F, Cl, O, and S). With the H atom, for comparison, the reaction [CN(-)((1)Σ(+)) + H((2)S)] evolves along the PES of the X(2)Σ(+) electronic ground state of HCN(-) (or HNC(-)) until the crossing with the X(1)Σ(+) electronic ground state of HCN (or HNC), where electron detachment occurs. The process is rather similar to the two halogen atoms F and Cl, with some differences due to the larger electron affinity of the halogens, making possible the existence of ClCN(-) in a (2)Σ(+) state. The reaction of CN(-) with O and S atoms proceeds via a multistep mechanism. The lowest electronic state at long distance, the (3)Π state arising from the [CN(-)((1)Σ(+)) + O/S((3)P)] reaction channel, does not correlate with the X(1)Σ(+) ground state of the XCN(-) anion (X = O or S). This (3)Π state and its bent components cross at medium RXC (RXN) distances the X(1)Σ(+) ground state of XCN(-) or XNC(-), and at shorter distances the X(2)Π state of the neutral XCN or XNC where the extra electron can detach. With both O and S atoms, it is shown that the spin-orbit couplings can efficiently lead the [CN(-)((1)Σ(+)) + O/S((3)P)] reaction toward the stable X(1)Σ(+) ground state of XCN(-) and XNC(-).

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Section: Introductionmentioning

confidence: 99%

Reaction of CN^– with F, Cl, O, and S Atoms: Attachment or Associative Detachment?

Khiri

Chambaud²

2015

J. Phys. Chem. A

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“…The significance of molecular line surveys of CSEs has been recently addressed by Cernicharo et al (2011). CRL 2688 (egg nebula) is a bright bipolar PPN, and serves as an ideal target to study the details of transition from AGB to PN phases which are poorly understood because of the short evolutionary time scale.…”

Section: Abstract Stars: Agb and Post-agb -Line: Identification -Ismmentioning

confidence: 99%

A Molecular Line Survey of CRL 2688 at 1 mm and 3 mm Wavelengths

et al. 2012

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It is well established that circumstellar envelopes (CSEs) around evolved stars are active sites of molecular synthesis, and CSEs are one of the major sources of chemical enrichment in the interstellar space. The investigation of molecular compositions in CSEs is essential to understand the chemical evolution of the Galaxy. In order to study circumstellar chemistry in different environments, we have been systematically performing molecular line surveys of a sample of evolved stars from asymptotic giant branch (AGB) stars, proto-planetary nebulae (PPNs), to planetary nebulae (PNs). The dynamical time scales in different evolutionary stages can impose a time limit on the reaction time scales. Here we report our results for CRL 2688.

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“…The earliest discovery of a molecular anion in the ISM has occurred in the experiments of McCarthy et al 6 It was followed by the observation of the carbon chains of the type C 2n H − and C 2n+1 N − by Cernicharo's group. 7 They were found in the circumstellar envelope of a source labeled IRC+10210 and in other dark clouds like TMC1. The negative ion CN − has also been observed in DMCs, where its neutral counterpart, CN, was also detected by the same group.…”

Section: Introductionmentioning

confidence: 98%

Forming NCO^– in Dense Molecular Clouds: Possible Gas-Phase Chemical Paths From Quantum Calculations

2016

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The existence of NCO– anions in the interstellar medium (ISM) has been suggested and searched for over the years but without any formal definitive sighting of that molecule. We discuss in this work the possible formation of either NCO– directly or of NCO neutral as a precursor to NCO– formation by electron attachment. We follow simple, gas-phase chemical reactions for which the general features are obtained from accurate quantum calculations. The results are shedding some additional light on the likely presence of this anion in the ISM environment, drawing further information from the specific features of the considered reactions on the additional chemical options that exist for its formation.

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Spectral Line Surveys of Evolved Stars

Cited by 19 publications

References 50 publications

Reaction of CN^– with F, Cl, O, and S Atoms: Attachment or Associative Detachment?

Reaction of CN^– with F, Cl, O, and S Atoms: Attachment or Associative Detachment?

A Molecular Line Survey of CRL 2688 at 1 mm and 3 mm Wavelengths

Forming NCO^– in Dense Molecular Clouds: Possible Gas-Phase Chemical Paths From Quantum Calculations

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Spectral Line Surveys of Evolved Stars

Cited by 19 publications

References 50 publications

Reaction of CN– with F, Cl, O, and S Atoms: Attachment or Associative Detachment?

Reaction of CN– with F, Cl, O, and S Atoms: Attachment or Associative Detachment?

A Molecular Line Survey of CRL 2688 at 1 mm and 3 mm Wavelengths

Forming NCO– in Dense Molecular Clouds: Possible Gas-Phase Chemical Paths From Quantum Calculations

Contact Info

Product

Resources

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Reaction of CN^– with F, Cl, O, and S Atoms: Attachment or Associative Detachment?

Reaction of CN^– with F, Cl, O, and S Atoms: Attachment or Associative Detachment?

Forming NCO^– in Dense Molecular Clouds: Possible Gas-Phase Chemical Paths From Quantum Calculations