Photodetachment cross sections of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mi>n</mml:mi></mml:mrow></mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:msup><mml:mrow /><mml:mo>−</mml:mo></mml:msup><mml:mi> </mml:mi><mml:mo>(</mml:mo><mml:mi>n</mml:mi><mml:mo>=</mml:mo><mml:mn>1</mml:mn><mml:mi>–</mml:mi><mml:mn>3</mml:mn><mml:mo>)</mml:mo></mml:math>hydrocarbon-chain anions

Douguet, Nicolas; Kokoouline, Viatcheslav; Orel, A. E.

doi:10.1103/physreva.90.063410

Cited by 15 publications

(17 citation statements)

References 48 publications

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“…Using a typical value of 4 eV for electronic affinity of carbon chain molecules C 2n H and C 2n−1 N (n is an integer) and assuming a small energy of the incident electron, we obtain 13 < V 0 < 16. Our calculated values of β 0 are 0.19 (CN), 0.46 (C 2 H), 0.56 (C 4 H) and 0.39 (C 6 H) [23]. The latter value, corresponding to the 2 Π ground state of C 6 H, was calculated at the Hartree-Fock level, and could be somewhat underestimated.…”

Section: The Indirect Rea In Larger Moleculesmentioning

confidence: 90%

“…For instance, the Franck-Condon integral in Eq. (5) is about 0.90 for C 2 H/C 2 H − and 0.87 for C 4 H/C 4 H − [23]. For transitions to other vibrational levels, the integral is significantly smaller.…”

Section: Direct Mechanism Of Radiative Electron Attachment To Cnmentioning

confidence: 93%

“…The only difference between the normal coordinates of M and M − , which will be accounted for below in evaluating the Franck-Condon overlaps, is the displacement between the equilibrium positions of M and M − . Note that this approximation is not only convenient, but has been shown numerically to be excellent for CN [18], as well as for the hydrocarbon chains C 2 H, C 4 H and C 6 H [23].…”

Section: The Indirect Rea In Larger Moleculesmentioning

confidence: 99%

“…For molecules such as C n H and C m N, for which the potential energy surfaces of the initial electronic state of the target and the final state of the negative ion are quite similar in shape near the equilibrium positions of the ion and the neutral molecule [23], the Franck-Condon integral in Eq. (5) is the largest for transitions with v f = v, for which its value is close to unity.…”

Section: Direct Mechanism Of Radiative Electron Attachment To Cnmentioning

confidence: 99%

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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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Section: The Indirect Rea In Larger Moleculesmentioning

confidence: 90%

Section: Direct Mechanism Of Radiative Electron Attachment To Cnmentioning

confidence: 93%

Section: The Indirect Rea In Larger Moleculesmentioning

confidence: 99%

Section: Direct Mechanism Of Radiative Electron Attachment To Cnmentioning

confidence: 99%

See 2 more Smart Citations

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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“…The analytical model used in the theoretical treatment of the process is described in ref. [209]. It should be stressed here that the model does not account for possible rovibrational resonances that could be present in the photodetachment spectrum.…”

Section: Electron-molecule Collisionsmentioning

confidence: 99%

Uncertainty estimates for theoretical atomic and molecular data

Chung¹,

Braams²,

Bartschat³

et al. 2016

J. Phys. D: Appl. Phys.

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Sources of uncertainty are reviewed for calculated atomic and molecular data that are important for plasma modeling: atomic and molecular structure and cross sections for electron-atom, electron-molecule, and heavy particle collisions. We concentrate on model uncertainties due to approximations to the fundamental many-body quantum mechanical equations and we aim to provide guidelines to estimate uncertainties as a routine part of computations of data for structure and scattering.

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Negative Ions in Space

Millar¹,

Walsh

Field³

2017

Chem. Rev.

215

164

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Until a decade ago, the only anion observed to play a prominent role in astrophysics was H. The bound-free transitions in H dominate the visible opacity in stars with photospheric temperatures less than 7000 K, including the Sun. The H anion is also believed to have been critical to the formation of molecular hydrogen in the very early evolution of the Universe. Once H formed, about 500 000 years after the Big Bang, the expanding gas was able to lose internal gravitational energy and collapse to form stellar objects and "protogalaxies", allowing the creation of heavier elements such as C, N, and O through nucleosynthesis. Although astronomers had considered some processes through which anions might form in interstellar clouds and circumstellar envelopes, including the important role that polycyclic aromatic hydrocarbons might play in this, it was the detection in 2006 of rotational line emission from CH that galvanized a systematic study of the abundance, distribution, and chemistry of anions in the interstellar medium. In 2007, the Cassini mission reported the unexpected detection of anions with mass-to-charge ratios of up to ∼10 000 in the upper atmosphere of Titan; this observation likewise instigated the study of fundamental chemical processes involving negative ions among planetary scientists. In this article, we review the observations of anions in interstellar clouds, circumstellar envelopes, Titan, and cometary comae. We then discuss a number of processes by which anions can be created and destroyed in these environments. The derivation of accurate rate coefficients for these processes is an essential input for the chemical kinetic modeling that is necessary to fully extract physics from the observational data. We discuss such models, along with their successes and failings, and finish with an outlook on the future.

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Photodetachment cross sections of theC2nH− (n=1–3)hydrocarbon-chain anions

Cited by 15 publications

References 48 publications

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

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

Uncertainty estimates for theoretical atomic and molecular data

Negative Ions in Space

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