Electron-molecule chemistry and charging processes on organic ices and Titan’s icy aerosol surrogates

Pirim, Claire; Gann, R. D.; McLain, J. L.; Orlando, Thomas M.

doi:10.1016/j.icarus.2015.06.006

Cited by 6 publications

(5 citation statements)

References 76 publications

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“…As pointed out by Pirim et al, 59 the desorption of light fragments, such as H + in the present case, is a probe for determining molecular damage promoted by electron impact. As pointed out by Pirim et al, 59 the desorption of light fragments, such as H + in the present case, is a probe for determining molecular damage promoted by electron impact.…”

Section: Astrophysical Implicationssupporting

confidence: 52%

“…The H + ion is by far the most desorbed ion, since it contributes to almost 96% of the entire ESID spectrum at 2300 eV electron bombardment. As pointed out by Pirim et al, 59 the desorption of light fragments, such as H + in the present case, is a probe for determining molecular damage promoted by electron impact. The H + ion has the highest desorption probability and, therefore, dissociation channels on surface that may result in H + desorption will be best probed by ESID.…”

Section: Astrophysical Implicationssupporting

confidence: 52%

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Non-thermal ion desorption from an acetonitrile (CH₃CN) astrophysical ice analogue studied by electron stimulated ion desorption

Ribeiro

Almeida

Garcia-Basabe

et al. 2015

Phys. Chem. Chem. Phys.

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The incidence of high-energy radiation onto icy surfaces constitutes an important route for leading new neutral or ionized molecular species back to the gas phase in interstellar and circumstellar environments, especially where thermal desorption is negligible. In order to simulate such processes, an acetonitrile ice (CH3CN) frozen at 120 K is bombarded by high energy electrons, and the desorbing positive ions are analyzed by time-of-flight mass spectrometry (TOF-MS). Several fragment and cluster ions were identified, including the Hn=1-3(+), CHn=0-3(+)/NHn=0-1(+); C2Hn=0-3(+)/CHn=0-3N(+), C2Hn=0-6N(+) ion series and the ion clusters (CH3CN)n=1-2(+) and (CH3CN)n=1-2H(+). The energy dependence on the positive ion desorption yield indicates that ion desorption is initiated by Coulomb explosion following Auger electronic decay. The results presented here suggest that non-thermal desorption processes, such as desorption induced by electronic transitions (DIET) may be responsible for delivering neutral and ionic fragments from simple nitrile-bearing ices to the gas-phase, contributing to the production of more complex molecules. The derived desorption yields per electron impact may contribute to chemical evolution models in different cold astrophysical objects, especially where the abundance of CH3CN is expected to be high.

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Section: Astrophysical Implicationssupporting

confidence: 52%

Section: Astrophysical Implicationssupporting

confidence: 52%

Non-thermal ion desorption from an acetonitrile (CH₃CN) astrophysical ice analogue studied by electron stimulated ion desorption

Ribeiro

Almeida

Garcia-Basabe

et al. 2015

Phys. Chem. Chem. Phys.

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“…However, it may be possible that once formed, heavy ions fragment back to light ions in a top-down process. Pirim et al (2015) reported Hdesorption during lowenergy (3-15 eV) electron irradiation of tholin materials maintained at 130 K.…”

Section: Comparison To Observations and Other Modelsmentioning

confidence: 99%

Simulating the density of organic species in the atmosphere of Titan with a coupled ion-neutral photochemical model

Vuitton

Yelle

Klippenstein

et al. 2019

Icarus

165

362

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We present a one-dimensional coupled ion-neutral photochemical kinetics and diffusion model to study the atmospheric composition of Titan in light of new theoretical kinetics calculations and scientific findings from the Cassini-Huygens mission. The model extends from the surface to the exobase. The atmospheric background, boundary conditions, vertical transport and aerosol opacity are all constrained by the Cassini-Huygens observations. The chemical network includes reactions between hydrocarbons, nitrogen and oxygen bearing species. It takes into account neutrals and both positive and negative ions with masses extending up to about 100 u. We incorporate high-resolution isotopic photoabsorption and photodissociation cross sections for N 2 as well as new photodissociation branching ratios for CH 4 and C 2 H 2 . Ab initio transition state theory calculations are performed in order to estimate the rate coefficients and products for critical reactions.Main reactions of production and loss for neutrals and ions are quantitatively assessed and thoroughly discussed. The vertical distributions of neutrals and ions predicted by the model generally reproduce observational data, suggesting that for the small species most chemical processes in Titan's atmosphere and ionosphere are adequately described and understood; some differences are highlighted. Notable remaining issues include (i) the total positive ion density (essentially HCNH + ) in the upper ionosphere, (ii) the low mass negative ion densities (CN -, C 3 N -/C 4 H -) in the upper atmosphere, and (iii) the minor oxygen-bearing species (CO 2 , H 2 O) density in the stratosphere. Pathways towards complex molecules and the impact of aerosols (UV shielding, atomic and molecular hydrogen budget, nitriles heterogeneous chemistry and condensation) are evaluated in the model, along with lifetimes and solar cycle variations.

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“…185 Much of the focus on electron collisions with molecules on surfaces is concerned with the chemistry and processing that occurs on the surface induced by the electrons. 186 More relevant here is a recent investigation of low-energy electron impact on films of HCN, CH 3 CN, and NH 2 CH 2 CN deposited on graphite at 90−130 K. 187 Ejection of H − ions from the surface was observed by dissociative electron attachment. For these laboratory experiments, "low-energy" electrons generally have electron energies from ∼3 to ∼13 eV.…”

Section: Processes At Surfacesmentioning

confidence: 99%

Negative Ions in Space

Millar¹,

Walsh

Field³

2017

Chem. Rev.

206

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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Electron-molecule chemistry and charging processes on organic ices and Titan’s icy aerosol surrogates

Cited by 6 publications

References 76 publications

Non-thermal ion desorption from an acetonitrile (CH₃CN) astrophysical ice analogue studied by electron stimulated ion desorption

Non-thermal ion desorption from an acetonitrile (CH₃CN) astrophysical ice analogue studied by electron stimulated ion desorption

Simulating the density of organic species in the atmosphere of Titan with a coupled ion-neutral photochemical model

Negative Ions in Space

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Electron-molecule chemistry and charging processes on organic ices and Titan’s icy aerosol surrogates

Cited by 6 publications

References 76 publications

Non-thermal ion desorption from an acetonitrile (CH3CN) astrophysical ice analogue studied by electron stimulated ion desorption

Non-thermal ion desorption from an acetonitrile (CH3CN) astrophysical ice analogue studied by electron stimulated ion desorption

Simulating the density of organic species in the atmosphere of Titan with a coupled ion-neutral photochemical model

Negative Ions in Space

Contact Info

Product

Resources

About

Non-thermal ion desorption from an acetonitrile (CH₃CN) astrophysical ice analogue studied by electron stimulated ion desorption

Non-thermal ion desorption from an acetonitrile (CH₃CN) astrophysical ice analogue studied by electron stimulated ion desorption