Cryogenic Chemistry and Quantitative Non‐Thermal Desorption from Pure Methanol Ices: High‐Energy Electron versus X‐Ray Induced Processes

Torres-Díaz, Daniela; Basalgète, Romain; Bertin, M.; Fillion, J.-H.; Michaut, X.; Amiaud, L.; Lafosse, A.

doi:10.1002/cphc.202200912

Cited by 4 publications

(1 citation statement)

References 56 publications

(151 reference statements)

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“…Nonthermal desorption mechanisms have been proposed and are being currently investigated to account for their presence in the gas phase. These mechanisms include electron promoted desorption (Marchione & McCoustra 2016), X ray induced desorption (Torres-Díaz et al 2023;Kalvāns 2021), desorption induced by exothermic reactions (Garrod et al 2007;Vasyunin & Herbst 2013) and, notably, UV photodesorption (Öberg et al 2009;Cruz-Diaz et al 2017) and cosmic ray (CR) sputtering (Dartois et al 2017(Dartois et al , 2022Pino et al 2019). Overall, COMs are expected to be highly diluted in the ice mantles of dust grains and on many occasions their gas-phase concentrations should thus be given by the desorption rate of the dominant ice molecules.…”

Section: Introductionmentioning

confidence: 99%

Indene energetic processing in ice mantles in the interstellar medium

Maté,

Tanarro,

Peláez

et al. 2024

A&A

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Indene, a small PAH, has been detected in the gas phase in the cold dense cloud TMC-1. Due to the low temperature in the cloud, below indene condensation temperature, its presence in the ice mantles of dust grains is likely. The aim of this work is to study the stability of indene against the energetic processing by VUV photons or cosmic rays in the ice mantles of dense molecular clouds. Ice layers of pure indene or indene diluted in water ice were grown by vapor deposition on a cold surface held at 10 K, 100 K, or 140 K. The samples were processed with VUV photons (120 -180 nm) and 5 keV electrons and the destruction of indene was monitored by following the decay of the its absorption bands in the infrared (IR) spectrum. Finally, we recorded the mass spectra of the decomposition products sublimated by thermal programmed desorption of the processed samples.. Photolysis and radiolysis cross-sections, along with half-life energy doses for indene in the solid a form and diluted in water ice matrices at 10 K were derived. Ketones and alcohols were identified as the main processing products in indene and water-ice mixtures Dilution in water ice enhances the destruction rate of indene under energetic processing. The molecule is expected to survive for more than 10$^7$ yr in the ice mantles of grains in the interior dense clouds, but it will end up getting destroyed within the next few hundred years by the intense VUV field in the diffuse region at the edges of the cloud.

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Section: Introductionmentioning

confidence: 99%

Indene energetic processing in ice mantles in the interstellar medium

Maté,

Tanarro,

Peláez

et al. 2024

A&A

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Formation pathways of formic acid (HCOOH) in regions with methanol ices

Inostroza-Pino,

Emmanuel Godwin,

Mardones

et al. 2024

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We modeled the collisions between OH^+ projectiles with kinetic energies ranging from 10 to 22 eV and an amorphous cold (CH3OH)_10 substrate using Born-Oppenheimer molecular dynamics (BOMD) simulations. We conducted the simulations for a collision time of 400 femtoseconds (fs), during which we followed multiple bond-forming and breaking reactions. Here, we report four new pathways for the formation of formic acid HCOOH . We find new precursors such as CH3(OH)2+ HC(OH)2^+ CH2OH^+ and CH2(OH)2 which are essential in these pathways for the formation of formic acid. The methanodiol CH2(OH)2 and hydroxymethyl CH2OH^+ cations have previously been identified as key precursors of formaldehyde. These pathways suggest new ways to form formic acid in methanol ice mantles on dust grains, offering alternative mechanisms leading to the formation of complex organic molecules (COMs) in space.

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X-ray photo-desorption of NH₃ and N₂ from ammonia ices: Mechanisms and yields in protoplanetary disks

Torres-Díaz,

Basalgète,

Amiaud

et al. 2024

A&A

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Ammonia is detected both in the gas phase and in the ices of protoplanetary disks. However, its gas phase abundances are still difficult to reproduce via chemical modelling when only the thermal-, UV photon-, and cosmic ray-induced processes are considered. Among other non-thermal mechanisms, X-ray photo-desorption is a relevant pathway to maintaining a budget of molecules in the gas of disks. However, no quantitative data are available to constrain its efficiency in the case of ammonia-containing ices. We studied the desorption induced by soft X-rays from ammonia ices to determine the photo-desorption yields of neutral molecules that can be applied to the conditions of protoplanetary disks. We also aim to identify the desorption mechanisms at play. Pure ammonia ices were deposited at 23\,K or 75\,K and irradiated between 395\,eV and 435\,eV, with monochromatic synchrotron light. Desorption of neutral molecules and fragments was detected using a quadrupole mass spectrometer, calibrated to obtain desorption yields. These values were extrapolated and the spectrum of a protoplanetary disk was used to extract average astrophysical desorption yields. Photo-desorption from NH$_3$ ices is dominated by the desorption of neutral NH$_3$ and N$_2$ molecules. The desorption mechanism mostly involves the thermalisation of Auger electrons in the ice, although resonant phenomena also contribute near the N 1s ionisation edge. The NH$_3$ photo-desorption is independent of ice morphology and irradiation temperature. Contrary to desorption desorption is sensitive to the photon fluence received by the ice. Average photo-desorption yields derived using the TW Hya X-ray spectrum reveal that the NH$_3$ photo-desorption would be four to six times more efficient than that of H$_2$O. This could be at the origin of unexplained high NH$_3$/H$_2$O abundance ratios predicted in the disk around TW Hya. This result ought to be confirmed by the study of mixed water-ammonia ices.

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Cryogenic Chemistry and Quantitative Non‐Thermal Desorption from Pure Methanol Ices: High‐Energy Electron versus X‐Ray Induced Processes

Abstract: Supporting information for this article is given via a link at the end of the document.

Cited by 4 publications

References 56 publications

Indene energetic processing in ice mantles in the interstellar medium

Indene energetic processing in ice mantles in the interstellar medium

Formation pathways of formic acid (HCOOH) in regions with methanol ices

X-ray photo-desorption of NH₃ and N₂ from ammonia ices: Mechanisms and yields in protoplanetary disks

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Cryogenic Chemistry and Quantitative Non‐Thermal Desorption from Pure Methanol Ices: High‐Energy Electron versus X‐Ray Induced Processes

Abstract: Supporting information for this article is given via a link at the end of the document.

Cited by 4 publications

References 56 publications

Indene energetic processing in ice mantles in the interstellar medium

Indene energetic processing in ice mantles in the interstellar medium

Formation pathways of formic acid (HCOOH) in regions with methanol ices

X-ray photo-desorption of NH3 and N2 from ammonia ices: Mechanisms and yields in protoplanetary disks

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X-ray photo-desorption of NH₃ and N₂ from ammonia ices: Mechanisms and yields in protoplanetary disks