Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH3CN and H2O:CH3CN ices

Bulak, M.; Paardekooper, D.M.; Fedoseev, G.; Linnartz, H.

doi:10.1051/0004-6361/202039695

Cited by 29 publications

(28 citation statements)

References 92 publications

(109 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is consistent with the UV photo-dissociation of gas phase acetonitrile for which C-C bond breaking is observed (Moriyama et al 1998;Kanda et al 1999). HCN and CH 4 are observed as major photo-products in VUV photolysis experiments of pure CH 3 CN ice at 20 K (Bulak et al 2021) and 12 K (Hudson & Moore 2004). Accordingly, we attributed the masses 16 and 27 to CH 4 and HCN photodesorption respectively.…”

Section: Pure Acetonitrile Icesupporting

confidence: 87%

Photodesorption of acetonitrile CH3CN in UV-irradiated regions of the Interstellar Medium: an experimental evidence

Basalgète,

Ocaña,

Féraud

et al. 2021

Preprint

View full text Add to dashboard Cite

Pure acetonitrile (CH 3 CN) and mixed CO:CH 3 CN and H 2 O:CH 3 CN ices have been irradiated at 15 K with Vacuum UltraViolet (VUV) photons in the 7-13.6 eV range using synchrotron radiation. VUV photodesorption yields of CH 3 CN and of photo-products have been derived as a function of the incident photon energy. The coadsorption of CH 3 CN with CO and H 2 O molecules, which are expected to be among the main constituents of interstellar ices, is found to have no significant influence on the VUV photodesorption spectra of CH 3 CN, CHCN•, HCN, CN• and CH 3 •. Contrary to what has generally been evidenced for most of the condensed molecules, these findings point toward a desorption process for which the CH 3 CN molecule that absorbs the VUV photon is the one desorbing. It can be ejected in the gas phase as intact CH 3 CN or in the form of its photo-dissociation fragments. Astrophysical VUV photodesorption yields, applicable to different locations, are derived and can be incorporated into astrochemical modeling. They vary from 0.67(±0.33) × 10 −5 to 2.0(±1.0) × 10 −5 molecule/photon for CH 3 CN depending on the region considered, which is high compared to other organic molecules such as methanol. These results could explain the multiple detections of gas phase CH 3 CN in different regions of the interstellar medium and are well-correlated to astrophysical observations of the Horsehead nebula and of protoplanetary disks (such as TW Hya and HD 163296).

show abstract

Section: Pure Acetonitrile Icesupporting

confidence: 87%

Photodesorption of acetonitrile CH3CN in UV-irradiated regions of the Interstellar Medium: an experimental evidence

Basalgète,

Ocaña,

Féraud

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…HNCO itself can also form on the surface of interstellar ices via the reaction of CO and NH radicals (Fedoseev et al 2015). Another molecule put forward as a parent molecule for many N-bearing COMs is methyl cyanide (CH 3 CN; Bulak et al 2021), which may be produced via reactions of CH 3 and CN radicals in ices. One route for the formation of ethyl cyanide (C 2 H 5 CN) is thought to be a piecewise addition of its functional groups on dust grains (Belloche et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Complex organic molecules in low-mass protostars on Solar System scales

Nazari

Gelder

Dishoeck

et al. 2021

A&A

Self Cite

View full text Add to dashboard Cite

Context. The chemical inventory of planets is determined by the physical and chemical processes that govern the early phases of star formation. Nitrogen-bearing species are of interest as many provide crucial precursors in the formation of life-related matter. Aims. The aim is to investigate nitrogen-bearing complex organic molecules towards two deeply embedded Class 0 low-mass protostars (Perseus B1-c and Serpens S68N) at millimetre wavelengths with the Atacama Large Millimeter/submillimeter Array (ALMA). Next, the results of the detected nitrogen-bearing species are compared with those of oxygen-bearing species for the same and other sources. The similarities and differences are used as further input to investigate the underlying formation pathways. Methods. ALMA observations of B1-c and S68N in Band 6 (~1 mm) and Band 5 (~2 mm) are studied at ~0.5′′ resolution, complemented by Band 3 (~3 mm) data in a ~2.5′′ beam. The spectra are analysed for nitrogen-bearing species using the CASSIS spectral analysis tool, and the column densities and excitation temperatures are determined. A toy model is developed to investigate the effect of source structure on the molecular emission. Results. Formamide (NH2CHO), ethyl cyanide (C2H5CN), isocyanic acid (HNCO, HN13CO, DNCO), and methyl cyanide (CH3CN, CH2DCN, and CHD2CN) are identified towards the investigated sources. Their abundances relative to CH3OH and HNCO are similar for the two sources, with column densities that are typically an order of magnitude lower than those of oxygen-bearing species. The largest variations, of an order of magnitude, are seen for NH2CHO abundance ratios with respect to HNCO and CH3OH and do not correlate with the protostellar luminosity. In addition, within uncertainties, the nitrogen-bearing species have similar excitation temperatures to those of oxygen-bearing species (~100–300 K). The measured excitation temperatures are larger than the sublimation temperatures for the respective species. Conclusions. The similarity of most abundances with respect to HNCO for the investigated sources, including those of CH2DCN and CHD2CN, hints at a shared chemical history, especially the high D-to-H ratio in cold regions prior to star formation. However, some of the variations in abundances may reflect the sensitivity of the chemistry to local conditions such as temperature (e.g. NH2CHO), while others may arise from differences in the emitting areas of the molecules linked to their different binding energies in the ice. The excitation temperatures likely reflect the mass-weighted kinetic temperature of a gas that follows a power law structure. The two sources discussed in this work add to the small number of sources that have been subjected to such a detailed chemical analysis on Solar System scales. Future data from the James Webb Space Telescope will allow a direct comparison between the ice and gas abundances of both smaller and larger nitrogen-bearing species.

show abstract

“…The main product of the CH 3 CN photolysis is HCN molecules. Their preferable formation according to the path CH 3 CN→ CH + H + HCN was previously observed under the action of UV light [23], electron beam [20], and photon beam [22]. The HCN concentration after the first stage of the irradiation for 2 s is ~64% for CH 3 CN@CF 0.5 and ~57% for CH 3 CN@CF 0.3 , and it reduces to ~49% for CH 3 CN@CF 0.5 and ~47% for CH 3 CN@CF 0.3 after the 200-s exposure.…”

Section: Discussionmentioning

confidence: 84%

“…An increase of the photon energy to 42 eV allowed for additional registration of the signals from C 2 H 2 + , C 2 N + ions and a weak signal from N 2+ [20]. The ultraviolet (UV) irradiation of an H 2 O:CH 3 CN ice at 20 K yielded a large number of nitriles [23]. Experiments show that the mechanism of photolysis of acetonitrile depends on the energy and power of the exciting radiation as well as its chemical environment.…”

Section: Introductionmentioning

confidence: 99%

Photolysis of Fluorinated Graphites with Embedded Acetonitrile Using a White-Beam Synchrotron Radiation

et al. 2022

View full text Add to dashboard Cite

Fluorinated graphitic layers with good mechanical and chemical stability, polar C–F bonds, and tunable bandgap are attractive for a variety of applications. In this work, we investigated the photolysis of fluorinated graphites with interlayer embedded acetonitrile, which is the simplest representative of the acetonitrile-containing photosensitizing family. The samples were continuously illuminated in situ with high-brightness non-monochromatized synchrotron radiation. Changes in the compositions of the samples were monitored using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS N K-edge spectra showed that acetonitrile dissociates to form HCN and N2 molecules after exposure to the white beam for 2 s, and the latter molecules completely disappear after exposure for 200 s. The original composition of fluorinated matrices CF0.3 and CF0.5 is changed to CF0.10 and GF0.17, respectively. The highly fluorinated layers lose fluorine atoms together with carbon neighbors, creating atomic vacancies. The edges of vacancies are terminated with the nitrogen atoms and form pyridinic and pyrrolic units. Our in situ studies show that the photolysis products of acetonitrile depend on the photon irradiation duration and composition of the initial CFx matrix. The obtained results evaluate the radiation damage of the acetonitrile-intercalated fluorinated graphites and the opportunities to synthesize nitrogen-doped graphene materials.

show abstract

Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH₃CN and H₂O:CH₃CN ices

Cited by 29 publications

References 92 publications

Photodesorption of acetonitrile CH3CN in UV-irradiated regions of the Interstellar Medium: an experimental evidence

Photodesorption of acetonitrile CH3CN in UV-irradiated regions of the Interstellar Medium: an experimental evidence

Complex organic molecules in low-mass protostars on Solar System scales

Photolysis of Fluorinated Graphites with Embedded Acetonitrile Using a White-Beam Synchrotron Radiation

Contact Info

Product

Resources

About