Formation of complex organic molecules in molecular clouds: acetaldehyde, vinyl alcohol, ketene, and ethanol via the "energetic" processing of C${}_2$H${}_2$ ice

Abstract

The simultaneous detection of organic molecules of the form C${}_2$H${}_{\text{n}}$O, such as ketene (CH${}_2$CO), acetaldehyde (CH${}_3$CHO), and ethanol (CH${}_3$CH${}_2$OH), toward early star-forming regions offers hints of shared chemical history. Several reaction routes have been proposed and experimentally verified under various interstellar conditions to explain the formation pathways involved. Most noticeably, the non-energetic processing of C${}_2$H${}_2$ ice with OH-radicals and H-atoms was shown to provide formation routes to ketene, acetaldehyde, ethanol, and vinyl alcohol (CH${}_2$CHOH) along the H${}_2$O formation sequence on grain surfaces. In this work, the non-energetic formation scheme is extended with laboratory measurements focusing on the energetic counterpart, induced by cosmic rays penetrating the H${}_2$O-rich ice mantle. The focus here is on the H${}^{+}$ radiolysis of interstellar C${}_2$H${}_2$:H${}_2$O ice analogs at 17 K. Ultra-high vacuum experiments were performed to investigate the 200 keV H${}^{+}$ radiolysis chemistry of predeposited C${}_2$H${}_2$:H${}_2$O ices, both as mixed and layered geometries. Fourier-transform infrared spectroscopy was used to monitor in situ newly formed species as a function of the accumulated energy dose (or H${}^{+}$ fluence). The infrared (IR) spectral assignments are further confirmed in isotope labeling experiments using H${}_2$${}^{18}$O. The energetic processing of C${}_2$H${}_2$:H${}_2$O ice not only results in the formation of (semi-) saturated hydrocarbons (C${}_2$H${}_4$ and C${}_2$H${}_6$) and polyynes as well as cumulenes (C${}_4$H${}_2$ and C${}_4$H${}_4$), but it also efficiently forms O-bearing COMs, including vinyl alcohol, ketene, acetaldehyde, and ethanol, for which the reaction cross-section and product composition are derived. A clear composition transition of the product, from H-poor to H-rich species, is observed as a function of the accumulated energy dose.

arXiv comment14 pages, 7 figures, 2 tables

References in corpus (37)

• Observations of the Icy Universe
• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• Testing grain-surface chemistry in massive hot-core regions
• Formation of complex organic molecules in cold objects: the role of gas phase reactions
• Detection of the simplest sugar, glycolaldehyde, in a solar-type protostar with ALMA
• Simulation of the Formation and Morphology of Ice Mantles on Interstellar Grains
• Astrochemistry During the Formation of Stars
• The ALMA-PILS survey: Isotopic composition of oxygen-containing complex organic molecules toward IRAS 16293-2422B
• Constraining the abundances of complex organics in the inner regions of solar-type protostars
• A cold complex chemistry toward the low-mass protostar B1-b: evidence for complex molecule production in ices
• Cometary Chemistry and the Origin of Icy Solar System Bodies, the view after Rosetta
• Laboratory formation of fullerenes from PAHs: Top-down interstellar chemistry
• Atom addition reactions in interstellar ice analogues
• The ALMA-PILS survey: Inventory of complex organic molecules towards IRAS 16293-2422 A
• An interferometric study of the low-mass protostar IRAS 16293-2422: small scale organic chemistry
• L1157-B1, a factory of complex organic molecules in a Solar-type star forming region
• Complex organic molecules in comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy): detection of ethylene glycol and formamide
• Formation and recondensation of complex organic molecules during protostellar luminosity outbursts
• The ALMA-PILS survey: First detections of ethylene oxide, acetone and propanal toward the low-mass protostar IRAS 16293-2422
• The molecular cloud lifecycle
• The formation of ethylene glycol and other complex organic molecules in star-forming regions
• The census of interstellar complex organic molecules in the Class I hot corino of SVS13-A
• Complex organic molecules in low-mass protostars on solar system scales -- I. Oxygen-bearing species
• Detection of glycolaldehyde towards the solar-type protostar NGC1333 IRAS2A
• The (impossible?) formation of acetaldehyde on the grain surfaces: insights from quantum chemical calculations
• Infrared spectra of complex organic molecules in astronomically relevant ice matrices. I. Acetaldehyde, ethanol, and dimethyl ether
• Reactive Desorption of CO Hydrogenation Products under Cold Pre-stellar Core Conditions
• First Abundance Measurement of Organic Molecules in the Atmosphere of HH 212 Protostellar Disk
• Formation of interstellar methanol ice prior to the heavy CO freeze-out stage
• Chemical complexity induced by efficient ice evaporation in the Barnard 5 molecular cloud
• Complex organic molecules in comets from remote-sensing observations at millimeter wavelengths
• Formation of complex molecules in translucent clouds: Acetaldehyde, vinyl alcohol, ketene, and ethanol via nonenergetic processing of C2H2 ice
• The hot core towards the intermediate mass protostar NGC7129 FIRS 2: Chemical similarities with Orion KL
• Oxygen atom reactions with C2H6, C2H4, and C2H2 in ices
• Formation of Acetaldehyde on CO-rich Ices
• Detection of Acetylene toward Cepheus A East with Spitzer
• Revisiting the reactivity between HCO and CH${}_3$ on interstellar grain surfaces

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• Hydrogenation of accreting C-atoms and CO molecules -- simulating ketene and acetaldehyde formation under dark and translucent cloud conditions
• Hunt for complex cyanides in protostellar ices with JWST: Tentative detection of CH${}_3$CN and C${}_2$H${}_5$CN
• CoCCoA: Complex Chemistry in hot Cores with ALMA. Selected oxygen-bearing species
• The Role of Acetylene in the Chemical Evolution of Carbon Complexity
• Formation of complex organic molecules on interstellar CO ices? Insights from computational chemistry simulations
• Infrared spectra of complex organic molecules in astronomically relevant ice mixtures. V. Methyl cyanide (acetonitrile)
• Acetaldehyde binding energies: a coupled experimental and theoretical study
• Radical Addition and H Abstraction Reactions in C2H2, C2H4 and C2H6: A Gateway for Ethyl and Vinyl Bearing Molecules in the Interstellar Medium
• Formation of S-bearing complex organic molecules in interstellar clouds via ice reactions with C2H2, HS, and atomic H
• A deep search for large complex organic species toward IRAS16293-2422 B at 3 mm with ALMA
• CoCCoA: Complex Chemistry in hot Cores with ALMA. The chemical evolution of acetone from ice to gas
• Binding energies of ethanol and ethylamine on interstellar water ices: synergy between theory and experiments
• Lyα irradiation of solid-state formamide
• In situ characterization of volatile and refractory hydrocarbons produced by UV photolysis of interstellar C${}_2$H${}_2$ ice
• Abundant hydrocarbons in a buried galactic nucleus with signs of carbonaceous grain and polycyclic aromatic hydrocarbon processing
• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- X. Chemical differentiation among the massive cores in G9.62+0.19