scholarly journals The role of radiolysis in the modelling of C2H4O2 isomers and dimethyl ether in cold dark clouds

2020 ◽  
Vol 500 (3) ◽  
pp. 3414-3424
Author(s):  
Alec Paulive ◽  
Christopher N Shingledecker ◽  
Eric Herbst
Keyword(s):  
Gas Phase ◽  
Dimethyl Ether ◽  
Recent Observation ◽  
Cosmic Ray ◽  
Thermal Method ◽  
Dark Clouds ◽  
Ice Surface ◽  
Dust Grain ◽  
Complex Organic

ABSTRACT Complex organic molecules (COMs) have been detected in a variety of interstellar sources. The abundances of these COMs in warming sources can be explained by syntheses linked to increasing temperatures and densities, allowing quasi-thermal chemical reactions to occur rapidly enough to produce observable amounts of COMs, both in the gas phase, and upon dust grain ice mantles. The COMs produced on grains then become gaseous as the temperature increases sufficiently to allow their thermal desorption. The recent observation of gaseous COMs in cold sources has not been fully explained by these gas-phase and dust grain production routes. Radiolysis chemistry is a possible non-thermal method of producing COMs in cold dark clouds. This new method greatly increases the modelled abundance of selected COMs upon the ice surface and within the ice mantle due to excitation and ionization events from cosmic ray bombardment. We examine the effect of radiolysis on three C2H4O2 isomers – methyl formate (HCOOCH3), glycolaldehyde (HCOCH2OH), and acetic acid (CH3COOH) – and a chemically similar molecule, dimethyl ether (CH3OCH3), in cold dark clouds. We then compare our modelled gaseous abundances with observed abundances in TMC-1, L1689B, and B1-b.

scholarly journals Infrared spectra of complex organic molecules in astronomically relevant ice matrices

2018 ◽  
Vol 611 ◽  
pp. A35 ◽  
Author(s):  
J. Terwisscha van Scheltinga ◽  
N. F. W. Ligterink ◽  
A. C. A. Boogert ◽  
E. F. van Dishoeck ◽  
H. Linnartz
Keyword(s):  
Gas Phase ◽  
Dimethyl Ether ◽  
Organic Molecules ◽  
Laboratory Data ◽  
Laboratory Studies ◽  
Astronomical Data ◽  
Astronomical Observations ◽  
Circumstellar Gas ◽  
Complex Organic ◽  
Recent Laboratory

Context. The number of identified complex organic molecules (COMs) in inter- and circumstellar gas-phase environments is steadily increasing. Recent laboratory studies show that many such species form on icy dust grains. At present only smaller molecular species have been directly identified in space in the solid state. Accurate spectroscopic laboratory data of frozen COMs, embedded in ice matrices containing ingredients related to their formation scheme, are still largely lacking.Aim. This work provides infrared reference spectra of acetaldehyde (CH3CHO), ethanol (CH3CH2OH), and dimethyl ether (CH3OCH3) recorded in a variety of ice environments and for astronomically relevant temperatures, as needed to guide or interpret astronomical observations, specifically for upcoming James Webb Space Telescope observations.Methods. Fourier transform transmission spectroscopy (500–4000 cm−1/20–2.5 μm, 1.0 cm−1 resolution) was used to investigate solid acetaldehyde, ethanol and dimethyl ether, pure or mixed with water, CO, methanol, or CO:methanol. These species were deposited on a cryogenically cooled infrared transmissive window at 15 K. A heating ramp was applied, during which IR spectra were recorded until all ice constituents were thermally desorbed.Results. We present a large number of reference spectra that can be compared with astronomical data. Accurate band positions and band widths are provided for the studied ice mixtures and temperatures. Special efforts have been put into those bands of each molecule that are best suited for identification. For acetaldehyde the 7.427 and 5.803 μm bands are recommended, for ethanol the 11.36 and 7.240 μm bands are good candidates, and for dimethyl ether bands at 9.141 and 8.011 μm can be used. All spectra are publicly available in the Leiden Database for Ice.

scholarly journals Non-thermal desorption of complex organic molecules

2020 ◽  
Vol 634 ◽  
pp. A103
Author(s):  
E. Dartois ◽  
M. Chabot ◽  
A. Bacmann ◽  
P. Boduch ◽  
A. Domaracka ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Organic Molecules ◽  
Solid Phase ◽  
Bulk Composition ◽  
Cosmic Ray ◽  
Water Ice ◽  
Sputtering Yield ◽  
Sputtering Yields ◽  
Complex Organic

Aims. Methanol ice is embedded in interstellar ice mantles present in dense molecular clouds. We aim to measure the sputtering efficiencies starting from different ice mantles of varying compositions experimentally, in order to evaluate their potential impact on astrochemical models. The sputtering yields of complex organic molecules is of particular interest, since few mechanisms are efficient enough to induce a significant feedback to the gas phase. Methods. We irradiated ice film mixtures made of methanol and carbon dioxide of varying ratios with swift heavy ions in the electronic sputtering regime. We monitored the evolution of the infrared spectra as well as the species released to the gas phase with a mass spectrometer. Methanol (12C) and isotopically labelled 13C-methanol were used to remove any ambiguity on the measured irradiation products. Results. The sputtering of methanol embedded in carbon dioxide ice is an efficient process leading to the ejection of intact methanol in the gas phase. We establish that when methanol is embedded in a carbon-dioxide-rich mantle exposed to cosmic rays, a significant fraction (0.2–0.3 in this work) is sputtered as intact molecules. The sputtered fraction follows the time-dependent bulk composition of the ice mantle, the latter evolving with time due to the radiolysis-induced evolution of the bulk. If methanol is embedded in a carbon dioxide ice matrix, as the analyses of the spectral shape of the CO2 bending mode observations in some lines of sight suggest, the overall methanol sputtering yield is higher than if embedded in a water ice mantle. The sputtering is increased by a factor close to the dominant ice matrix sputtering yield, which is about six times higher for pure carbon dioxide ice when compared to water ice. These experiments are further constraining the cosmic-ray-induced ice mantle sputtering mechanisms important role in the gas-phase release of complex organic molecules from the interstellar solid phase.

scholarly journals Formation of complex organic molecules in cold objects: the role of gas-phase reactions

2015 ◽  
Vol 449 (1) ◽  
pp. L16-L20 ◽  
Author(s):  
Nadia Balucani ◽  
Cecilia Ceccarelli ◽  
Vianney Taquet
Keyword(s):  
Gas Phase ◽  
Organic Molecules ◽  
Gas Phase Reactions ◽  
Complex Organic

scholarly journals DISCOVERY OF THE METHOXY RADICAL, CH 3 O, TOWARD B1: DUST GRAIN AND GAS-PHASE CHEMISTRY IN COLD DARK CLOUDS

2012 ◽  
Vol 759 (2) ◽  
pp. L43 ◽  
Author(s):  
J. Cernicharo ◽  
N. Marcelino ◽  
E. Roueff ◽  
M. Gerin ◽  
A. Jiménez-Escobar ◽  
...  
Keyword(s):  
Gas Phase ◽  
Dark Clouds ◽  
Gas Phase Chemistry ◽  
Methoxy Radical ◽  
Dust Grain ◽  
Phase Chemistry

scholarly journals A twist on the reaction of the CN radical with methylamine in the interstellar medium: new hints from a state-of-the-art quantum-chemical study

2020 ◽  
Vol 496 (4) ◽  
pp. 4298-4310 ◽  
Author(s):  
Cristina Puzzarini ◽  
Zoi Salta ◽  
Nicola Tasinato ◽  
Jacopo Lupi ◽  
Carlo Cavallotti ◽  
...  
Keyword(s):  
Gas Phase ◽  
Quantum Chemical ◽  
State Of The Art ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Gas Phase Reactions ◽  
Neutral Gas ◽  
Dust Grain ◽  
Complex Organic

ABSTRACT Despite the fact that the majority of current models assume that interstellar complex organic molecules (iCOMs) are formed on dust–grain surfaces, there is some evidence that neutral gas-phase reactions play an important role. In this paper, we investigate the reaction occurring in the gas phase between methylamine (CH3NH2) and the cyano (CN) radical, for which only fragmentary and/or inaccurate results have been reported to date. This case study allows us to point out the pivotal importance of employing quantum-chemical calculations at the state of the art. Since the two major products of the CH3NH2 + CN reaction, namely the CH3NH and CH2NH2 radicals, have not been spectroscopically characterized yet, some effort has been made for filling this gap.

scholarly journals Contribution of pulsars to cosmic-ray positrons in light of recent observation of inverse-Compton halos

2020 ◽  
Vol 102 (2) ◽  
Author(s):  
Silvia Manconi ◽  
Mattia Di Mauro ◽  
Fiorenza Donato
Keyword(s):  
Recent Observation ◽  
Cosmic Ray ◽  
Inverse Compton

Complex Organic Molecules Formation in Space Through Gas Phase Reactions: A Theoretical Approach

2017 ◽  
Vol 836 (2) ◽  
pp. 240 ◽  
Author(s):  
Pilar Redondo ◽  
Carmen Barrientos ◽  
Antonio Largo
Keyword(s):  
Gas Phase ◽  
Theoretical Approach ◽  
Organic Molecules ◽  
Gas Phase Reactions ◽  
Complex Organic
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