scholarly journals Reactivity in interstellar ice analogs: role of the structural evolution

2018 ◽  
Vol 614 ◽  
pp. A107 ◽  
Author(s):  
P. Ghesquière ◽  
A. Ivlev ◽  
J. A. Noble ◽  
P. Theulé
Keyword(s):  
Structural Changes ◽  
Organic Molecules ◽  
Structural Evolution ◽  
Bulk Water ◽  
Pore Collapse ◽  
Water Ice ◽  
Bulk Diffusivity ◽  
Diffusion Limited ◽  
Interstellar Ice ◽  
Complex Organic

Context. The synthesis of interstellar complex organic molecules in ice involves several types of reactions between molecules and/or radicals that are usually considered to be diffusion controlled. Aims. We aim to understand the coupling between diffusion and reactivity in the interstellar ice mantle using a model binary reaction in the diffusion-limited regime. Methods. We performed isothermal kinetic laboratory experiments on interstellar ice analogs at low temperatures, using the NH3:CO2:H2O model system where reactants NH3 and CO2 have a low reaction barrier and are diluted in a water-dominated ice. Results. We found that in the diffusion-limited regime, the reaction kinetics is not determined by the intrinsic bulk diffusivity of reactants. Instead, reactions are driven by structural changes evolving in amorphous water ice, such as pore collapse and crystallization. Diffusion of reactants in this case likely occurs along the surface of (tiny) cracks generated by the structural changes. Conclusions. The reactivity driven by the structural changes breaks the conventional picture of reactant molecules/radicals diffusing in a bulk water ice. This phenomenon is expected to lead to a dramatic increase in production rates of interstellar complex organic molecules in star-forming regions.

Photon and thermal processing of CH3NH2-bearing ices. Synthesis of prebiotic species at low temperature (such as formamide, ethylamine, and methylcyanide), and N-heterocycles during warm up.

2021 ◽  
Author(s):  
Héctor Carrascosa ◽  
Cristóbal González Díaz ◽  
Guillermo M. Muñoz Caro ◽  
Pedro C. Gómez ◽  
María Luz Sanz
Keyword(s):  
Vacuum Chamber ◽  
Organic Molecules ◽  
Solid Phase ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Quadrupole Mass ◽  
Warm Up ◽  
Methyl Cyanide ◽  
Interstellar Ice ◽  
Complex Organic

<p>Hexamethylentetramine has drawn a lot of attention due to its potential to produce prebiotic species. This work aims to gain a better understanding in the chemical processes concerning methylamine under astrophysically relevant conditions. In particular, this work deeps into the formation of N-heterocycles in interstellar ice analogs exposed to UV radiation, which may lead to the formation of prebiotic species.</p> <p>Experimental simulations of interstellar ice analogs were carried out in ISAC. ISAC is an ultra-high vacuum chamber equipped with a cryostat, where gas and vapour species are frozen forming ice samples. Infrared and ultraviolet spectroscopy were used to monitor the solid phase, and quadrupole mass spectrometry served to measure the composition of the gas phase. The variety of species detected after UV irradiation of ices containing  methylamine revealed the presence of 12 species which have been already detected in the ISM, being 4 of them typically classified as complex organic molecules: formamide (HCONH<sub>2</sub>), methyl cyanide (CH<sub>3</sub>CN), CH<sub>3</sub>NH and CH<sub>3</sub>CHNH. Warming up of the irradiated CH<sub>3</sub>NH<sub>2</sub>-bearing ice samples lead to the formation of trimethylentriamine (TMT), a N-heterocycle precursor of HMT, and the subsequent synthesis of HMT at temperatures above 230 K.</p>

Chemical mechanism for the decomposition of CH3NH2 and implications to interstellar glycine

2020 ◽  
Vol 501 (1) ◽  
pp. 1202-1214
Author(s):  
Diego N de Jesus ◽  
Jean M B A da Silva ◽  
Tatiane N Tejero ◽  
Gladson de Souza Machado ◽  
Neubi F Xavier ◽  
...  
Keyword(s):  
Spectroscopic Data ◽  
Transition State Theory ◽  
Organic Molecules ◽  
State Theory ◽  
Chemical Mechanism ◽  
Rate Coefficients ◽  
Interstellar Ice ◽  
Chemical Behaviour ◽  
Tunnelling Effects ◽  
Complex Organic

ABSTRACT Complex organic molecules from extraterrestrial source are expected to have contributed to the Early Earth chemistry. Methylamine (CH3NH2)has already been observed in the interstellar medium (ISM) and is generally related to the formation of glycine, although the latter has not been identified in the ISM yet. In this work, a chemical model for CH3NH2 was investigated, comprising twenty-eight reactions and including reactions involving NH3 and HOOC, aiming to understand the main routes for formation and decomposition of methylamine and also to infer about the chemical behaviour of glycine in the ISM. Calculations were performed at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ level and rate coefficients were calculated adopting the canonical variational transition state theory (CVTST), in the temperature range 100 to 4000 K, including tunnelling effects. Starting from HCN, the preferred pathway for methylamine formation is through consecutive hydrogenation steps, forming CH2N, CH2NH, and CH2NH2 intermediates. Considering the decomposition, dissociation into CH3 and NH2 is the most favourable step. NH3 and HCN are common compounds in interstellar ice analogues and react producing NH2 and CH2N through NH2NCH2 and H2NCH2N intermediates. The latter is proposed here and spectroscopic data for any future experimental investigation are given. Finally, an extension to the ISM glycine chemistry is explored and routes to its formation, from the simplest compounds found in interstellar ices, are proposed.

Formation of NH2CHO and CH3CHO upon UV processing of interstellar ice analogs

2019 ◽  
Vol 15 (S350) ◽  
pp. 417-419
Author(s):  
Rafael Martín-Doménech ◽  
Karin I. Öberg ◽  
Mahesh Rajappan
Keyword(s):  
Vacuum Ultraviolet ◽  
Organic Molecules ◽  
Early Earth ◽  
Interstellar Ice ◽  
Interstellar Ices ◽  
Complex Organic

AbstractComplex organic molecules (COMs) may have played a role in the formation of life in the early Earth (Herbst & van Dishoeck (2009)). Here we present the formation of NH2CHO and CH3CHO upon vacuum-ultraviolet (VUV) irradiation of CO:NH3 and CO:CH4 ice mixtures, simulating the UV processing of interstellar ices in the interior of dense clouds. We have found that the conversion from ${\rm{N}}{{\rm{H}}_{\dot 2}}$ radicals to NH2CHO is 4–15 times higer than that from ${\rm{N}}{{\rm{H}}_{\dot 3}}$ to CH3CHO, probably due to the competing formation of larger hydrocarbons in the latter case.

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 Anharmonic Vibrational Frequencies and Spectroscopic Constants for the Detection of Ethynol in Space

2021 ◽  
Vol 7 ◽  
Author(s):  
Jax D. Dallas ◽  
Brent R. Westbrook ◽  
Ryan C. Fortenberry
Keyword(s):  
Interstellar Medium ◽  
Organic Molecules ◽  
Building Blocks ◽  
Spectroscopic Constants ◽  
Simultaneous Formation ◽  
Water Ice ◽  
Molecular Building Blocks ◽  
High Level ◽  
Complex Organic ◽  
Quantum Chemical Computations

The ethynol (HCCOH) molecule has recently been shown to be present in simulated astrochemical ices possibly linking it to molecular building blocks for interstellar complex organic molecules like amino acids. The proposed reaction mechanism suggests the simultaneous formation of both ketene and ethynol from mixed carbon monoxide/water ice in simulated interstellar conditions. Rigorous anharmonic spectral data within both the IR and microwave regions are needed for possible detection of ethynol in the interstellar medium. This study provides the first such data for this molecule from high-level quantum chemical computations where experiment is currently lacking. Ethynol has a Beff comparable to, but distinct from acetonitrile at 9,652.1 MHz and three notable infrared features with two in the hydride stretching-regions and the C–C stretch at 2,212.8 cm−1. The ketene isomer has already been detected in the interstellar medium, and the possible detection of ethynol made possible by this work may lead to a deeper understanding of the proposed ice formation mechanism involving both species and how this relates to the molecular origins of life.

scholarly journals Non-thermal desorption of complex organic molecules

2019 ◽  
Vol 627 ◽  
pp. A55 ◽  
Author(s):  
E. Dartois ◽  
M. Chabot ◽  
T. Id Barkach ◽  
H. Rothard ◽  
B. Augé ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Gas Phase ◽  
Thermal Desorption ◽  
Methyl Acetate ◽  
Vacuum Ultraviolet ◽  
Organic Molecules ◽  
Bulk Composition ◽  
Water Ice ◽  
Desorption Mechanism ◽  
Complex Organic

Context. The occurrence of complex organic molecules (COMs) in the gas phase at low temperature in the dense phases of the interstellar medium suggests that a non-thermal desorption mechanism is at work because otherwise, COMs should condense within a short timescale onto dust grains. Vacuum ultraviolet (VUV) photodesorption has been shown to be much less efficient for complex organic molecules, such as methanol, because mostly photoproducts are ejected. The induced photolysis competes with photodesorption for large COMs, which considerably lowers the efficiency to desorb intact molecules. Aims. We pursue an experimental work that has already shown that water molecules, the dominant ice mantle species, can be efficiently sputtered by cosmic rays. We investigate the sputtering efficiency of complex organic molecules that are observed either in the ice mantles of interstellar dense clouds directly by infrared spectroscopy (CH3OH), or that are observed in the gas phase by millimeter telescopes (CH3COOCH3) and that could be released from interstellar grain surfaces. Methods. We irradiated ice films containing complex organic molecules (methanol and methyl acetate) and water with swift heavy ions in the electronic sputtering regime. We monitored the infrared spectra of the film as well as the species released to the gas phase with a mass spectrometer. Results. We demonstrate that when methanol or methyl acetate is embedded in a water-ice mantle exposed to cosmic rays, a large portion is sputtered as an intact molecule, with a sputtering yield close to that of the main water-ice matrix. This must be even more true for the case of more volatile ice matrices, such as those that are embedded in carbon monoxide. Conclusions. Cosmic rays penetrating deep into dense clouds provide an efficient mechanism to desorb complex organic molecules. Compared to the VUV photons, which are induced by the interaction of cosmic rays, a large portion desorb as intact molecules with a proportion corresponding to the time-dependent bulk composition of the ice mantle, the latter evolving with time as a function of fluence due to the radiolysis of the bulk.

scholarly journals Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

2011 ◽  
Vol 532 ◽  
pp. A12 ◽  
Author(s):  
M. Lattelais ◽  
M. Bertin ◽  
H. Mokrane ◽  
C. Romanzin ◽  
X. Michaut ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Interstellar Ice ◽  
Ice Surfaces ◽  
Complex Organic

scholarly journals CARBON DIOXIDE INFLUENCE ON THE THERMAL FORMATION OF COMPLEX ORGANIC MOLECULES IN INTERSTELLAR ICE ANALOGS

2015 ◽  
Vol 809 (2) ◽  
pp. L18 ◽  
Author(s):  
V. Vinogradoff ◽  
F. Duvernay ◽  
N. Fray ◽  
M. Bouilloud ◽  
T. Chiavassa ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Organic Molecules ◽  
Interstellar Ice ◽  
Complex Organic

Photochemical Evolution of Interstellar/Precometary Organic Material

1997 ◽  
Vol 161 ◽  
pp. 23-47 ◽  
Author(s):  
Louis J. Allamandola ◽  
Max P. Bernstein ◽  
Scott A. Sandford
Keyword(s):  
Origin Of Life ◽  
Building Blocks ◽  
Complex Species ◽  
Infrared Observations ◽  
Interstellar Ice ◽  
Polycyclic Aromatic ◽  
Ultraviolet Photolysis ◽  
The Origin Of Life ◽  
Simple Molecules ◽  
Complex Organic

AbstractInfrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Since comets are thought to be a major source of the volatiles on the primative earth, their organic inventory is of central importance to questions concerning the origin of life. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, CH4, H2, and probably some NH3and H2CO, as well as more complex species including nitriles, ketones, and esters. The evidence for these, as well as carbonrich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon is briefly reviewed. This is followed by a detailed summary of interstellar/precometary ice photochemical evolution based on laboratory studies of realistic polar ice analogs. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(= O)NH2(formamide), CH3C(= O)NH2(acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including polyoxymethylene and related species (POMs), amides, and ketones. The ready formation of these organic species from simple starting mixtures, the ice chemistry that ensues when these ices are mildly warmed, plus the observation that the more complex refractory photoproducts show lipid-like behavior and readily self organize into droplets upon exposure to liquid water suggest that comets may have played an important role in the origin of life.

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