Formation of methyl formate after cosmic ion irradiation of icy grain mantles

Modica, Paola; Palumbo, M. E.

doi:10.1051/0004-6361/201014101

Cited by 92 publications

(109 citation statements)

References 39 publications

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“…We note that of the species we are modelling, only methyl formate and methyl cyanide have been extensively studied in the laboratory (Modica & Palumbo 2010;Bennett & Kaiser 2007;Khlifi et al 1996;Defrees et al 1985;Huntress & Mitchell 1979). The other complex molecules are little-known and it is very likely that our models are missing routes of formation and destruction for these species.…”

Section: Discussionmentioning

confidence: 99%

A high-resolution study of complex organic molecules in hot cores

Calcutt

Viti

Codella

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We present the results of a line identification analysis using data from the IRAM Plateau de Bure Inferferometer, focusing on six massive star-forming hot cores: G31.41+0.31, G29.96-0.02, G19.61-0.23, G10.62-0.38, G24.78+0.08A1 and G24.78+0.08A2. We identify several transitions of vibrationally excited methyl formate (HCOOCH 3 ) for the first time in these objects as well as transitions of other complex molecules, including ethyl cyanide (C 2 H 5 CN), and isocyanic acid (HNCO). We also postulate a detection of one transition of glycolaldehyde (CH 2 (OH)CHO) in two new hot cores. We find G29.96-0.02, G19.61-0.23, G24.78+0.08A1 and G24.78+0.08A2 to be chemically very similar. G31.41+0.31, however, is chemically different: it manifests a larger chemical inventory and has significantly larger column densities. We suggest that it may represent a different evolutionary stage to the other hot cores in the sample, or it may surround a star with a higher mass. We derive column densities for methyl formate in G31.41+0.31, using the rotation diagram method, of 4×10 17 cm −2 and a T rot of ∼170 K. For G29.96-0.02, G24.78+0.08A1 and G24.78+0.08A2, glycolaldehyde, methyl formate and methyl cyanide all seem to trace the same material and peak at roughly the same position towards the dust emission peak. For G31.41+0.31, however, glycolaldehyde shows a different distribution to methyl formate and methyl cyanide and seems to trace the densest, most compact inner part of hot cores.

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Section: Discussionmentioning

confidence: 99%

A high-resolution study of complex organic molecules in hot cores

Calcutt

Viti

Codella

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…For instance, in the case of the AA/MF isomer couple, laboratory experiments have shown that different chemical routes are involved in the formation of each isomer. MF (and to a lower extent glycoaldehyde) can be synthesized from electron or proton irradiation of condensed mixtures of CO and CH 3 OH (Bennett & Kaiser 2007;Modica & Palumbo 2010), whereas the formation of acetic acid involves irradiation of CH 4 :CO 2 mixed ices, via a different mechanism (Bennett & Kaiser 2007). Both the chemical mechanism efficiency and the stoechiometry of the ices should have an important impact on the relative amount of isomers formed in the icy mantles.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

Lattelais

Bertin

Mokrane

et al. 2011

A&A

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Context. Over 20 of the ∼150 different species detected in the interstellar and circumstellar media have also been identified in icy environments. For most of the species observed so far in the interstellar medium (ISM), the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle -MEP) with few exceptions such as, for example, CH 3 COOH/HCOOCH 3 and CH 3 CH 2 OH/CH 3 OCH 3 , whose formation is thought to occur on the icy mantles of interstellar grains. Aims. We investigate whether differences found in the compositions of molecular ices and the surrounding gas phase could originate from differences between the adsorption of one isomer from that of another at the ice surface. Methods. We performed a coherent and concerted theoretical/experimental study of the adsorption energies of the four molecules mentioned above, i.e. acetic acid (AA)/methyl formate (MF) and ethanol (EtOH)/dimethyl ether (DME) on the surface of water ice at low temperature. The question was first addressed theoretically at LCT using solid state periodic density functional theory (DFT) to represent the organized solid support. The experimental determination of the ice/molecule interaction energies was then carried out independently by two teams at LPMAA and LERMA/LAMAp using temperature programmed desorption (TPD) under an ultra-high vacuum (UHV) between 70 and 160 K. Results. For each pair of isomers, theory and experiments both agree that the most stable isomer (AA or EtOH) interacts more efficiently with the water ice than the higher energy isomer (MF or DME). This differential adsorption can be clearly seen in the different desorption temperatures of the isomers. It is not related to their intrinsic stability but instead to both AA and EtOH producing more and stronger hydrogen bonds with the ice surface. Conclusions. We show that hydrogen bonding may play an important role in the release of organic species from grains and propose that, depending on the environment, differential adsorption should not be rejected as a possible way of interpreting MEP exceptions.

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“…This correction takes into account the longer path length of the IR beam at an incidence angle θ i = 45 deg (Fulvio et al 2009;Modica & Palumbo 2010).…”

Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

The influence of temperature on the synthesis of molecules on icy grain mantles in dense molecular clouds

Garozzo

Rosa

Kaňuchová

et al. 2011

A&A

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Context. Infrared observations show the presence of icy mantles along the line of sight toward young stellar objects (YSOs), where a temperature gradient is expected and indirectly observed. In this environment, icy mantles are affected by ion and UV irradiation. Laboratory experiments show that molecules are formed after irradiation of icy mixtures. However, most of the experiments done so far have been performed in the temperatures range of 10-20 K. Aims. To extend previous work we irradiated some icy mixtures, namely H 2 O:CO=10:1, H 2 O:CH 4 =4:1, and H 2 O:CO 2 =3:1 at two different temperatures (12 K and 40 or 60 K) to study the effects of temperature on the synthesis of molecules and the decrease in their parent species after ion irradiation. Methods. The experiments were performed in a high-vacuum chamber (P < 10 −7 mbar), where icy samples were irradiated with 30 keV He + ions and analyzed by a FTIR spectrophotometer. Infrared spectra of the samples were recorded after various steps of irradiation. Results. We found that the temperature affects the behavior of the volatile species (i.e., CO and CH 4 ) during irradiation. As a consequence, the production of molecular species is generally more prevalent at 12 K than at either 40 or 60 K, while the decrease in their parent volatile species is faster at high temperature. Conclusions. We conclude that the behavior of each species depends on the value of its sublimation temperature with respect to the temperature of the sample. If this latter is higher than the sublimation temperature of a given species, then the effects of thermal desorption compete with those due to irradiation.

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Formation of methyl formate after cosmic ion irradiation of icy grain mantles

Cited by 92 publications

References 39 publications

A high-resolution study of complex organic molecules in hot cores

A high-resolution study of complex organic molecules in hot cores

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

The influence of temperature on the synthesis of molecules on icy grain mantles in dense molecular clouds

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