Formation of complex chemical species in astrochemistry (a review)

Shematovich, V. I.

doi:10.1134/s0038094612060068

Cited by 17 publications

(7 citation statements)

References 54 publications

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“…The modelling of intense excitation processes in lowtemperature ices has found applications in a wide variety of fields [1], but particularly in molecular astrophysics where such processes may lead to novel chemistry within the ice structure [2][3][4][5]. Interstellar and planetary ices may be modelled as dense gases experiencing weak intermolecular forces of attraction and restricted degrees of freedom.…”

Section: Introductionmentioning

confidence: 99%

Electron irradiation and thermal chemistry studies of interstellar and planetary ice analogues at the ICA astrochemistry facility

et al. 2021

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The modelling of molecular excitation and dissociation processes relevant to astrochemistry requires the validation of theories by comparison with data generated from laboratory experimentation. The newly commissioned Ice Chamber for Astrophysics-Astrochemistry (ICA) allows for the study of astrophysical ice analogues and their evolution when subjected to energetic processing, thus simulating the processes and alterations interstellar icy grain mantles and icy outer Solar System bodies undergo. ICA is an ultra-high vacuum compatible chamber containing a series of IR-transparent substrates upon which the ice analogues may be deposited at temperatures of down to 20 K. Processing of the ices may be performed in one of three ways: (i) ion impacts with projectiles delivered by a 2 MV Tandetron-type accelerator, (ii) electron irradiation from a gun fitted directly to the chamber, and (iii) thermal processing across a temperature range of 20–300 K. The physico-chemical evolution of the ices is studied in situ using FTIR absorbance spectroscopy and quadrupole mass spectrometry. In this paper, we present an overview of the ICA facility with a focus on characterising the electron beams used for electron impact studies, as well as reporting the preliminary results obtained during electron irradiation and thermal processing of selected ices. Graphic Abstract

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Section: Introductionmentioning

confidence: 99%

Electron irradiation and thermal chemistry studies of interstellar and planetary ice analogues at the ICA astrochemistry facility

et al. 2021

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“…For example, Holmström et al (2008) and Ekenbäck et al (2010) suggested that the escaping planetary atoms are ionized by the SW through chargeexchange with the SW protons giving origin to energetic neutral atoms (ENAs). A variety of other photochemical reactions occurs along with the radiative heating, ionization, recombination, and ENAs production (Yelle 2004;Shematovich 2012;Guo 2011Guo , 2013. Understanding the expansion and escape occurring in the atmosphere of close-in exoplanets requires the study of the complex interconnection between SW and planetary wind (PW; Shaikhislamov et al 2014Khodachenko et al 2012Khodachenko et al , 2015Khodachenko et al , 2017.…”

Section: Introductionmentioning

confidence: 99%

Modelling atmospheric escape and Mg ii near-ultraviolet absorption of the highly irradiated hot Jupiter WASP-12b

Dwivedi

Khodachenko

Шайхисламов

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present two-dimensional multi-fluid numerical modelling of the upper atmosphere of the hot Jupiter WASP-12b. The model includes hydrogen chemistry, and self-consistently describes the expansion of the planetary upper atmosphere and mass loss due to intensive stellar irradiation, assuming a weakly magnetized planet. We simulate the planetary upper atmosphere and its interaction with the stellar wind (SW) with and without the inclusion of tidal force and consider different XUV irradiation conditions and SW parameters. With the inclusion of tidal force, even for a fast SW, the escaping planetary material forms two streams, propagating towards and away from the star. The atmospheric escape and related mass loss rate reaching the value of 10 12 gs -1 appear to be mostly controlled by the stellar gravitational pull. We computed the column density and dynamics of MgII ions considering three different sets of SW parameters and XUV fluxes. The simulations enable to compute the absorption at the position of the Mg h line and to reproduce the times of ingress and egress. In case of a slow SW and without accounting for tidal force, the high orbital velocity leads to the formation of a shock approximately in the direction of the planetary orbital motion. In this case, mass loss is proportional to the stellar XUV flux. At the same time, ignoring of tidal effects for WASP-12b is a strong simplification, so the scenario with a shock, altogether is an unrealistic one.Keywords: planets and satellites: individual: exoplanetplanets and satellites: gaseous planetsplanets and satellites: atmosphereplanets and satellites: dynamical evolution and stabilityplanets and satellites: atmosphereplanet-star interactions

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“…Molecules form in the interstellar medium provided it is dense enough for collisions to bring the chemical reactants together and cool enough to suppress the complete dissociation of chemical products. Observations of the interstellar medium in and outside of our galaxy have revealed a rich and diverse chemistry (Shematovich 2012), spanning across a wide range of physical environments. As stars form through the collapse of overdensities inside this optically opaque dense interstellar medium (Young & Scoville 1991), the study of molecular gas can provide a window into the star-formation process and shed light onto the lifecycle of galaxies.…”

Section: Introductionmentioning

confidence: 99%

Incorporating astrochemistry into molecular line modelling via emulation

Mijolla

Viti

Holdship

et al. 2019

A&A

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In studies of the interstellar medium in galaxies, radiative transfer models of molecular emission are useful for relating molecular line observations back to the physical conditions of the gas they trace. However, doing this requires solving a highly degenerate inverse problem. In order to alleviate these degeneracies, the abundances derived from astrochemical models can be converted into column densities and fed into radiative transfer models. This enforces that the molecular gas composition used by the radiative transfer models be chemically realistic. However, because of the complexity and long running time of astrochemical models, it can be difficult to incorporate chemical models into the radiative transfer framework. In this paper, we introduce a statistical emulator of the UCLCHEM astrochemical model, built using neural networks. We then illustrate, through examples of parameter estimations, how such an emulator can be applied on real and synthetic observations.

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Formation of complex chemical species in astrochemistry (a review)

Cited by 17 publications

References 54 publications

Electron irradiation and thermal chemistry studies of interstellar and planetary ice analogues at the ICA astrochemistry facility

Electron irradiation and thermal chemistry studies of interstellar and planetary ice analogues at the ICA astrochemistry facility

Modelling atmospheric escape and Mg ii near-ultraviolet absorption of the highly irradiated hot Jupiter WASP-12b

Incorporating astrochemistry into molecular line modelling via emulation

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