Measurements of Low Temperature Rate Coefficients for the Reaction of CH with CH<sub>2</sub>O and Application to Dark Cloud and AGB Stellar Wind Models

West, Niclas A.; Millar, T. J.; Sande, M. Van de; Rutter, Edward; Blitz, Mark A.; Decin, L.; Heard, Dwayne E.

doi:10.3847/1538-4357/ab480e

Cited by 16 publications

(24 citation statements)

References 60 publications

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“…[96][97][98][99] There have been significant advances in low-temperature studies of reactions involving radicals and oxygenated volatile organic compounds or complex organic molecules. Systems that have received particular attention include reactions such as OH + CH 3 OH, OH + CH 3 CHO, OH + CH 3 C(O)CH 3 , and CH + H 2 CO. [100][101][102][103][104][105][106][107][108][109][110][111] While many of these CRESU studies have focused on the measurement of rate coefficients, in several cases interesting reaction dynamics were also observed. For example, several OH reaction pathways that involved tunnelling through the abstraction activation barrier were found to yield rate coefficients independent of pressure.…”

Section: Flow Tube Methodsmentioning

confidence: 99%

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Miossec

Heazlewood

2022

Chem. Commun.

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Section: Flow Tube Methodsmentioning

confidence: 99%

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Miossec

Heazlewood

2022

Chem. Commun.

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“…First, the reverse rate constant k −2,∞ for H + NNH association was assessed via classical capture theory based on a -C 6 /r 6 potential. We estimate that dipole-induced dipole interactions contribute −2.6 • 10 −79 J m 6 to C 6 , with a dominant contribution of −17.7 • 10 −79 J m 6 from dispersion forces, which leads [45] to k −2,∞ = 2.5 • 10 14 T 1/6 cm 3 mol −1 s −1 . The high-pressure limit in the forward direction k 2,∞ was found via the association kinetics and the computed equilibrium constant.…”

mentioning

confidence: 88%

New reactions of diazene and related species for modelling combustion of amine fuels

2021

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Potential energy surfaces for reactions involving N 2 H 2 isomers of diazene (diimide) have been explored using density functional theory, with energies based on coupled-cluster theory. A focus is on processes that create or consume these species, and isomerization between the E (trans) and Z (cis) forms of HNNH.These include isomerization and dissociation pathways for HNNH, addition of H atoms to form N 2 H 3 , abstraction by H atoms yielding short-lived NNH, and abstraction reactions of H with N 2 H 3 . Transition state and capture theories are applied for high-pressure-limiting behavior, while low-pressure and fallo regions are characterized via the methods of Troe and coworkers. Rate constants and thermochemistry are provided to improve models of diamine chemistry, relevant to the combustion of NH 3 especially at high concentrations, high pressures or under reducing conditions. Results indicate that amine radical recombination mainly yields the E HNNH isomer, while H-abstraction from N 2 H 3 results in E HNNH and H 2 NN. However, at elevated temperature E → Z isomerization becomes competitive, and Z HNNH, being more reactive, acts to enhance the diazene consumption rate.

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“…The atomium observations also serve as a guide for new laboratory kinetic measurements, and quantum chemical calculations of accurate theoretical structures and kinetic reaction rates needed to assess the relevant gas phase reaction rates in prior and newly developed chemical kinetic codes (e.g., Gobrecht et al 2018;West et al 2019;McCarthy et al 2019;Boulangier et al 2019;Escatllar & Bromley 2020). The first paper resulting from these observations entails a detailed analysis of the rotational spectra of the aluminium halides in W Aql, augmented with supplementary observations from Herschel (Danilovich et al 2021).…”

Section: Dust Nucleationmentioning

confidence: 99%

ATOMIUM: ALMA tracing the origins of molecules in dust forming oxygen rich M-type stars

Gottlieb

Decin

Richards

et al. 2022

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This overview paper presents ATOMIUM, a Large Programme in Cycle 6 with the Atacama Large Millimeter/submillimeter Array (ALMA). The goal of ATOMIUM is to understand the dynamics and the gas phase and dust formation chemistry in the winds of evolved asymptotic giant branch (AGB) and red supergiant (RSG) stars. A more general aim is to identify chemical processes applicable to other astrophysical environments. Seventeen oxygen-rich AGB and RSG stars spanning a range in (circum)stellar parameters and evolutionary phases were observed in a homogeneous observing strategy allowing for an unambiguous comparison. Data were obtained between 213.83 and 269.71 GHz at high (∼0″.025–0″.050), medium (∼0″.13–0″.24), and low (∼1″) angular resolution. The sensitivity per ∼1.3 km s−1 channel was 1.5–5 mJy beam−1, and the line-free channels were used to image the millimetre wave continuum. Our primary molecules for studying the gas dynamics and dust formation are CO, SiO, AlO, AlOH, TiO, TiO2, and HCN; secondary molecules include SO, SO2, SiS, CS, H2O, and NaCl. The scientific motivation, survey design, sample properties, data reduction, and an overview of the data products are described. In addition, we highlight one scientific result – the wind kinematics of the ATOMIUM sources. Our analysis suggests that the ATOMIUM sources often have a slow wind acceleration, and a fraction of the gas reaches a velocity which can be up to a factor of two times larger than previously reported terminal velocities assuming isotropic expansion. Moreover, the wind kinematic profiles establish that the radial velocity described by the momentum equation for a spherical wind structure cannot capture the complexity of the velocity field. In fifteen sources, some molecular transitions other than 12CO v = 0 J = 2 − 1 reach a higher outflow velocity, with a spatial emission zone that is often greater than 30 stellar radii, but much less than the extent of CO. We propose that a binary interaction with a (sub)stellar companion may (partly) explain the non-monotonic behaviour of the projected velocity field. The ATOMIUM data hence provide a crucial benchmark for the wind dynamics of evolved stars in single and binary star models.

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Measurements of Low Temperature Rate Coefficients for the Reaction of CH with CH₂O and Application to Dark Cloud and AGB Stellar Wind Models

Cited by 16 publications

References 60 publications

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Low-temperature reaction dynamics of paramagnetic species in the gas phase

New reactions of diazene and related species for modelling combustion of amine fuels

ATOMIUM: ALMA tracing the origins of molecules in dust forming oxygen rich M-type stars

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Measurements of Low Temperature Rate Coefficients for the Reaction of CH with CH2O and Application to Dark Cloud and AGB Stellar Wind Models

Cited by 16 publications

References 60 publications

Low-temperature reaction dynamics of paramagnetic species in the gas phase

Low-temperature reaction dynamics of paramagnetic species in the gas phase

New reactions of diazene and related species for modelling combustion of amine fuels

ATOMIUM: ALMA tracing the origins of molecules in dust forming oxygen rich M-type stars

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Product

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Measurements of Low Temperature Rate Coefficients for the Reaction of CH with CH₂O and Application to Dark Cloud and AGB Stellar Wind Models