Interstellar dimethyl ether gas-phase formation: a quantum chemistry and kinetics study

Abstract

Dimethyl ether is one of the most abundant interstellar complex organic molecules. Yet its formation route remains elusive. In this work, we have performed electronic structure and kinetics calculations to derive the rate coefficients for two ion-molecule reactions recently proposed as a gas-phase formation route of dimethyl ether in interstellar objects, namelyA comparison with previous experimental rate coefficients for the reaction CH 3 OH + CH 3 OH + 2 sustains the accuracy of the present calculations and allow a more reliable extrapolation at the low temperatures of interest in interstellar objects (10-100 K). The rate coefficient for the reaction (CH 3 ) 2 OH + + NH 3 is, instead, provided for the first time ever. The rate coefficients derived in this work essentially confirm the prediction by Taquet et al. (2016) concerning dimethyl ether formation in hot cores/corinos. Nevertheless, this formation route cannot be efficient in cold objects (like prestellar cores) where dimethyl ether is also detected, because ammonia has a very low abundance in those environments.

The Role of State-of-the-Art Quantum-Chemical Calculations in Astrochemistry: Formation Route and Spectroscopy of Ethanimine as a Paradigmatic Case

“…For what concerns PST, it provides a useful, and easily implemented, reference theory for barrierless reactions, and it is largely used in computational kinetics applied to astrochemistry (see, for example, References [ 35 , 37 , 104 , 105 ]). Its assumption is that the interaction between the two reacting fragments is isotropic and does not affect the internal fragment motions.…”

Organic Complexity in Protostellar Disk Candidates

“…Later, in the hot corino stage, gasphase molecules emit from much warmer and denser regions, where most ice will have sublimated into the gas phase. Gas-phase compositions therefore reflect thermal ice desorption and possibly additional gas-phase chemistry (Herbst & van Dishoeck 2009;Balucani et al 2015;Skouteris et al 2017Skouteris et al , 2019. Finally, we can best explore COM chemistry at the Class II disk stage using cometary measurements, which are made in the gasphase but are believed to probe pristine ices.…”

Theoretical and Computational Analysis at a Quantum State Level of Autoionization Processes in Astrochemistry

“…In this paper it is applied to prototype atom-atom systems, and allows to rationalize in a unifying picture most of the available experimental findings from our and other laboratories. This opened the possibility to obtain state to state cross sections which is of great interest for the investigation of quantum effects in the coherent control of collision processes in astrochemistry, promoting Penning and associative ionization, from ultra-cold up to thermal reactive collisions [ 10 , 57 , 58 ]. Obtained results suggest also how to extend the methodology to autoionization reactions involving molecules [ 7 , 9 , 59 ], which are of great interest in several fields, including the balance of phenomena occurring in interstellar environments and planetary atmospheres.…”