Investigating solid-state CH3OH formation with chemical modelling

Abstract

Context. Recent Monte Carlo simulations and laboratory studies of interstellar ices have proposed an alternative pathway involving the radical-molecule H-atom abstraction reaction in the overall mechanism of methanol (CH3OH) formation in dark molecular clouds. Aims. A computational study was conducted to investigate the contribution of the radical-molecule H-atom abstraction route in CH3OH formation in interstellar ices, both in non-shocked and shocked environments, and to examine how the physical conditions of the interstellar medium (ISM) affect the overall CH3OH synthesis pathway. Methods. A set of chemical models were ran using the gas-grain chemical code UCLCHEM to systematically explore methanol synthesis in various physical scenarios, including non-shock and low- and high-velocity C-shocks. Results. This work demonstrated for the first time that, under non-shock and shocked-influenced environments, the primary reaction leading to the formation of methanol in the inner layers of interstellar ices is indeed the radical-molecule H-atom abstraction route. However, such route is dependent on the gas kinetic temperature (Tk), gas volume density (nH2 ), velocity of the C-shock wave (vshock), and cosmic ray ionisation rate (ζ). Furthermore, gaseous formaldehyde may trace C-type shocks and serve to differentiate methanol formation pathways in low-velocity C-shocked environments, as its abundance varies more significantly than that of CH3OH with the inclusion of the H-atom abstraction reaction in UCLCHEM. The H2CO/CH3OH ratio thus represents a potential diagnostic tool for this purpose.

References in corpus (22)

• The UMIST database for astrochemistry 2012
• A KInetic Database for Astrochemistry (KIDA)
• An Ice Age JWST inventory of dense molecular cloud ices
• Evaporation of ices near massive stars: models based on laboratory TPD data
• Simulation of the Formation and Morphology of Ice Mantles on Interstellar Grains
• H-atom addition and abstraction reactions in mixed CO, H2CO and CH3OH ices: an extended view on complex organic molecule formation
• Dust as interstellar catalyst I. Quantifying the chemical desorption process
• Parametrization of C-shocks. Evolution of the Sputtering of Grains
• UCLCHEM: A Gas-Grain Chemical Code
• Simultaneous Hydrogenation and UV-photolysis Experiments of NO in CO-rich Interstellar Ice Analogues; linking HNCO, OCN-, NH2CHO and NH2OH
• Glycolaldehyde Formation via the Dimerisation of the Formyl Radical
• Formation of COMs through CO hydrogenation on interstellar grains
• Reactive Desorption of CO Hydrogenation Products under Cold Pre-stellar Core Conditions
• Formation of interstellar methanol ice prior to the heavy CO freeze-out stage
• Hydrogen transfer reactions of interstellar Complex Organic Molecules
• First experimental confirmation of the CH3O + H2CO -> CH3OH + HCO reaction: expanding the CH3OH formation mechanism in interstellar ices
• Observations of CH${}_3$OH and CH${}_3$CHO in a Sample of Protostellar Outflow Sources
• Warm Cores around Regions of Low-Mass Star Formation
• Tracing shock type with chemical diagnostics: an application to L1157
• Modelling methanol and hydride formation in the JWST Ice Age era
• Diagnosing shock temperature with NH${}_3$ and H${}_2$O profiles
• Tracing the chemical footprint of shocks in AGN-host and starburst galaxies with ALMA multi-line molecular studies

Cited by in corpus (1)

• Shock-type inference of L1157 B2 using methanol desorption