Non-thermal desorption of complex organic molecules: Cosmic-ray sputtering of CH3OH embedded in CO2 ice

Abstract

Methanol ice is embedded in interstellar ice mantles present in dense molecular clouds. We aim to measure the sputtering efficiencies starting from different ice mantles of varying compositions experimentally, in order to evaluate their potential impact on astrochemical models. The sputtering yields of complex organic molecules is of particular interest, since few mechanisms are efficient enough to induce a significant feedback to the gas phase. We irradiated methanol and carbon dioxide ice mixtures of varying ratios with swift heavy ions in the electronic sputtering regime. We monitored the evolution of the infrared spectra and the species released to the gas phase with a mass spectrometer. Methanol and 13C-methanol isotopologue were used to remove any ambiguity on the measured irradiation products. The sputtering of methanol embedded in carbon dioxide ice is an efficient process leading to the ejection of intact methanol in the gas phase. We establish that when methanol is embedded in a carbon-dioxide-rich mantle exposed to cosmic rays, a significant fraction is sputtered as intact molecules. The sputtered fraction follows the time-dependent bulk composition of the ice mantle, the latter evolving with time due to the radiolysis-induced evolution of the bulk. If methanol is embedded in a carbon dioxide ice matrix, as the analyses of the spectral shape of the CO2 bending mode observations in some lines of sight suggest, the overall methanol sputtering yield is higher than if embedded in a water ice mantle. The sputtering is increased by a factor close to the dominant ice matrix sputtering yield, which is about six times higher for pure carbon dioxide ice when compared to water ice. These experiments are further constraining the cosmic-ray-induced ice mantle sputtering mechanisms important role in the gas-phase release of complex organic molecules from the interstellar solid phase.

arXiv admin note: text overlap with arXiv:1906.03084

References in corpus (3)

• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• Formation of Complex Molecules in Prestellar Cores: a Multilayer Approach
• Heavy ion irradiation of crystalline water ice

Cited by in corpus (13)

• The complex organic molecular content in the L1498 starless core
• A study of submillimeter methanol absorption toward PKS1830-211: Excitation, invariance of the proton-electron mass ratio, and systematics
• Complex organic molecules in protoplanetary disks : X-ray photodesorption from methanol-containing ices. Part I -- Pure methanol ices
• Modelling methanol and hydride formation in the JWST Ice Age era
• Spectroscopic measurements of CH${}_3$OH in layered and mixed interstellar ice analogues
• Complex organic molecules uncover deeply embedded precursors of hot cores
• Photochemistry of interstellar ice forming Complex Organic Molecules
• Constraints on the non-thermal desorption of methanol in the cold core LDN 429-C
• Radiation sputtering of hydrocarbon ices at Europa-relevant temperatures
• Cosmic-ray induced sputtering of interstellar formaldehyde ices
• Chemical constraints on the dynamical evolution of the cold core L694
• Pulsed ion deflection to overcome detector saturation in cryogenic ice sampling
• Infrared observations of the flaring maser source G358.93-0.03 -- SOFIA confirms an accretion burst from a massive young stellar object