A systematic IR and VUV spectroscopic investigation of ion, electron, and thermally processed ethanolamine ice

Zhang, Jin and Muiña, Alejandra Traspas and Mifsud, Duncan and Kaňuchová, Zuzana and Cielinska, Klaudia and Herczku, Péter and Kumar Kushwaha, Rahul and Kovács, Sándor and Rácz, Richárd Péter and Santos, Julia C and Hopkinson, Alfred T and Craciunescu, Luca and Jones, Nykola C and Hoffmann, Søren V and Biri, Sándor and Vajda, István K. and Rajta, István and Dawes, Anita and Sivaraman, Bhalamurugan and Juhász, Zoltán and Sulik, Béla and Linnartz, Harold and Hornekær, Liv and Fantuzzi, Felipe and Mason, Nigel J. and Ioppolo, Sergio (2024) A systematic IR and VUV spectroscopic investigation of ion, electron, and thermally processed ethanolamine ice. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 533 (1). pp. 826-840. ISSN 0035-8711

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Abstract

The recent detection of ethanolamine (EtA, HOCHCHNH), a key component of phospholipids, i.e. the building blocks of cell membranes, in the interstellar medium is in line with an exogenous origin of life-relevant molecules. However, the stability and survivability of EtA molecules under inter/circumstellar and Solar System conditions have yet to be demonstrated. Starting from the assumption that EtA mainly forms on interstellar ice grains, we have systematically exposed EtA, pure and mixed with amorphous water (HO) ice, to electron, ion, and thermal processing, representing ‘energetic’ mechanisms that are known to induce physicochemical changes within the ice material under controlled laboratory conditions. Using infrared (IR) spectroscopy, we have found that heating of pure EtA ice causes a phase change from amorphous to crystalline at 180 K, and further temperature increase of the ice results in sublimation-induced losses until full desorption occurs at about 225 K. IR and vacuum ultraviolet (VUV) spectra of EtA-containing ices deposited and irradiated at 20 K with 1 keV electrons as well as IR spectra of HO:EtA mixed ice obtained after 1 MeV He ion irradiation have been collected at different doses. The main radiolysis products, including HO, CO, CO, NH, and CHOH, have been identified and their formation pathways are discussed. The measured column density of EtA is demonstrated to undergo exponential decay upon electron and ion bombardment. The half-life doses for electron and He ion irradiation of pure EtA and HO:EtA mixed ice are derived to range between eV/16u. Extrapolating these results to space conditions, we conclude that EtA mixed in HO ice is more stable than in pure form and it should survive throughout the star and planet formation process.

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