Cosmic-Ray-DrivenChemistry in the CH₃CH₂OH/NH₃ InterstellarIce Analog

Ethyl alcohol (CH₃CH₂OH) and ammonia (NH₃) are prominent molecules in interstellar medium (ISM). Studying their astrochemically relevant reactions is crucial to advancing our understanding of astrochemical processes. To model astrochemically relevant ices on interstellar grain surfaces, pure CH₃CH₂OH, pure NH₃, and CH₃CH₂OH/NH₃ ices were deposited onto a cold substrate. The effects of cosmic ray irradiation, an important driver of ISM chemistry, were simulated by using 5 keV electron bombardment. Subsequently, the desorption of reaction products from the icy mantles into the gas phase was modeled through temperature-programed desorption (TPD). The compositional changes in the ice were continuously monitored during the TPD experiments. In separate experiments, desorbed molecules were captured and isolated in an Ar matrix for identification. Chemical changes were monitored by using Fourier transform infrared (FTIR) spectroscopy. Electron irradiation induced the formation of various species on the ices. For pure CH₃CH₂OH ice, the reaction products included CH₄, CH₃CH₃, CH₂CH₂, CH₃CH₂CH₃, CH₂CHOH, CH₂O, CH₃CHO, CH₂CO, CH₃C(O)CH₃, CH₃COOH, CO, CO₂, HĊO, H₂ĊOH, CH₃OH, CH₂CHCHO, and HCOOH. For pure NH₃ ice, the experimental results were consistent with previous studies. In the case of CH₃CH₂OH/NH₃ ice mixtures, in addition to the products detected in single-component experiments, the formation of N- and O-containing organic molecules such as acetamide (CH₃C(O)NH₂), formamide (NH₂CHO), and isocyanic acid (HNCO) was observed. These findings contribute to our understanding of the chemical evolution of prebiotic molecules in the ice phase of the ISM.