Slow-electron-triggered Chemistry In Interstellar Methanol-water Ices

[Astronomy & Astrophysics] Water and, to a lesser extent, methanol are widespread in interstellar space as ices, where sustained exposure to ionizing radiation promotes the formation of complex compounds such as prebiotic molecules via multi-step reactions.

Although UV photolysis processes of methanol-containing ices yield diverse molecular products, the contribution of low-energy electrons, abundantly generated along the ionization tracks of cosmic rays, remains largely unexplored with respect to driving chemical evolution in mixed water–methanol ices.

Here, we report an experimental investigation of the low-energy (< 12 eV) electron irradiation of water:d3-methanol ices, revealing the first direct evidence of the formation of methanediol.

Using isotopic labelling with deuterated methanol to ensure clear mass discrimination, we identified and quantified this new synthesized neutral product, which emerges above 5 eV and peaks at 7–8 eV. The observed energy dependence associates the initial process to dissociative electron attachment to water and methanol.

These results uncover a previously unrecognized electron-driven route to methanediol synthesis in astrophysical ices, underscoring the broader role of secondary electrons in cosmic organic chemistry.

Slow-electron-triggered chemistry in interstellar methanol-water ices, Astronomy & Astrophysics

Astrobiology, Astronomy, Astrochemistry, Interstellar,