Methanol Formation from Electron‐irradiated Mixed H2O/CH4Ice at 10 K

In order to investigate the role of cosmic rays in the formation of methanol on dust grains, low-energy electron irradiation (~10-300 eV) on mixed H 2 O/CH 4 ice was studied by infrared (IR) spectroscopy and thermal desorption spectrometry (TDS). CH 3 OH was formed as a major product along with H 2 CO, C 2 H 4 , C 2 H 6 , and C 2 H 2 as minor products when the mixed H 2 O/CH 4 (10/1) ice was irradiated by electrons at 10 K. There were found to be two pathways for the formation of methanol with about equal importance, i.e., the recombination reaction, CH 3 + OH → CH 3 OH, and the insertion reaction, CH 2 + H 2 O → CH 3 OH. One CH 3 OH molecule was formed per 60 electron irradiations with an electron energy of 100 eV. By using mixed H 2 O/CD 4 ice, it was confirmed that formaldehyde was formed by the insertion reaction, C + H 2 O → H 2 CO.