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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 H2O/CH4 ice was studied by infrared (IR) spectroscopy and thermal desorption spectrometry (TDS). CH3OH was formed as a major product along with H2CO, C2H4, C2H6, and C2H2 as minor products when the mixed H2O/CH4 (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, CH3 + OH → CH3OH, and the insertion reaction, CH2 + H2O → CH3OH. One CH3OH molecule was formed per 60 electron irradiations with an electron energy of 100 eV. By using mixed H2O/CD4 ice, it was confirmed that formaldehyde was formed by the insertion reaction, C + H2O → H2CO.

Simulation experiments for the formation of CH3OH, HNC/HCN, and NH3 in solid‐phase reactions were performed. CH3OH and H2CO were formed as major products from the 100 eV electron‐irradiated mixed CH4/H2O solid at 10 K. There found to be two pathways for the formation of methanol with about equal importance, i.e., the recombination reaction: CH3 + OH → CH3OH, and the insertion reaction: CH2+H2O → CH3OH. One CH3OH molecule was formed per 60 electron irradiation with the electron energy of 100 eV. By using mixed H2O/CD4 ice, it was confirmed that formaldehyde was formed by the insertion reaction, C + H2O →H2CO.A mixed gas of N2/HCN (50/1) at a few Torr was activated by a dc discharge and was deposited on the gold‐plated copper substrate at 10, 15, and 20 K. During the deposition of plasma‐activated sample gas, D atoms produced by the dc discharge of D2 were simultaneously sprayed over the solid film. The association reactions of CN with D at 10 K were found to generate DNC and DCN with the intensity ratio DN...