Gas‐Grain Processes for the Formation of CH4and H2O: Reactions of H Atoms with C, O, and CO in the Solid Phase at 12 K

The reactions of H atoms with C, O, CO, and CH 3 CN in solid phase at 12 K were investigated by temperature-programmed mass spectrometry. In the reaction of H atoms with C atoms trapped in the CO matrix, H atoms migrate in the CO matrix and react with trapped C atoms selectively to form CH 4 . D 2 O was the major product from the reactions of D atoms with O atoms trapped in a N 2 O matrix. CH 4 was found to be one of the final products from the reactions of H atoms with solid CO. The precursor for the formation of CH 4 may be the CH 2 OH radical. No products were detected from the reaction of H atoms with CH 3 CN, suggesting that the nitrile group is not amenable to the hydrogenation reactions by H atoms at 12 K. When CH 4 molecules are trapped in matrices such as CH 3 OH and H 2 O, the desorption of CH 4 is greatly suppressed, i.e., from ~50 K for neat CH 4 to ~100 K for CH 4 in the CH 3 OH matrix and to ~150 K for CH 4 in the H 2 O matrix.