Guided ion–beam studies of the ground-state O+2 (2Πg, v=0) reaction with CH4: Effect of internal versus translational energy

Guided ion-beam mass spectrometry is used to study the reactions of methane with O+2 in its ground electronic and vibrational state. In addition to the three previously reported reaction products, CH2OOH+, CH+3, and CH+4, we also observe three other products, CH2O+2, H3O+, and CO+2 . Reactions of excited O+2 ions are also examined and are shown to be more efficient than those for ground-state ions. The thermochemistry and potential-energy surfaces for this reaction are discussed as well as the effects of vibrational, electronic, and translational energy on the reaction system. A heat of formation for CH2O+2 of 201.5±1.6 kcal/mol is measured and tentatively assigned to the methyne hydroperoxy ion structure, HC–O–OH+.