State selected ion–molecule reactions by a TESICO technique. X. O+2(v)+CH4

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Abstract
Vibrational state selected (relative) reaction cross sections have been determined for v=0–3 of the O+2 ion, for each of the three product channels of the reaction O+2(v)+CH4, viz. O+2(v)+CH4→CH3O+2+H (1) →CH+3+HO2 (2) →CH+4+O2 , (3) using the TESICO (threshold electron–secondary ion coincidence) technique. At a fixed collision energy of 0.27 eV, it has been found that the cross section of exoergic channel (1) increases most prominently with increasing vibrational quantum number v in the range v=0–2, but decreasees sharply in going from v=2 to v=3. The cross sections of endoergic channels (2) and (3) also increase with increasing v but their rates of increase are much smaller than that of channel (1) in the range v=0–2. When v is increased to 3, however, charge transfer channel (3) is enhanced dramatically and the CH+4 ion becomes the most abundant product ion. The cross section of channel (2) also increases more sharply in going from v=2 to v=3 than in the range v=0–2, but the CH+3 ion still remains the least abundant of the three product ions. As a result of these variations in the individual cross sections, the overall cross section for the O+2+CH4 reaction increases monotonically with increasing v throughout the range studied (v=0–3). The results are compared with that of the collision energy dependence as obtained in drift and flow‐drift experiments and the implications are discussed in conjunction with the structure of the CH3O+2 ion and the relevant potential energy surfaces.