State selected ion–molecule reactions by a TESICO technique. VI. Vibronic-state dependence of the cross sections in the reactions O+2(X 2Πg, v; a 4Πu, v)+H2→ O2H++H, H+2+O2

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Abstract
The threshold electron‐secondary ion coincidence (TESICO) technique has been utilized to select the vibronic states of the O+2 reactant ions in the endoergic reactions O+2+H2→O2H++H(1) and O+2+H2→H+2+O2(2). The vibronic states selected were X 2Πg, v=19, 20 and a 4Πu, v=0–8, for each of which the relative reaction cross sections have been determined. It has been found that while reaction (1) indeed proceeds with the ground X 2Πg state ions by the vibrational excitation (at collision energies lower than the translational threshold), it is considerably (an order of magnitude) enhanced by the electronic excitation of the reactant ions to a 4Πu. When vibrational energy is added to the a 4Πu state, the cross section of reaction (1) further rises sharply (by a factor of 2) at v=2 and then decreases more slowly, reaching the original (v=0) value at v=4. After that, the cross section apparently decreases by about a factor of 2 at v=8. The cross section of reaction (2) behaves in a manner similar to that of reaction (1) as a function of vibrational quantum number. The magnitudes of the cross sections for both electronic states are, however, consistently smaller than those of reaction (1) by roughly a factor of 10.